[safe/jmp/linux-2.6] / fs / ext4 / super.c

/*
 *  linux/fs/ext4/super.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller (davem@caip.rutgers.edu), 1995
 */

#include <linux/module.h>
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/vmalloc.h>
#include <linux/jbd2.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/blkdev.h>
#include <linux/parser.h>
#include <linux/smp_lock.h>
#include <linux/buffer_head.h>
#include <linux/exportfs.h>
#include <linux/vfs.h>
#include <linux/random.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/quotaops.h>
#include <linux/seq_file.h>
#include <linux/proc_fs.h>
#include <linux/ctype.h>
#include <linux/log2.h>
#include <linux/crc16.h>
#include <asm/uaccess.h>

#include "ext4.h"
#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"

#define CREATE_TRACE_POINTS
#include <trace/events/ext4.h>

static int default_mb_history_length = 1000;

module_param_named(default_mb_history_length, default_mb_history_length,
                   int, 0644);
MODULE_PARM_DESC(default_mb_history_length,
                 "Default number of entries saved for mb_history");

struct proc_dir_entry *ext4_proc_root;
static struct kset *ext4_kset;

static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
                             unsigned long journal_devnum);
static int ext4_commit_super(struct super_block *sb, int sync);
static void ext4_mark_recovery_complete(struct super_block *sb,
                                        struct ext4_super_block *es);
static void ext4_clear_journal_err(struct super_block *sb,
                                   struct ext4_super_block *es);
static int ext4_sync_fs(struct super_block *sb, int wait);
static const char *ext4_decode_error(struct super_block *sb, int errno,
                                     char nbuf[16]);
static int ext4_remount(struct super_block *sb, int *flags, char *data);
static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf);
static int ext4_unfreeze(struct super_block *sb);
static void ext4_write_super(struct super_block *sb);
static int ext4_freeze(struct super_block *sb);


ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,
                               struct ext4_group_desc *bg)
{
        return le32_to_cpu(bg->bg_block_bitmap_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (ext4_fsblk_t)le32_to_cpu(bg->bg_block_bitmap_hi) << 32 : 0);
}

ext4_fsblk_t ext4_inode_bitmap(struct super_block *sb,
                               struct ext4_group_desc *bg)
{
        return le32_to_cpu(bg->bg_inode_bitmap_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (ext4_fsblk_t)le32_to_cpu(bg->bg_inode_bitmap_hi) << 32 : 0);
}

ext4_fsblk_t ext4_inode_table(struct super_block *sb,
                              struct ext4_group_desc *bg)
{
        return le32_to_cpu(bg->bg_inode_table_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (ext4_fsblk_t)le32_to_cpu(bg->bg_inode_table_hi) << 32 : 0);
}

__u32 ext4_free_blks_count(struct super_block *sb,
                              struct ext4_group_desc *bg)
{
        return le16_to_cpu(bg->bg_free_blocks_count_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (__u32)le16_to_cpu(bg->bg_free_blocks_count_hi) << 16 : 0);
}

__u32 ext4_free_inodes_count(struct super_block *sb,
                              struct ext4_group_desc *bg)
{
        return le16_to_cpu(bg->bg_free_inodes_count_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (__u32)le16_to_cpu(bg->bg_free_inodes_count_hi) << 16 : 0);
}

__u32 ext4_used_dirs_count(struct super_block *sb,
                              struct ext4_group_desc *bg)
{
        return le16_to_cpu(bg->bg_used_dirs_count_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (__u32)le16_to_cpu(bg->bg_used_dirs_count_hi) << 16 : 0);
}

__u32 ext4_itable_unused_count(struct super_block *sb,
                              struct ext4_group_desc *bg)
{
        return le16_to_cpu(bg->bg_itable_unused_lo) |
                (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
                 (__u32)le16_to_cpu(bg->bg_itable_unused_hi) << 16 : 0);
}

void ext4_block_bitmap_set(struct super_block *sb,
                           struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
        bg->bg_block_bitmap_lo = cpu_to_le32((u32)blk);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_block_bitmap_hi = cpu_to_le32(blk >> 32);
}

void ext4_inode_bitmap_set(struct super_block *sb,
                           struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
        bg->bg_inode_bitmap_lo  = cpu_to_le32((u32)blk);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_inode_bitmap_hi = cpu_to_le32(blk >> 32);
}

void ext4_inode_table_set(struct super_block *sb,
                          struct ext4_group_desc *bg, ext4_fsblk_t blk)
{
        bg->bg_inode_table_lo = cpu_to_le32((u32)blk);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_inode_table_hi = cpu_to_le32(blk >> 32);
}

void ext4_free_blks_set(struct super_block *sb,
                          struct ext4_group_desc *bg, __u32 count)
{
        bg->bg_free_blocks_count_lo = cpu_to_le16((__u16)count);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_free_blocks_count_hi = cpu_to_le16(count >> 16);
}

void ext4_free_inodes_set(struct super_block *sb,
                          struct ext4_group_desc *bg, __u32 count)
{
        bg->bg_free_inodes_count_lo = cpu_to_le16((__u16)count);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_free_inodes_count_hi = cpu_to_le16(count >> 16);
}

void ext4_used_dirs_set(struct super_block *sb,
                          struct ext4_group_desc *bg, __u32 count)
{
        bg->bg_used_dirs_count_lo = cpu_to_le16((__u16)count);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_used_dirs_count_hi = cpu_to_le16(count >> 16);
}

void ext4_itable_unused_set(struct super_block *sb,
                          struct ext4_group_desc *bg, __u32 count)
{
        bg->bg_itable_unused_lo = cpu_to_le16((__u16)count);
        if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
                bg->bg_itable_unused_hi = cpu_to_le16(count >> 16);
}

/*
 * Wrappers for jbd2_journal_start/end.
 *
 * The only special thing we need to do here is to make sure that all
 * journal_end calls result in the superblock being marked dirty, so
 * that sync() will call the filesystem's write_super callback if
 * appropriate.
 */
handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)
{
        journal_t *journal;

        if (sb->s_flags & MS_RDONLY)
                return ERR_PTR(-EROFS);

        /* Special case here: if the journal has aborted behind our
         * backs (eg. EIO in the commit thread), then we still need to
         * take the FS itself readonly cleanly. */
        journal = EXT4_SB(sb)->s_journal;
        if (journal) {
                if (is_journal_aborted(journal)) {
                        ext4_abort(sb, __func__, "Detected aborted journal");
                        return ERR_PTR(-EROFS);
                }
                return jbd2_journal_start(journal, nblocks);
        }
        /*
         * We're not journaling, return the appropriate indication.
         */
        current->journal_info = EXT4_NOJOURNAL_HANDLE;
        return current->journal_info;
}

/*
 * The only special thing we need to do here is to make sure that all
 * jbd2_journal_stop calls result in the superblock being marked dirty, so
 * that sync() will call the filesystem's write_super callback if
 * appropriate.
 */
int __ext4_journal_stop(const char *where, handle_t *handle)
{
        struct super_block *sb;
        int err;
        int rc;

        if (!ext4_handle_valid(handle)) {
                /*
                 * Do this here since we don't call jbd2_journal_stop() in
                 * no-journal mode.
                 */
                current->journal_info = NULL;
                return 0;
        }
        sb = handle->h_transaction->t_journal->j_private;
        err = handle->h_err;
        rc = jbd2_journal_stop(handle);

        if (!err)
                err = rc;
        if (err)
                __ext4_std_error(sb, where, err);
        return err;
}

void ext4_journal_abort_handle(const char *caller, const char *err_fn,
                struct buffer_head *bh, handle_t *handle, int err)
{
        char nbuf[16];
        const char *errstr = ext4_decode_error(NULL, err, nbuf);

        BUG_ON(!ext4_handle_valid(handle));

        if (bh)
                BUFFER_TRACE(bh, "abort");

        if (!handle->h_err)
                handle->h_err = err;

        if (is_handle_aborted(handle))
                return;

        printk(KERN_ERR "%s: aborting transaction: %s in %s\n",
               caller, errstr, err_fn);

        jbd2_journal_abort_handle(handle);
}

/* Deal with the reporting of failure conditions on a filesystem such as
 * inconsistencies detected or read IO failures.
 *
 * On ext2, we can store the error state of the filesystem in the
 * superblock.  That is not possible on ext4, because we may have other
 * write ordering constraints on the superblock which prevent us from
 * writing it out straight away; and given that the journal is about to
 * be aborted, we can't rely on the current, or future, transactions to
 * write out the superblock safely.
 *
 * We'll just use the jbd2_journal_abort() error code to record an error in
 * the journal instead.  On recovery, the journal will compain about
 * that error until we've noted it down and cleared it.
 */

static void ext4_handle_error(struct super_block *sb)
{
        struct ext4_super_block *es = EXT4_SB(sb)->s_es;

        EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
        es->s_state |= cpu_to_le16(EXT4_ERROR_FS);

        if (sb->s_flags & MS_RDONLY)
                return;

        if (!test_opt(sb, ERRORS_CONT)) {
                journal_t *journal = EXT4_SB(sb)->s_journal;

                EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;
                if (journal)
                        jbd2_journal_abort(journal, -EIO);
        }
        if (test_opt(sb, ERRORS_RO)) {
                ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
                sb->s_flags |= MS_RDONLY;
        }
        ext4_commit_super(sb, 1);
        if (test_opt(sb, ERRORS_PANIC))
                panic("EXT4-fs (device %s): panic forced after error\n",
                        sb->s_id);
}

void ext4_error(struct super_block *sb, const char *function,
                const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk(KERN_CRIT "EXT4-fs error (device %s): %s: ", sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);

        ext4_handle_error(sb);
}

static const char *ext4_decode_error(struct super_block *sb, int errno,
                                     char nbuf[16])
{
        char *errstr = NULL;

        switch (errno) {
        case -EIO:
                errstr = "IO failure";
                break;
        case -ENOMEM:
                errstr = "Out of memory";
                break;
        case -EROFS:
                if (!sb || (EXT4_SB(sb)->s_journal &&
                            EXT4_SB(sb)->s_journal->j_flags & JBD2_ABORT))
                        errstr = "Journal has aborted";
                else
                        errstr = "Readonly filesystem";
                break;
        default:
                /* If the caller passed in an extra buffer for unknown
                 * errors, textualise them now.  Else we just return
                 * NULL. */
                if (nbuf) {
                        /* Check for truncated error codes... */
                        if (snprintf(nbuf, 16, "error %d", -errno) >= 0)
                                errstr = nbuf;
                }
                break;
        }

        return errstr;
}

/* __ext4_std_error decodes expected errors from journaling functions
 * automatically and invokes the appropriate error response.  */

void __ext4_std_error(struct super_block *sb, const char *function, int errno)
{
        char nbuf[16];
        const char *errstr;

        /* Special case: if the error is EROFS, and we're not already
         * inside a transaction, then there's really no point in logging
         * an error. */
        if (errno == -EROFS && journal_current_handle() == NULL &&
            (sb->s_flags & MS_RDONLY))
                return;

        errstr = ext4_decode_error(sb, errno, nbuf);
        printk(KERN_CRIT "EXT4-fs error (device %s) in %s: %s\n",
               sb->s_id, function, errstr);

        ext4_handle_error(sb);
}

/*
 * ext4_abort is a much stronger failure handler than ext4_error.  The
 * abort function may be used to deal with unrecoverable failures such
 * as journal IO errors or ENOMEM at a critical moment in log management.
 *
 * We unconditionally force the filesystem into an ABORT|READONLY state,
 * unless the error response on the fs has been set to panic in which
 * case we take the easy way out and panic immediately.
 */

void ext4_abort(struct super_block *sb, const char *function,
                const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk(KERN_CRIT "EXT4-fs error (device %s): %s: ", sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);

        if (test_opt(sb, ERRORS_PANIC))
                panic("EXT4-fs panic from previous error\n");

        if (sb->s_flags & MS_RDONLY)
                return;

        ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
        EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
        sb->s_flags |= MS_RDONLY;
        EXT4_SB(sb)->s_mount_flags |= EXT4_MF_FS_ABORTED;
        if (EXT4_SB(sb)->s_journal)
                jbd2_journal_abort(EXT4_SB(sb)->s_journal, -EIO);
}

void ext4_msg (struct super_block * sb, const char *prefix,
                   const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk("%sEXT4-fs (%s): ", prefix, sb->s_id);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);
}

void ext4_warning(struct super_block *sb, const char *function,
                  const char *fmt, ...)
{
        va_list args;

        va_start(args, fmt);
        printk(KERN_WARNING "EXT4-fs warning (device %s): %s: ",
               sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);
}

void ext4_grp_locked_error(struct super_block *sb, ext4_group_t grp,
                           const char *function, const char *fmt, ...)
__releases(bitlock)
__acquires(bitlock)
{
        va_list args;
        struct ext4_super_block *es = EXT4_SB(sb)->s_es;

        va_start(args, fmt);
        printk(KERN_CRIT "EXT4-fs error (device %s): %s: ", sb->s_id, function);
        vprintk(fmt, args);
        printk("\n");
        va_end(args);

        if (test_opt(sb, ERRORS_CONT)) {
                EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
                es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
                ext4_commit_super(sb, 0);
                return;
        }
        ext4_unlock_group(sb, grp);
        ext4_handle_error(sb);
        /*
         * We only get here in the ERRORS_RO case; relocking the group
         * may be dangerous, but nothing bad will happen since the
         * filesystem will have already been marked read/only and the
         * journal has been aborted.  We return 1 as a hint to callers
         * who might what to use the return value from
         * ext4_grp_locked_error() to distinguish beween the
         * ERRORS_CONT and ERRORS_RO case, and perhaps return more
         * aggressively from the ext4 function in question, with a
         * more appropriate error code.
         */
        ext4_lock_group(sb, grp);
        return;
}

void ext4_update_dynamic_rev(struct super_block *sb)
{
        struct ext4_super_block *es = EXT4_SB(sb)->s_es;

        if (le32_to_cpu(es->s_rev_level) > EXT4_GOOD_OLD_REV)
                return;

        ext4_warning(sb, __func__,
                     "updating to rev %d because of new feature flag, "
                     "running e2fsck is recommended",
                     EXT4_DYNAMIC_REV);

        es->s_first_ino = cpu_to_le32(EXT4_GOOD_OLD_FIRST_INO);
        es->s_inode_size = cpu_to_le16(EXT4_GOOD_OLD_INODE_SIZE);
        es->s_rev_level = cpu_to_le32(EXT4_DYNAMIC_REV);
        /* leave es->s_feature_*compat flags alone */
        /* es->s_uuid will be set by e2fsck if empty */

        /*
         * The rest of the superblock fields should be zero, and if not it
         * means they are likely already in use, so leave them alone.  We
         * can leave it up to e2fsck to clean up any inconsistencies there.
         */
}

/*
 * Open the external journal device
 */
static struct block_device *ext4_blkdev_get(dev_t dev, struct super_block *sb)
{
        struct block_device *bdev;
        char b[BDEVNAME_SIZE];

        bdev = open_by_devnum(dev, FMODE_READ|FMODE_WRITE);
        if (IS_ERR(bdev))
                goto fail;
        return bdev;

fail:
        ext4_msg(sb, KERN_ERR, "failed to open journal device %s: %ld",
                        __bdevname(dev, b), PTR_ERR(bdev));
        return NULL;
}

/*
 * Release the journal device
 */
static int ext4_blkdev_put(struct block_device *bdev)
{
        bd_release(bdev);
        return blkdev_put(bdev, FMODE_READ|FMODE_WRITE);
}

static int ext4_blkdev_remove(struct ext4_sb_info *sbi)
{
        struct block_device *bdev;
        int ret = -ENODEV;

        bdev = sbi->journal_bdev;
        if (bdev) {
                ret = ext4_blkdev_put(bdev);
                sbi->journal_bdev = NULL;
        }
        return ret;
}

static inline struct inode *orphan_list_entry(struct list_head *l)
{
        return &list_entry(l, struct ext4_inode_info, i_orphan)->vfs_inode;
}

static void dump_orphan_list(struct super_block *sb, struct ext4_sb_info *sbi)
{
        struct list_head *l;

        ext4_msg(sb, KERN_ERR, "sb orphan head is %d",
                 le32_to_cpu(sbi->s_es->s_last_orphan));

        printk(KERN_ERR "sb_info orphan list:\n");
        list_for_each(l, &sbi->s_orphan) {
                struct inode *inode = orphan_list_entry(l);
                printk(KERN_ERR "  "
                       "inode %s:%lu at %p: mode %o, nlink %d, next %d\n",
                       inode->i_sb->s_id, inode->i_ino, inode,
                       inode->i_mode, inode->i_nlink,
                       NEXT_ORPHAN(inode));
        }
}

static void ext4_put_super(struct super_block *sb)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct ext4_super_block *es = sbi->s_es;
        int i, err;

        lock_super(sb);
        lock_kernel();
        if (sb->s_dirt)
                ext4_commit_super(sb, 1);

        ext4_release_system_zone(sb);
        ext4_mb_release(sb);
        ext4_ext_release(sb);
        ext4_xattr_put_super(sb);
        if (sbi->s_journal) {
                err = jbd2_journal_destroy(sbi->s_journal);
                sbi->s_journal = NULL;
                if (err < 0)
                        ext4_abort(sb, __func__,
                                   "Couldn't clean up the journal");
        }
        if (!(sb->s_flags & MS_RDONLY)) {
                EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
                es->s_state = cpu_to_le16(sbi->s_mount_state);
                ext4_commit_super(sb, 1);
        }
        if (sbi->s_proc) {
                remove_proc_entry(sb->s_id, ext4_proc_root);
        }
        kobject_del(&sbi->s_kobj);

        for (i = 0; i < sbi->s_gdb_count; i++)
                brelse(sbi->s_group_desc[i]);
        kfree(sbi->s_group_desc);
        if (is_vmalloc_addr(sbi->s_flex_groups))
                vfree(sbi->s_flex_groups);
        else
                kfree(sbi->s_flex_groups);
        percpu_counter_destroy(&sbi->s_freeblocks_counter);
        percpu_counter_destroy(&sbi->s_freeinodes_counter);
        percpu_counter_destroy(&sbi->s_dirs_counter);
        percpu_counter_destroy(&sbi->s_dirtyblocks_counter);
        brelse(sbi->s_sbh);
#ifdef CONFIG_QUOTA
        for (i = 0; i < MAXQUOTAS; i++)
                kfree(sbi->s_qf_names[i]);
#endif

        /* Debugging code just in case the in-memory inode orphan list
         * isn't empty.  The on-disk one can be non-empty if we've
         * detected an error and taken the fs readonly, but the
         * in-memory list had better be clean by this point. */
        if (!list_empty(&sbi->s_orphan))
                dump_orphan_list(sb, sbi);
        J_ASSERT(list_empty(&sbi->s_orphan));

        invalidate_bdev(sb->s_bdev);
        if (sbi->journal_bdev && sbi->journal_bdev != sb->s_bdev) {
                /*
                 * Invalidate the journal device's buffers.  We don't want them
                 * floating about in memory - the physical journal device may
                 * hotswapped, and it breaks the `ro-after' testing code.
                 */
                sync_blockdev(sbi->journal_bdev);
                invalidate_bdev(sbi->journal_bdev);
                ext4_blkdev_remove(sbi);
        }
        sb->s_fs_info = NULL;
        /*
         * Now that we are completely done shutting down the
         * superblock, we need to actually destroy the kobject.
         */
        unlock_kernel();
        unlock_super(sb);
        kobject_put(&sbi->s_kobj);
        wait_for_completion(&sbi->s_kobj_unregister);
        kfree(sbi->s_blockgroup_lock);
        kfree(sbi);
}

static struct kmem_cache *ext4_inode_cachep;

/*
 * Called inside transaction, so use GFP_NOFS
 */
static struct inode *ext4_alloc_inode(struct super_block *sb)
{
        struct ext4_inode_info *ei;

        ei = kmem_cache_alloc(ext4_inode_cachep, GFP_NOFS);
        if (!ei)
                return NULL;

        ei->vfs_inode.i_version = 1;
        ei->vfs_inode.i_data.writeback_index = 0;
        memset(&ei->i_cached_extent, 0, sizeof(struct ext4_ext_cache));
        INIT_LIST_HEAD(&ei->i_prealloc_list);
        spin_lock_init(&ei->i_prealloc_lock);
        /*
         * Note:  We can be called before EXT4_SB(sb)->s_journal is set,
         * therefore it can be null here.  Don't check it, just initialize
         * jinode.
         */
        jbd2_journal_init_jbd_inode(&ei->jinode, &ei->vfs_inode);
        ei->i_reserved_data_blocks = 0;
        ei->i_reserved_meta_blocks = 0;
        ei->i_allocated_meta_blocks = 0;
        ei->i_delalloc_reserved_flag = 0;
        spin_lock_init(&(ei->i_block_reservation_lock));

        return &ei->vfs_inode;
}

static void ext4_destroy_inode(struct inode *inode)
{
        if (!list_empty(&(EXT4_I(inode)->i_orphan))) {
                ext4_msg(inode->i_sb, KERN_ERR,
                         "Inode %lu (%p): orphan list check failed!",
                         inode->i_ino, EXT4_I(inode));
                print_hex_dump(KERN_INFO, "", DUMP_PREFIX_ADDRESS, 16, 4,
                                EXT4_I(inode), sizeof(struct ext4_inode_info),
                                true);
                dump_stack();
        }
        kmem_cache_free(ext4_inode_cachep, EXT4_I(inode));
}

static void init_once(void *foo)
{
        struct ext4_inode_info *ei = (struct ext4_inode_info *) foo;

        INIT_LIST_HEAD(&ei->i_orphan);
#ifdef CONFIG_EXT4_FS_XATTR
        init_rwsem(&ei->xattr_sem);
#endif
        init_rwsem(&ei->i_data_sem);
        inode_init_once(&ei->vfs_inode);
}

static int init_inodecache(void)
{
        ext4_inode_cachep = kmem_cache_create("ext4_inode_cache",
                                             sizeof(struct ext4_inode_info),
                                             0, (SLAB_RECLAIM_ACCOUNT|
                                                SLAB_MEM_SPREAD),
                                             init_once);
        if (ext4_inode_cachep == NULL)
                return -ENOMEM;
        return 0;
}

static void destroy_inodecache(void)
{
        kmem_cache_destroy(ext4_inode_cachep);
}

static void ext4_clear_inode(struct inode *inode)
{
        ext4_discard_preallocations(inode);
        if (EXT4_JOURNAL(inode))
                jbd2_journal_release_jbd_inode(EXT4_SB(inode->i_sb)->s_journal,
                                       &EXT4_I(inode)->jinode);
}

static inline void ext4_show_quota_options(struct seq_file *seq,
                                           struct super_block *sb)
{
#if defined(CONFIG_QUOTA)
        struct ext4_sb_info *sbi = EXT4_SB(sb);

        if (sbi->s_jquota_fmt)
                seq_printf(seq, ",jqfmt=%s",
                (sbi->s_jquota_fmt == QFMT_VFS_OLD) ? "vfsold" : "vfsv0");

        if (sbi->s_qf_names[USRQUOTA])
                seq_printf(seq, ",usrjquota=%s", sbi->s_qf_names[USRQUOTA]);

        if (sbi->s_qf_names[GRPQUOTA])
                seq_printf(seq, ",grpjquota=%s", sbi->s_qf_names[GRPQUOTA]);

        if (sbi->s_mount_opt & EXT4_MOUNT_USRQUOTA)
                seq_puts(seq, ",usrquota");

        if (sbi->s_mount_opt & EXT4_MOUNT_GRPQUOTA)
                seq_puts(seq, ",grpquota");
#endif
}

/*
 * Show an option if
 *  - it's set to a non-default value OR
 *  - if the per-sb default is different from the global default
 */
static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
        int def_errors;
        unsigned long def_mount_opts;
        struct super_block *sb = vfs->mnt_sb;
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct ext4_super_block *es = sbi->s_es;

        def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
        def_errors     = le16_to_cpu(es->s_errors);

        if (sbi->s_sb_block != 1)
                seq_printf(seq, ",sb=%llu", sbi->s_sb_block);
        if (test_opt(sb, MINIX_DF))
                seq_puts(seq, ",minixdf");
        if (test_opt(sb, GRPID) && !(def_mount_opts & EXT4_DEFM_BSDGROUPS))
                seq_puts(seq, ",grpid");
        if (!test_opt(sb, GRPID) && (def_mount_opts & EXT4_DEFM_BSDGROUPS))
                seq_puts(seq, ",nogrpid");
        if (sbi->s_resuid != EXT4_DEF_RESUID ||
            le16_to_cpu(es->s_def_resuid) != EXT4_DEF_RESUID) {
                seq_printf(seq, ",resuid=%u", sbi->s_resuid);
        }
        if (sbi->s_resgid != EXT4_DEF_RESGID ||
            le16_to_cpu(es->s_def_resgid) != EXT4_DEF_RESGID) {
                seq_printf(seq, ",resgid=%u", sbi->s_resgid);
        }
        if (test_opt(sb, ERRORS_RO)) {
                if (def_errors == EXT4_ERRORS_PANIC ||
                    def_errors == EXT4_ERRORS_CONTINUE) {
                        seq_puts(seq, ",errors=remount-ro");
                }
        }
        if (test_opt(sb, ERRORS_CONT) && def_errors != EXT4_ERRORS_CONTINUE)
                seq_puts(seq, ",errors=continue");
        if (test_opt(sb, ERRORS_PANIC) && def_errors != EXT4_ERRORS_PANIC)
                seq_puts(seq, ",errors=panic");
        if (test_opt(sb, NO_UID32) && !(def_mount_opts & EXT4_DEFM_UID16))
                seq_puts(seq, ",nouid32");
        if (test_opt(sb, DEBUG) && !(def_mount_opts & EXT4_DEFM_DEBUG))
                seq_puts(seq, ",debug");
        if (test_opt(sb, OLDALLOC))
                seq_puts(seq, ",oldalloc");
#ifdef CONFIG_EXT4_FS_XATTR
        if (test_opt(sb, XATTR_USER) &&
                !(def_mount_opts & EXT4_DEFM_XATTR_USER))
                seq_puts(seq, ",user_xattr");
        if (!test_opt(sb, XATTR_USER) &&
            (def_mount_opts & EXT4_DEFM_XATTR_USER)) {
                seq_puts(seq, ",nouser_xattr");
        }
#endif
#ifdef CONFIG_EXT4_FS_POSIX_ACL
        if (test_opt(sb, POSIX_ACL) && !(def_mount_opts & EXT4_DEFM_ACL))
                seq_puts(seq, ",acl");
        if (!test_opt(sb, POSIX_ACL) && (def_mount_opts & EXT4_DEFM_ACL))
                seq_puts(seq, ",noacl");
#endif
        if (sbi->s_commit_interval != JBD2_DEFAULT_MAX_COMMIT_AGE*HZ) {
                seq_printf(seq, ",commit=%u",
                           (unsigned) (sbi->s_commit_interval / HZ));
        }
        if (sbi->s_min_batch_time != EXT4_DEF_MIN_BATCH_TIME) {
                seq_printf(seq, ",min_batch_time=%u",
                           (unsigned) sbi->s_min_batch_time);
        }
        if (sbi->s_max_batch_time != EXT4_DEF_MAX_BATCH_TIME) {
                seq_printf(seq, ",max_batch_time=%u",
                           (unsigned) sbi->s_min_batch_time);
        }

        /*
         * We're changing the default of barrier mount option, so
         * let's always display its mount state so it's clear what its
         * status is.
         */
        seq_puts(seq, ",barrier=");
        seq_puts(seq, test_opt(sb, BARRIER) ? "1" : "0");
        if (test_opt(sb, JOURNAL_ASYNC_COMMIT))
                seq_puts(seq, ",journal_async_commit");
        if (test_opt(sb, NOBH))
                seq_puts(seq, ",nobh");
        if (test_opt(sb, I_VERSION))
                seq_puts(seq, ",i_version");
        if (!test_opt(sb, DELALLOC))
                seq_puts(seq, ",nodelalloc");


        if (sbi->s_stripe)
                seq_printf(seq, ",stripe=%lu", sbi->s_stripe);
        /*
         * journal mode get enabled in different ways
         * So just print the value even if we didn't specify it
         */
        if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
                seq_puts(seq, ",data=journal");
        else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA)
                seq_puts(seq, ",data=ordered");
        else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA)
                seq_puts(seq, ",data=writeback");

        if (sbi->s_inode_readahead_blks != EXT4_DEF_INODE_READAHEAD_BLKS)
                seq_printf(seq, ",inode_readahead_blks=%u",
                           sbi->s_inode_readahead_blks);

        if (test_opt(sb, DATA_ERR_ABORT))
                seq_puts(seq, ",data_err=abort");

        if (test_opt(sb, NO_AUTO_DA_ALLOC))
                seq_puts(seq, ",noauto_da_alloc");

        ext4_show_quota_options(seq, sb);

        return 0;
}

static struct inode *ext4_nfs_get_inode(struct super_block *sb,
                                        u64 ino, u32 generation)
{
        struct inode *inode;

        if (ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO)
                return ERR_PTR(-ESTALE);
        if (ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count))
                return ERR_PTR(-ESTALE);

        /* iget isn't really right if the inode is currently unallocated!!
         *
         * ext4_read_inode will return a bad_inode if the inode had been
         * deleted, so we should be safe.
         *
         * Currently we don't know the generation for parent directory, so
         * a generation of 0 means "accept any"
         */
        inode = ext4_iget(sb, ino);
        if (IS_ERR(inode))
                return ERR_CAST(inode);
        if (generation && inode->i_generation != generation) {
                iput(inode);
                return ERR_PTR(-ESTALE);
        }

        return inode;
}

static struct dentry *ext4_fh_to_dentry(struct super_block *sb, struct fid *fid,
                                        int fh_len, int fh_type)
{
        return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
                                    ext4_nfs_get_inode);
}

static struct dentry *ext4_fh_to_parent(struct super_block *sb, struct fid *fid,
                                        int fh_len, int fh_type)
{
        return generic_fh_to_parent(sb, fid, fh_len, fh_type,
                                    ext4_nfs_get_inode);
}

/*
 * Try to release metadata pages (indirect blocks, directories) which are
 * mapped via the block device.  Since these pages could have journal heads
 * which would prevent try_to_free_buffers() from freeing them, we must use
 * jbd2 layer's try_to_free_buffers() function to release them.
 */
static int bdev_try_to_free_page(struct super_block *sb, struct page *page,
                                 gfp_t wait)
{
        journal_t *journal = EXT4_SB(sb)->s_journal;

        WARN_ON(PageChecked(page));
        if (!page_has_buffers(page))
                return 0;
        if (journal)
                return jbd2_journal_try_to_free_buffers(journal, page,
                                                        wait & ~__GFP_WAIT);
        return try_to_free_buffers(page);
}

#ifdef CONFIG_QUOTA
#define QTYPE2NAME(t) ((t) == USRQUOTA ? "user" : "group")
#define QTYPE2MOPT(on, t) ((t) == USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))

static int ext4_write_dquot(struct dquot *dquot);
static int ext4_acquire_dquot(struct dquot *dquot);
static int ext4_release_dquot(struct dquot *dquot);
static int ext4_mark_dquot_dirty(struct dquot *dquot);
static int ext4_write_info(struct super_block *sb, int type);
static int ext4_quota_on(struct super_block *sb, int type, int format_id,
                                char *path, int remount);
static int ext4_quota_on_mount(struct super_block *sb, int type);
static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data,
                               size_t len, loff_t off);
static ssize_t ext4_quota_write(struct super_block *sb, int type,
                                const char *data, size_t len, loff_t off);

static struct dquot_operations ext4_quota_operations = {
        .initialize     = dquot_initialize,
        .drop           = dquot_drop,
        .alloc_space    = dquot_alloc_space,
        .reserve_space  = dquot_reserve_space,
        .claim_space    = dquot_claim_space,
        .release_rsv    = dquot_release_reserved_space,
        .get_reserved_space = ext4_get_reserved_space,
        .alloc_inode    = dquot_alloc_inode,
        .free_space     = dquot_free_space,
        .free_inode     = dquot_free_inode,
        .transfer       = dquot_transfer,
        .write_dquot    = ext4_write_dquot,
        .acquire_dquot  = ext4_acquire_dquot,
        .release_dquot  = ext4_release_dquot,
        .mark_dirty     = ext4_mark_dquot_dirty,
        .write_info     = ext4_write_info,
        .alloc_dquot    = dquot_alloc,
        .destroy_dquot  = dquot_destroy,
};

static struct quotactl_ops ext4_qctl_operations = {
        .quota_on       = ext4_quota_on,
        .quota_off      = vfs_quota_off,
        .quota_sync     = vfs_quota_sync,
        .get_info       = vfs_get_dqinfo,
        .set_info       = vfs_set_dqinfo,
        .get_dqblk      = vfs_get_dqblk,
        .set_dqblk      = vfs_set_dqblk
};
#endif

static const struct super_operations ext4_sops = {
        .alloc_inode    = ext4_alloc_inode,
        .destroy_inode  = ext4_destroy_inode,
        .write_inode    = ext4_write_inode,
        .dirty_inode    = ext4_dirty_inode,
        .delete_inode   = ext4_delete_inode,
        .put_super      = ext4_put_super,
        .sync_fs        = ext4_sync_fs,
        .freeze_fs      = ext4_freeze,
        .unfreeze_fs    = ext4_unfreeze,
        .statfs         = ext4_statfs,
        .remount_fs     = ext4_remount,
        .clear_inode    = ext4_clear_inode,
        .show_options   = ext4_show_options,
#ifdef CONFIG_QUOTA
        .quota_read     = ext4_quota_read,
        .quota_write    = ext4_quota_write,
#endif
        .bdev_try_to_free_page = bdev_try_to_free_page,
};

static const struct super_operations ext4_nojournal_sops = {
        .alloc_inode    = ext4_alloc_inode,
        .destroy_inode  = ext4_destroy_inode,
        .write_inode    = ext4_write_inode,
        .dirty_inode    = ext4_dirty_inode,
        .delete_inode   = ext4_delete_inode,
        .write_super    = ext4_write_super,
        .put_super      = ext4_put_super,
        .statfs         = ext4_statfs,
        .remount_fs     = ext4_remount,
        .clear_inode    = ext4_clear_inode,
        .show_options   = ext4_show_options,
#ifdef CONFIG_QUOTA
        .quota_read     = ext4_quota_read,
        .quota_write    = ext4_quota_write,
#endif
        .bdev_try_to_free_page = bdev_try_to_free_page,
};

static const struct export_operations ext4_export_ops = {
        .fh_to_dentry = ext4_fh_to_dentry,
        .fh_to_parent = ext4_fh_to_parent,
        .get_parent = ext4_get_parent,
};

enum {
        Opt_bsd_df, Opt_minix_df, Opt_grpid, Opt_nogrpid,
        Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,
        Opt_nouid32, Opt_debug, Opt_oldalloc, Opt_orlov,
        Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,
        Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload, Opt_nobh, Opt_bh,
        Opt_commit, Opt_min_batch_time, Opt_max_batch_time,
        Opt_journal_update, Opt_journal_dev,
        Opt_journal_checksum, Opt_journal_async_commit,
        Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
        Opt_data_err_abort, Opt_data_err_ignore, Opt_mb_history_length,
        Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
        Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
        Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,
        Opt_usrquota, Opt_grpquota, Opt_i_version,
        Opt_stripe, Opt_delalloc, Opt_nodelalloc,
        Opt_block_validity, Opt_noblock_validity,
        Opt_inode_readahead_blks, Opt_journal_ioprio
};

static const match_table_t tokens = {
        {Opt_bsd_df, "bsddf"},
        {Opt_minix_df, "minixdf"},
        {Opt_grpid, "grpid"},
        {Opt_grpid, "bsdgroups"},
        {Opt_nogrpid, "nogrpid"},
        {Opt_nogrpid, "sysvgroups"},
        {Opt_resgid, "resgid=%u"},
        {Opt_resuid, "resuid=%u"},
        {Opt_sb, "sb=%u"},
        {Opt_err_cont, "errors=continue"},
        {Opt_err_panic, "errors=panic"},
        {Opt_err_ro, "errors=remount-ro"},
        {Opt_nouid32, "nouid32"},
        {Opt_debug, "debug"},
        {Opt_oldalloc, "oldalloc"},
        {Opt_orlov, "orlov"},
        {Opt_user_xattr, "user_xattr"},
        {Opt_nouser_xattr, "nouser_xattr"},
        {Opt_acl, "acl"},
        {Opt_noacl, "noacl"},
        {Opt_noload, "noload"},
        {Opt_nobh, "nobh"},
        {Opt_bh, "bh"},
        {Opt_commit, "commit=%u"},
        {Opt_min_batch_time, "min_batch_time=%u"},
        {Opt_max_batch_time, "max_batch_time=%u"},
        {Opt_journal_update, "journal=update"},
        {Opt_journal_dev, "journal_dev=%u"},
        {Opt_journal_checksum, "journal_checksum"},
        {Opt_journal_async_commit, "journal_async_commit"},
        {Opt_abort, "abort"},
        {Opt_data_journal, "data=journal"},
        {Opt_data_ordered, "data=ordered"},
        {Opt_data_writeback, "data=writeback"},
        {Opt_data_err_abort, "data_err=abort"},
        {Opt_data_err_ignore, "data_err=ignore"},
        {Opt_mb_history_length, "mb_history_length=%u"},
        {Opt_offusrjquota, "usrjquota="},
        {Opt_usrjquota, "usrjquota=%s"},
        {Opt_offgrpjquota, "grpjquota="},
        {Opt_grpjquota, "grpjquota=%s"},
        {Opt_jqfmt_vfsold, "jqfmt=vfsold"},
        {Opt_jqfmt_vfsv0, "jqfmt=vfsv0"},
        {Opt_grpquota, "grpquota"},
        {Opt_noquota, "noquota"},
        {Opt_quota, "quota"},
        {Opt_usrquota, "usrquota"},
        {Opt_barrier, "barrier=%u"},
        {Opt_barrier, "barrier"},
        {Opt_nobarrier, "nobarrier"},
        {Opt_i_version, "i_version"},
        {Opt_stripe, "stripe=%u"},
        {Opt_resize, "resize"},
        {Opt_delalloc, "delalloc"},
        {Opt_nodelalloc, "nodelalloc"},
        {Opt_block_validity, "block_validity"},
        {Opt_noblock_validity, "noblock_validity"},
        {Opt_inode_readahead_blks, "inode_readahead_blks=%u"},
        {Opt_journal_ioprio, "journal_ioprio=%u"},
        {Opt_auto_da_alloc, "auto_da_alloc=%u"},
        {Opt_auto_da_alloc, "auto_da_alloc"},
        {Opt_noauto_da_alloc, "noauto_da_alloc"},
        {Opt_err, NULL},
};

static ext4_fsblk_t get_sb_block(void **data)
{
        ext4_fsblk_t    sb_block;
        char            *options = (char *) *data;

        if (!options || strncmp(options, "sb=", 3) != 0)
                return 1;       /* Default location */

        options += 3;
        /* TODO: use simple_strtoll with >32bit ext4 */
        sb_block = simple_strtoul(options, &options, 0);
        if (*options && *options != ',') {
                printk(KERN_ERR "EXT4-fs: Invalid sb specification: %s\n",
                       (char *) *data);
                return 1;
        }
        if (*options == ',')
                options++;
        *data = (void *) options;

        return sb_block;
}

#define DEFAULT_JOURNAL_IOPRIO (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, 3))

static int parse_options(char *options, struct super_block *sb,
                         unsigned long *journal_devnum,
                         unsigned int *journal_ioprio,
                         ext4_fsblk_t *n_blocks_count, int is_remount)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        char *p;
        substring_t args[MAX_OPT_ARGS];
        int data_opt = 0;
        int option;
#ifdef CONFIG_QUOTA
        int qtype, qfmt;
        char *qname;
#endif

        if (!options)
                return 1;

        while ((p = strsep(&options, ",")) != NULL) {
                int token;
                if (!*p)
                        continue;

                token = match_token(p, tokens, args);
                switch (token) {
                case Opt_bsd_df:
                        clear_opt(sbi->s_mount_opt, MINIX_DF);
                        break;
                case Opt_minix_df:
                        set_opt(sbi->s_mount_opt, MINIX_DF);
                        break;
                case Opt_grpid:
                        set_opt(sbi->s_mount_opt, GRPID);
                        break;
                case Opt_nogrpid:
                        clear_opt(sbi->s_mount_opt, GRPID);
                        break;
                case Opt_resuid:
                        if (match_int(&args[0], &option))
                                return 0;
                        sbi->s_resuid = option;
                        break;
                case Opt_resgid:
                        if (match_int(&args[0], &option))
                                return 0;
                        sbi->s_resgid = option;
                        break;
                case Opt_sb:
                        /* handled by get_sb_block() instead of here */
                        /* *sb_block = match_int(&args[0]); */
                        break;
                case Opt_err_panic:
                        clear_opt(sbi->s_mount_opt, ERRORS_CONT);
                        clear_opt(sbi->s_mount_opt, ERRORS_RO);
                        set_opt(sbi->s_mount_opt, ERRORS_PANIC);
                        break;
                case Opt_err_ro:
                        clear_opt(sbi->s_mount_opt, ERRORS_CONT);
                        clear_opt(sbi->s_mount_opt, ERRORS_PANIC);
                        set_opt(sbi->s_mount_opt, ERRORS_RO);
                        break;
                case Opt_err_cont:
                        clear_opt(sbi->s_mount_opt, ERRORS_RO);
                        clear_opt(sbi->s_mount_opt, ERRORS_PANIC);
                        set_opt(sbi->s_mount_opt, ERRORS_CONT);
                        break;
                case Opt_nouid32:
                        set_opt(sbi->s_mount_opt, NO_UID32);
                        break;
                case Opt_debug:
                        set_opt(sbi->s_mount_opt, DEBUG);
                        break;
                case Opt_oldalloc:
                        set_opt(sbi->s_mount_opt, OLDALLOC);
                        break;
                case Opt_orlov:
                        clear_opt(sbi->s_mount_opt, OLDALLOC);
                        break;
#ifdef CONFIG_EXT4_FS_XATTR
                case Opt_user_xattr:
                        set_opt(sbi->s_mount_opt, XATTR_USER);
                        break;
                case Opt_nouser_xattr:
                        clear_opt(sbi->s_mount_opt, XATTR_USER);
                        break;
#else
                case Opt_user_xattr:
                case Opt_nouser_xattr:
                        ext4_msg(sb, KERN_ERR, "(no)user_xattr options not supported");
                        break;
#endif
#ifdef CONFIG_EXT4_FS_POSIX_ACL
                case Opt_acl:
                        set_opt(sbi->s_mount_opt, POSIX_ACL);
                        break;
                case Opt_noacl:
                        clear_opt(sbi->s_mount_opt, POSIX_ACL);
                        break;
#else
                case Opt_acl:
                case Opt_noacl:
                        ext4_msg(sb, KERN_ERR, "(no)acl options not supported");
                        break;
#endif
                case Opt_journal_update:
                        /* @@@ FIXME */
                        /* Eventually we will want to be able to create
                           a journal file here.  For now, only allow the
                           user to specify an existing inode to be the
                           journal file. */
                        if (is_remount) {
                                ext4_msg(sb, KERN_ERR,
                                         "Cannot specify journal on remount");
                                return 0;
                        }
                        set_opt(sbi->s_mount_opt, UPDATE_JOURNAL);
                        break;
                case Opt_journal_dev:
                        if (is_remount) {
                                ext4_msg(sb, KERN_ERR,
                                        "Cannot specify journal on remount");
                                return 0;
                        }
                        if (match_int(&args[0], &option))
                                return 0;
                        *journal_devnum = option;
                        break;
                case Opt_journal_checksum:
                        set_opt(sbi->s_mount_opt, JOURNAL_CHECKSUM);
                        break;
                case Opt_journal_async_commit:
                        set_opt(sbi->s_mount_opt, JOURNAL_ASYNC_COMMIT);
                        set_opt(sbi->s_mount_opt, JOURNAL_CHECKSUM);
                        break;
                case Opt_noload:
                        set_opt(sbi->s_mount_opt, NOLOAD);
                        break;
                case Opt_commit:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0)
                                return 0;
                        if (option == 0)
                                option = JBD2_DEFAULT_MAX_COMMIT_AGE;
                        sbi->s_commit_interval = HZ * option;
                        break;
                case Opt_max_batch_time:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0)
                                return 0;
                        if (option == 0)
                                option = EXT4_DEF_MAX_BATCH_TIME;
                        sbi->s_max_batch_time = option;
                        break;
                case Opt_min_batch_time:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0)
                                return 0;
                        sbi->s_min_batch_time = option;
                        break;
                case Opt_data_journal:
                        data_opt = EXT4_MOUNT_JOURNAL_DATA;
                        goto datacheck;
                case Opt_data_ordered:
                        data_opt = EXT4_MOUNT_ORDERED_DATA;
                        goto datacheck;
                case Opt_data_writeback:
                        data_opt = EXT4_MOUNT_WRITEBACK_DATA;
                datacheck:
                        if (is_remount) {
                                if ((sbi->s_mount_opt & EXT4_MOUNT_DATA_FLAGS)
                                                != data_opt) {
                                        ext4_msg(sb, KERN_ERR,
                                                "Cannot change data mode on remount");
                                        return 0;
                                }
                        } else {
                                sbi->s_mount_opt &= ~EXT4_MOUNT_DATA_FLAGS;
                                sbi->s_mount_opt |= data_opt;
                        }
                        break;
                case Opt_data_err_abort:
                        set_opt(sbi->s_mount_opt, DATA_ERR_ABORT);
                        break;
                case Opt_data_err_ignore:
                        clear_opt(sbi->s_mount_opt, DATA_ERR_ABORT);
                        break;
                case Opt_mb_history_length:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0)
                                return 0;
                        sbi->s_mb_history_max = option;
                        break;
#ifdef CONFIG_QUOTA
                case Opt_usrjquota:
                        qtype = USRQUOTA;
                        goto set_qf_name;
                case Opt_grpjquota:
                        qtype = GRPQUOTA;
set_qf_name:
                        if (sb_any_quota_loaded(sb) &&
                            !sbi->s_qf_names[qtype]) {
                                ext4_msg(sb, KERN_ERR,
                                       "Cannot change journaled "
                                       "quota options when quota turned on");
                                return 0;
                        }
                        qname = match_strdup(&args[0]);
                        if (!qname) {
                                ext4_msg(sb, KERN_ERR,
                                        "Not enough memory for "
                                        "storing quotafile name");
                                return 0;
                        }
                        if (sbi->s_qf_names[qtype] &&
                            strcmp(sbi->s_qf_names[qtype], qname)) {
                                ext4_msg(sb, KERN_ERR,
                                        "%s quota file already "
                                        "specified", QTYPE2NAME(qtype));
                                kfree(qname);
                                return 0;
                        }
                        sbi->s_qf_names[qtype] = qname;
                        if (strchr(sbi->s_qf_names[qtype], '/')) {
                                ext4_msg(sb, KERN_ERR,
                                        "quotafile must be on "
                                        "filesystem root");
                                kfree(sbi->s_qf_names[qtype]);
                                sbi->s_qf_names[qtype] = NULL;
                                return 0;
                        }
                        set_opt(sbi->s_mount_opt, QUOTA);
                        break;
                case Opt_offusrjquota:
                        qtype = USRQUOTA;
                        goto clear_qf_name;
                case Opt_offgrpjquota:
                        qtype = GRPQUOTA;
clear_qf_name:
                        if (sb_any_quota_loaded(sb) &&
                            sbi->s_qf_names[qtype]) {
                                ext4_msg(sb, KERN_ERR, "Cannot change "
                                        "journaled quota options when "
                                        "quota turned on");
                                return 0;
                        }
                        /*
                         * The space will be released later when all options
                         * are confirmed to be correct
                         */
                        sbi->s_qf_names[qtype] = NULL;
                        break;
                case Opt_jqfmt_vfsold:
                        qfmt = QFMT_VFS_OLD;
                        goto set_qf_format;
                case Opt_jqfmt_vfsv0:
                        qfmt = QFMT_VFS_V0;
set_qf_format:
                        if (sb_any_quota_loaded(sb) &&
                            sbi->s_jquota_fmt != qfmt) {
                                ext4_msg(sb, KERN_ERR, "Cannot change "
                                        "journaled quota options when "
                                        "quota turned on");
                                return 0;
                        }
                        sbi->s_jquota_fmt = qfmt;
                        break;
                case Opt_quota:
                case Opt_usrquota:
                        set_opt(sbi->s_mount_opt, QUOTA);
                        set_opt(sbi->s_mount_opt, USRQUOTA);
                        break;
                case Opt_grpquota:
                        set_opt(sbi->s_mount_opt, QUOTA);
                        set_opt(sbi->s_mount_opt, GRPQUOTA);
                        break;
                case Opt_noquota:
                        if (sb_any_quota_loaded(sb)) {
                                ext4_msg(sb, KERN_ERR, "Cannot change quota "
                                        "options when quota turned on");
                                return 0;
                        }
                        clear_opt(sbi->s_mount_opt, QUOTA);
                        clear_opt(sbi->s_mount_opt, USRQUOTA);
                        clear_opt(sbi->s_mount_opt, GRPQUOTA);
                        break;
#else
                case Opt_quota:
                case Opt_usrquota:
                case Opt_grpquota:
                        ext4_msg(sb, KERN_ERR,
                                "quota options not supported");
                        break;
                case Opt_usrjquota:
                case Opt_grpjquota:
                case Opt_offusrjquota:
                case Opt_offgrpjquota:
                case Opt_jqfmt_vfsold:
                case Opt_jqfmt_vfsv0:
                        ext4_msg(sb, KERN_ERR,
                                "journaled quota options not supported");
                        break;
                case Opt_noquota:
                        break;
#endif
                case Opt_abort:
                        sbi->s_mount_flags |= EXT4_MF_FS_ABORTED;
                        break;
                case Opt_nobarrier:
                        clear_opt(sbi->s_mount_opt, BARRIER);
                        break;
                case Opt_barrier:
                        if (match_int(&args[0], &option)) {
                                set_opt(sbi->s_mount_opt, BARRIER);
                                break;
                        }
                        if (option)
                                set_opt(sbi->s_mount_opt, BARRIER);
                        else
                                clear_opt(sbi->s_mount_opt, BARRIER);
                        break;
                case Opt_ignore:
                        break;
                case Opt_resize:
                        if (!is_remount) {
                                ext4_msg(sb, KERN_ERR,
                                        "resize option only available "
                                        "for remount");
                                return 0;
                        }
                        if (match_int(&args[0], &option) != 0)
                                return 0;
                        *n_blocks_count = option;
                        break;
                case Opt_nobh:
                        set_opt(sbi->s_mount_opt, NOBH);
                        break;
                case Opt_bh:
                        clear_opt(sbi->s_mount_opt, NOBH);
                        break;
                case Opt_i_version:
                        set_opt(sbi->s_mount_opt, I_VERSION);
                        sb->s_flags |= MS_I_VERSION;
                        break;
                case Opt_nodelalloc:
                        clear_opt(sbi->s_mount_opt, DELALLOC);
                        break;
                case Opt_stripe:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0)
                                return 0;
                        sbi->s_stripe = option;
                        break;
                case Opt_delalloc:
                        set_opt(sbi->s_mount_opt, DELALLOC);
                        break;
                case Opt_block_validity:
                        set_opt(sbi->s_mount_opt, BLOCK_VALIDITY);
                        break;
                case Opt_noblock_validity:
                        clear_opt(sbi->s_mount_opt, BLOCK_VALIDITY);
                        break;
                case Opt_inode_readahead_blks:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0 || option > (1 << 30))
                                return 0;
                        if (!is_power_of_2(option)) {
                                ext4_msg(sb, KERN_ERR,
                                         "EXT4-fs: inode_readahead_blks"
                                         " must be a power of 2");
                                return 0;
                        }
                        sbi->s_inode_readahead_blks = option;
                        break;
                case Opt_journal_ioprio:
                        if (match_int(&args[0], &option))
                                return 0;
                        if (option < 0 || option > 7)
                                break;
                        *journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE,
                                                            option);
                        break;
                case Opt_noauto_da_alloc:
                        set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);
                        break;
                case Opt_auto_da_alloc:
                        if (match_int(&args[0], &option)) {
                                clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
                                break;
                        }
                        if (option)
                                clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);
                        else
                                set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);
                        break;
                default:
                        ext4_msg(sb, KERN_ERR,
                               "Unrecognized mount option \"%s\" "
                               "or missing value", p);
                        return 0;
                }
        }
#ifdef CONFIG_QUOTA
        if (sbi->s_qf_names[USRQUOTA] || sbi->s_qf_names[GRPQUOTA]) {
                if ((sbi->s_mount_opt & EXT4_MOUNT_USRQUOTA) &&
                     sbi->s_qf_names[USRQUOTA])
                        clear_opt(sbi->s_mount_opt, USRQUOTA);

                if ((sbi->s_mount_opt & EXT4_MOUNT_GRPQUOTA) &&
                     sbi->s_qf_names[GRPQUOTA])
                        clear_opt(sbi->s_mount_opt, GRPQUOTA);

                if ((sbi->s_qf_names[USRQUOTA] &&
                                (sbi->s_mount_opt & EXT4_MOUNT_GRPQUOTA)) ||
                    (sbi->s_qf_names[GRPQUOTA] &&
                                (sbi->s_mount_opt & EXT4_MOUNT_USRQUOTA))) {
                        ext4_msg(sb, KERN_ERR, "old and new quota "
                                        "format mixing");
                        return 0;
                }

                if (!sbi->s_jquota_fmt) {
                        ext4_msg(sb, KERN_ERR, "journaled quota format "
                                        "not specified");
                        return 0;
                }
        } else {
                if (sbi->s_jquota_fmt) {
                        ext4_msg(sb, KERN_ERR, "journaled quota format "
                                        "specified with no journaling "
                                        "enabled");
                        return 0;
                }
        }
#endif
        return 1;
}

static int ext4_setup_super(struct super_block *sb, struct ext4_super_block *es,
                            int read_only)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        int res = 0;

        if (le32_to_cpu(es->s_rev_level) > EXT4_MAX_SUPP_REV) {
                ext4_msg(sb, KERN_ERR, "revision level too high, "
                         "forcing read-only mode");
                res = MS_RDONLY;
        }
        if (read_only)
                return res;
        if (!(sbi->s_mount_state & EXT4_VALID_FS))
                ext4_msg(sb, KERN_WARNING, "warning: mounting unchecked fs, "
                         "running e2fsck is recommended");
        else if ((sbi->s_mount_state & EXT4_ERROR_FS))
                ext4_msg(sb, KERN_WARNING,
                         "warning: mounting fs with errors, "
                         "running e2fsck is recommended");
        else if ((__s16) le16_to_cpu(es->s_max_mnt_count) >= 0 &&
                 le16_to_cpu(es->s_mnt_count) >=
                 (unsigned short) (__s16) le16_to_cpu(es->s_max_mnt_count))
                ext4_msg(sb, KERN_WARNING,
                         "warning: maximal mount count reached, "
                         "running e2fsck is recommended");
        else if (le32_to_cpu(es->s_checkinterval) &&
                (le32_to_cpu(es->s_lastcheck) +
                        le32_to_cpu(es->s_checkinterval) <= get_seconds()))
                ext4_msg(sb, KERN_WARNING,
                         "warning: checktime reached, "
                         "running e2fsck is recommended");
        if (!sbi->s_journal)
                es->s_state &= cpu_to_le16(~EXT4_VALID_FS);
        if (!(__s16) le16_to_cpu(es->s_max_mnt_count))
                es->s_max_mnt_count = cpu_to_le16(EXT4_DFL_MAX_MNT_COUNT);
        le16_add_cpu(&es->s_mnt_count, 1);
        es->s_mtime = cpu_to_le32(get_seconds());
        ext4_update_dynamic_rev(sb);
        if (sbi->s_journal)
                EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);

        ext4_commit_super(sb, 1);
        if (test_opt(sb, DEBUG))
                printk(KERN_INFO "[EXT4 FS bs=%lu, gc=%u, "
                                "bpg=%lu, ipg=%lu, mo=%04x]\n",
                        sb->s_blocksize,
                        sbi->s_groups_count,
                        EXT4_BLOCKS_PER_GROUP(sb),
                        EXT4_INODES_PER_GROUP(sb),
                        sbi->s_mount_opt);

        if (EXT4_SB(sb)->s_journal) {
                ext4_msg(sb, KERN_INFO, "%s journal on %s",
                       EXT4_SB(sb)->s_journal->j_inode ? "internal" :
                       "external", EXT4_SB(sb)->s_journal->j_devname);
        } else {
                ext4_msg(sb, KERN_INFO, "no journal");
        }
        return res;
}

static int ext4_fill_flex_info(struct super_block *sb)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct ext4_group_desc *gdp = NULL;
        ext4_group_t flex_group_count;
        ext4_group_t flex_group;
        int groups_per_flex = 0;
        size_t size;
        int i;

        if (!sbi->s_es->s_log_groups_per_flex) {
                sbi->s_log_groups_per_flex = 0;
                return 1;
        }

        sbi->s_log_groups_per_flex = sbi->s_es->s_log_groups_per_flex;
        groups_per_flex = 1 << sbi->s_log_groups_per_flex;

        /* We allocate both existing and potentially added groups */
        flex_group_count = ((sbi->s_groups_count + groups_per_flex - 1) +
                        ((le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks) + 1) <<
                              EXT4_DESC_PER_BLOCK_BITS(sb))) / groups_per_flex;
        size = flex_group_count * sizeof(struct flex_groups);
        sbi->s_flex_groups = kzalloc(size, GFP_KERNEL);
        if (sbi->s_flex_groups == NULL) {
                sbi->s_flex_groups = vmalloc(size);
                if (sbi->s_flex_groups)
                        memset(sbi->s_flex_groups, 0, size);
        }
        if (sbi->s_flex_groups == NULL) {
                ext4_msg(sb, KERN_ERR, "not enough memory for "
                                "%u flex groups", flex_group_count);
                goto failed;
        }

        for (i = 0; i < sbi->s_groups_count; i++) {
                gdp = ext4_get_group_desc(sb, i, NULL);

                flex_group = ext4_flex_group(sbi, i);
                atomic_set(&sbi->s_flex_groups[flex_group].free_inodes,
                           ext4_free_inodes_count(sb, gdp));
                atomic_set(&sbi->s_flex_groups[flex_group].free_blocks,
                           ext4_free_blks_count(sb, gdp));
                atomic_set(&sbi->s_flex_groups[flex_group].used_dirs,
                           ext4_used_dirs_count(sb, gdp));
        }

        return 1;
failed:
        return 0;
}

__le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 block_group,
                            struct ext4_group_desc *gdp)
{
        __u16 crc = 0;

        if (sbi->s_es->s_feature_ro_compat &
            cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
                int offset = offsetof(struct ext4_group_desc, bg_checksum);
                __le32 le_group = cpu_to_le32(block_group);

                crc = crc16(~0, sbi->s_es->s_uuid, sizeof(sbi->s_es->s_uuid));
                crc = crc16(crc, (__u8 *)&le_group, sizeof(le_group));
                crc = crc16(crc, (__u8 *)gdp, offset);
                offset += sizeof(gdp->bg_checksum); /* skip checksum */
                /* for checksum of struct ext4_group_desc do the rest...*/
                if ((sbi->s_es->s_feature_incompat &
                     cpu_to_le32(EXT4_FEATURE_INCOMPAT_64BIT)) &&
                    offset < le16_to_cpu(sbi->s_es->s_desc_size))
                        crc = crc16(crc, (__u8 *)gdp + offset,
                                    le16_to_cpu(sbi->s_es->s_desc_size) -
                                        offset);
        }

        return cpu_to_le16(crc);
}

int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 block_group,
                                struct ext4_group_desc *gdp)
{
        if ((sbi->s_es->s_feature_ro_compat &
             cpu_to_le32(EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) &&
            (gdp->bg_checksum != ext4_group_desc_csum(sbi, block_group, gdp)))
                return 0;

        return 1;
}

/* Called at mount-time, super-block is locked */
static int ext4_check_descriptors(struct super_block *sb)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        ext4_fsblk_t first_block = le32_to_cpu(sbi->s_es->s_first_data_block);
        ext4_fsblk_t last_block;
        ext4_fsblk_t block_bitmap;
        ext4_fsblk_t inode_bitmap;
        ext4_fsblk_t inode_table;
        int flexbg_flag = 0;
        ext4_group_t i;

        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
                flexbg_flag = 1;

        ext4_debug("Checking group descriptors");

        for (i = 0; i < sbi->s_groups_count; i++) {
                struct ext4_group_desc *gdp = ext4_get_group_desc(sb, i, NULL);

                if (i == sbi->s_groups_count - 1 || flexbg_flag)
                        last_block = ext4_blocks_count(sbi->s_es) - 1;
                else
                        last_block = first_block +
                                (EXT4_BLOCKS_PER_GROUP(sb) - 1);

                block_bitmap = ext4_block_bitmap(sb, gdp);
                if (block_bitmap < first_block || block_bitmap > last_block) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                               "Block bitmap for group %u not in group "
                               "(block %llu)!", i, block_bitmap);
                        return 0;
                }
                inode_bitmap = ext4_inode_bitmap(sb, gdp);
                if (inode_bitmap < first_block || inode_bitmap > last_block) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                               "Inode bitmap for group %u not in group "
                               "(block %llu)!", i, inode_bitmap);
                        return 0;
                }
                inode_table = ext4_inode_table(sb, gdp);
                if (inode_table < first_block ||
                    inode_table + sbi->s_itb_per_group - 1 > last_block) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                               "Inode table for group %u not in group "
                               "(block %llu)!", i, inode_table);
                        return 0;
                }
                ext4_lock_group(sb, i);
                if (!ext4_group_desc_csum_verify(sbi, i, gdp)) {
                        ext4_msg(sb, KERN_ERR, "ext4_check_descriptors: "
                                 "Checksum for group %u failed (%u!=%u)",
                                 i, le16_to_cpu(ext4_group_desc_csum(sbi, i,
                                     gdp)), le16_to_cpu(gdp->bg_checksum));
                        if (!(sb->s_flags & MS_RDONLY)) {
                                ext4_unlock_group(sb, i);
                                return 0;
                        }
                }
                ext4_unlock_group(sb, i);
                if (!flexbg_flag)
                        first_block += EXT4_BLOCKS_PER_GROUP(sb);
        }

        ext4_free_blocks_count_set(sbi->s_es, ext4_count_free_blocks(sb));
        sbi->s_es->s_free_inodes_count =cpu_to_le32(ext4_count_free_inodes(sb));
        return 1;
}

/* ext4_orphan_cleanup() walks a singly-linked list of inodes (starting at
 * the superblock) which were deleted from all directories, but held open by
 * a process at the time of a crash.  We walk the list and try to delete these
 * inodes at recovery time (only with a read-write filesystem).
 *
 * In order to keep the orphan inode chain consistent during traversal (in
 * case of crash during recovery), we link each inode into the superblock
 * orphan list_head and handle it the same way as an inode deletion during
 * normal operation (which journals the operations for us).
 *
 * We only do an iget() and an iput() on each inode, which is very safe if we
 * accidentally point at an in-use or already deleted inode.  The worst that
 * can happen in this case is that we get a "bit already cleared" message from
 * ext4_free_inode().  The only reason we would point at a wrong inode is if
 * e2fsck was run on this filesystem, and it must have already done the orphan
 * inode cleanup for us, so we can safely abort without any further action.
 */
static void ext4_orphan_cleanup(struct super_block *sb,
                                struct ext4_super_block *es)
{
        unsigned int s_flags = sb->s_flags;
        int nr_orphans = 0, nr_truncates = 0;
#ifdef CONFIG_QUOTA
        int i;
#endif
        if (!es->s_last_orphan) {
                jbd_debug(4, "no orphan inodes to clean up\n");
                return;
        }

        if (bdev_read_only(sb->s_bdev)) {
                ext4_msg(sb, KERN_ERR, "write access "
                        "unavailable, skipping orphan cleanup");
                return;
        }

        if (EXT4_SB(sb)->s_mount_state & EXT4_ERROR_FS) {
                if (es->s_last_orphan)
                        jbd_debug(1, "Errors on filesystem, "
                                  "clearing orphan list.\n");
                es->s_last_orphan = 0;
                jbd_debug(1, "Skipping orphan recovery on fs with errors.\n");
                return;
        }

        if (s_flags & MS_RDONLY) {
                ext4_msg(sb, KERN_INFO, "orphan cleanup on readonly fs");
                sb->s_flags &= ~MS_RDONLY;
        }
#ifdef CONFIG_QUOTA
        /* Needed for iput() to work correctly and not trash data */
        sb->s_flags |= MS_ACTIVE;
        /* Turn on quotas so that they are updated correctly */
        for (i = 0; i < MAXQUOTAS; i++) {
                if (EXT4_SB(sb)->s_qf_names[i]) {
                        int ret = ext4_quota_on_mount(sb, i);
                        if (ret < 0)
                                ext4_msg(sb, KERN_ERR,
                                        "Cannot turn on journaled "
                                        "quota: error %d", ret);
                }
        }
#endif

        while (es->s_last_orphan) {
                struct inode *inode;

                inode = ext4_orphan_get(sb, le32_to_cpu(es->s_last_orphan));
                if (IS_ERR(inode)) {
                        es->s_last_orphan = 0;
                        break;
                }

                list_add(&EXT4_I(inode)->i_orphan, &EXT4_SB(sb)->s_orphan);
                vfs_dq_init(inode);
                if (inode->i_nlink) {
                        ext4_msg(sb, KERN_DEBUG,
                                "%s: truncating inode %lu to %lld bytes",
                                __func__, inode->i_ino, inode->i_size);
                        jbd_debug(2, "truncating inode %lu to %lld bytes\n",
                                  inode->i_ino, inode->i_size);
                        ext4_truncate(inode);
                        nr_truncates++;
                } else {
                        ext4_msg(sb, KERN_DEBUG,
                                "%s: deleting unreferenced inode %lu",
                                __func__, inode->i_ino);
                        jbd_debug(2, "deleting unreferenced inode %lu\n",
                                  inode->i_ino);
                        nr_orphans++;
                }
                iput(inode);  /* The delete magic happens here! */
        }

#define PLURAL(x) (x), ((x) == 1) ? "" : "s"

        if (nr_orphans)
                ext4_msg(sb, KERN_INFO, "%d orphan inode%s deleted",
                       PLURAL(nr_orphans));
        if (nr_truncates)
                ext4_msg(sb, KERN_INFO, "%d truncate%s cleaned up",
                       PLURAL(nr_truncates));
#ifdef CONFIG_QUOTA
        /* Turn quotas off */
        for (i = 0; i < MAXQUOTAS; i++) {
                if (sb_dqopt(sb)->files[i])
                        vfs_quota_off(sb, i, 0);
        }
#endif
        sb->s_flags = s_flags; /* Restore MS_RDONLY status */
}

/*
 * Maximal extent format file size.
 * Resulting logical blkno at s_maxbytes must fit in our on-disk
 * extent format containers, within a sector_t, and within i_blocks
 * in the vfs.  ext4 inode has 48 bits of i_block in fsblock units,
 * so that won't be a limiting factor.
 *
 * Note, this does *not* consider any metadata overhead for vfs i_blocks.
 */
static loff_t ext4_max_size(int blkbits, int has_huge_files)
{
        loff_t res;
        loff_t upper_limit = MAX_LFS_FILESIZE;

        /* small i_blocks in vfs inode? */
        if (!has_huge_files || sizeof(blkcnt_t) < sizeof(u64)) {
                /*
                 * CONFIG_LBDAF is not enabled implies the inode
                 * i_block represent total blocks in 512 bytes
                 * 32 == size of vfs inode i_blocks * 8
                 */
                upper_limit = (1LL << 32) - 1;

                /* total blocks in file system block size */
                upper_limit >>= (blkbits - 9);
                upper_limit <<= blkbits;
        }

        /* 32-bit extent-start container, ee_block */
        res = 1LL << 32;
        res <<= blkbits;
        res -= 1;

        /* Sanity check against vm- & vfs- imposed limits */
        if (res > upper_limit)
                res = upper_limit;

        return res;
}

/*
 * Maximal bitmap file size.  There is a direct, and {,double-,triple-}indirect
 * block limit, and also a limit of (2^48 - 1) 512-byte sectors in i_blocks.
 * We need to be 1 filesystem block less than the 2^48 sector limit.
 */
static loff_t ext4_max_bitmap_size(int bits, int has_huge_files)
{
        loff_t res = EXT4_NDIR_BLOCKS;
        int meta_blocks;
        loff_t upper_limit;
        /* This is calculated to be the largest file size for a dense, block
         * mapped file such that the file's total number of 512-byte sectors,
         * including data and all indirect blocks, does not exceed (2^48 - 1).
         *
         * __u32 i_blocks_lo and _u16 i_blocks_high represent the total
         * number of 512-byte sectors of the file.
         */

        if (!has_huge_files || sizeof(blkcnt_t) < sizeof(u64)) {
                /*
                 * !has_huge_files or CONFIG_LBDAF not enabled implies that
                 * the inode i_block field represents total file blocks in
                 * 2^32 512-byte sectors == size of vfs inode i_blocks * 8
                 */
                upper_limit = (1LL << 32) - 1;

                /* total blocks in file system block size */
                upper_limit >>= (bits - 9);

        } else {
                /*
                 * We use 48 bit ext4_inode i_blocks
                 * With EXT4_HUGE_FILE_FL set the i_blocks
                 * represent total number of blocks in
                 * file system block size
                 */
                upper_limit = (1LL << 48) - 1;

        }

        /* indirect blocks */
        meta_blocks = 1;
        /* double indirect blocks */
        meta_blocks += 1 + (1LL << (bits-2));
        /* tripple indirect blocks */
        meta_blocks += 1 + (1LL << (bits-2)) + (1LL << (2*(bits-2)));

        upper_limit -= meta_blocks;
        upper_limit <<= bits;

        res += 1LL << (bits-2);
        res += 1LL << (2*(bits-2));
        res += 1LL << (3*(bits-2));
        res <<= bits;
        if (res > upper_limit)
                res = upper_limit;

        if (res > MAX_LFS_FILESIZE)
                res = MAX_LFS_FILESIZE;

        return res;
}

static ext4_fsblk_t descriptor_loc(struct super_block *sb,
                                   ext4_fsblk_t logical_sb_block, int nr)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        ext4_group_t bg, first_meta_bg;
        int has_super = 0;

        first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);

        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_META_BG) ||
            nr < first_meta_bg)
                return logical_sb_block + nr + 1;
        bg = sbi->s_desc_per_block * nr;
        if (ext4_bg_has_super(sb, bg))
                has_super = 1;

        return (has_super + ext4_group_first_block_no(sb, bg));
}

/**
 * ext4_get_stripe_size: Get the stripe size.
 * @sbi: In memory super block info
 *
 * If we have specified it via mount option, then
 * use the mount option value. If the value specified at mount time is
 * greater than the blocks per group use the super block value.
 * If the super block value is greater than blocks per group return 0.
 * Allocator needs it be less than blocks per group.
 *
 */
static unsigned long ext4_get_stripe_size(struct ext4_sb_info *sbi)
{
        unsigned long stride = le16_to_cpu(sbi->s_es->s_raid_stride);
        unsigned long stripe_width =
                        le32_to_cpu(sbi->s_es->s_raid_stripe_width);

        if (sbi->s_stripe && sbi->s_stripe <= sbi->s_blocks_per_group)
                return sbi->s_stripe;

        if (stripe_width <= sbi->s_blocks_per_group)
                return stripe_width;

        if (stride <= sbi->s_blocks_per_group)
                return stride;

        return 0;
}

/* sysfs supprt */

struct ext4_attr {
        struct attribute attr;
        ssize_t (*show)(struct ext4_attr *, struct ext4_sb_info *, char *);
        ssize_t (*store)(struct ext4_attr *, struct ext4_sb_info *, 
                         const char *, size_t);
        int offset;
};

static int parse_strtoul(const char *buf,
                unsigned long max, unsigned long *value)
{
        char *endp;

        while (*buf && isspace(*buf))
                buf++;
        *value = simple_strtoul(buf, &endp, 0);
        while (*endp && isspace(*endp))
                endp++;
        if (*endp || *value > max)
                return -EINVAL;

        return 0;
}

static ssize_t delayed_allocation_blocks_show(struct ext4_attr *a,
                                              struct ext4_sb_info *sbi,
                                              char *buf)
{
        return snprintf(buf, PAGE_SIZE, "%llu\n",
                        (s64) percpu_counter_sum(&sbi->s_dirtyblocks_counter));
}

static ssize_t session_write_kbytes_show(struct ext4_attr *a,
                                         struct ext4_sb_info *sbi, char *buf)
{
        struct super_block *sb = sbi->s_buddy_cache->i_sb;

        return snprintf(buf, PAGE_SIZE, "%lu\n",
                        (part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                         sbi->s_sectors_written_start) >> 1);
}

static ssize_t lifetime_write_kbytes_show(struct ext4_attr *a,
                                          struct ext4_sb_info *sbi, char *buf)
{
        struct super_block *sb = sbi->s_buddy_cache->i_sb;

        return snprintf(buf, PAGE_SIZE, "%llu\n",
                        sbi->s_kbytes_written + 
                        ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                          EXT4_SB(sb)->s_sectors_written_start) >> 1));
}

static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
                                          struct ext4_sb_info *sbi,
                                          const char *buf, size_t count)
{
        unsigned long t;

        if (parse_strtoul(buf, 0x40000000, &t))
                return -EINVAL;

        if (!is_power_of_2(t))
                return -EINVAL;

        sbi->s_inode_readahead_blks = t;
        return count;
}

static ssize_t sbi_ui_show(struct ext4_attr *a,
                           struct ext4_sb_info *sbi, char *buf)
{
        unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);

        return snprintf(buf, PAGE_SIZE, "%u\n", *ui);
}

static ssize_t sbi_ui_store(struct ext4_attr *a,
                            struct ext4_sb_info *sbi,
                            const char *buf, size_t count)
{
        unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
        unsigned long t;

        if (parse_strtoul(buf, 0xffffffff, &t))
                return -EINVAL;
        *ui = t;
        return count;
}

#define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname) \
static struct ext4_attr ext4_attr_##_name = {                   \
        .attr = {.name = __stringify(_name), .mode = _mode },   \
        .show   = _show,                                        \
        .store  = _store,                                       \
        .offset = offsetof(struct ext4_sb_info, _elname),       \
}
#define EXT4_ATTR(name, mode, show, store) \
static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)

#define EXT4_RO_ATTR(name) EXT4_ATTR(name, 0444, name##_show, NULL)
#define EXT4_RW_ATTR(name) EXT4_ATTR(name, 0644, name##_show, name##_store)
#define EXT4_RW_ATTR_SBI_UI(name, elname)       \
        EXT4_ATTR_OFFSET(name, 0644, sbi_ui_show, sbi_ui_store, elname)
#define ATTR_LIST(name) &ext4_attr_##name.attr

EXT4_RO_ATTR(delayed_allocation_blocks);
EXT4_RO_ATTR(session_write_kbytes);
EXT4_RO_ATTR(lifetime_write_kbytes);
EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
                 inode_readahead_blks_store, s_inode_readahead_blks);
EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
EXT4_RW_ATTR_SBI_UI(mb_min_to_scan, s_mb_min_to_scan);
EXT4_RW_ATTR_SBI_UI(mb_order2_req, s_mb_order2_reqs);
EXT4_RW_ATTR_SBI_UI(mb_stream_req, s_mb_stream_request);
EXT4_RW_ATTR_SBI_UI(mb_group_prealloc, s_mb_group_prealloc);

static struct attribute *ext4_attrs[] = {
        ATTR_LIST(delayed_allocation_blocks),
        ATTR_LIST(session_write_kbytes),
        ATTR_LIST(lifetime_write_kbytes),
        ATTR_LIST(inode_readahead_blks),
        ATTR_LIST(inode_goal),
        ATTR_LIST(mb_stats),
        ATTR_LIST(mb_max_to_scan),
        ATTR_LIST(mb_min_to_scan),
        ATTR_LIST(mb_order2_req),
        ATTR_LIST(mb_stream_req),
        ATTR_LIST(mb_group_prealloc),
        NULL,
};

static ssize_t ext4_attr_show(struct kobject *kobj,
                              struct attribute *attr, char *buf)
{
        struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                                                s_kobj);
        struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);

        return a->show ? a->show(a, sbi, buf) : 0;
}

static ssize_t ext4_attr_store(struct kobject *kobj,
                               struct attribute *attr,
                               const char *buf, size_t len)
{
        struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                                                s_kobj);
        struct ext4_attr *a = container_of(attr, struct ext4_attr, attr);

        return a->store ? a->store(a, sbi, buf, len) : 0;
}

static void ext4_sb_release(struct kobject *kobj)
{
        struct ext4_sb_info *sbi = container_of(kobj, struct ext4_sb_info,
                                                s_kobj);
        complete(&sbi->s_kobj_unregister);
}


static struct sysfs_ops ext4_attr_ops = {
        .show   = ext4_attr_show,
        .store  = ext4_attr_store,
};

static struct kobj_type ext4_ktype = {
        .default_attrs  = ext4_attrs,
        .sysfs_ops      = &ext4_attr_ops,
        .release        = ext4_sb_release,
};

/*
 * Check whether this filesystem can be mounted based on
 * the features present and the RDONLY/RDWR mount requested.
 * Returns 1 if this filesystem can be mounted as requested,
 * 0 if it cannot be.
 */
static int ext4_feature_set_ok(struct super_block *sb, int readonly)
{
        if (EXT4_HAS_INCOMPAT_FEATURE(sb, ~EXT4_FEATURE_INCOMPAT_SUPP)) {
                ext4_msg(sb, KERN_ERR,
                        "Couldn't mount because of "
                        "unsupported optional features (%x)",
                        (le32_to_cpu(EXT4_SB(sb)->s_es->s_feature_incompat) &
                        ~EXT4_FEATURE_INCOMPAT_SUPP));
                return 0;
        }

        if (readonly)
                return 1;

        /* Check that feature set is OK for a read-write mount */
        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, ~EXT4_FEATURE_RO_COMPAT_SUPP)) {
                ext4_msg(sb, KERN_ERR, "couldn't mount RDWR because of "
                         "unsupported optional features (%x)",
                         (le32_to_cpu(EXT4_SB(sb)->s_es->s_feature_ro_compat) &
                                ~EXT4_FEATURE_RO_COMPAT_SUPP));
                return 0;
        }
        /*
         * Large file size enabled file system can only be mounted
         * read-write on 32-bit systems if kernel is built with CONFIG_LBDAF
         */
        if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_HUGE_FILE)) {
                if (sizeof(blkcnt_t) < sizeof(u64)) {
                        ext4_msg(sb, KERN_ERR, "Filesystem with huge files "
                                 "cannot be mounted RDWR without "
                                 "CONFIG_LBDAF");
                        return 0;
                }
        }
        return 1;
}

static int ext4_fill_super(struct super_block *sb, void *data, int silent)
                                __releases(kernel_lock)
                                __acquires(kernel_lock)
{
        struct buffer_head *bh;
        struct ext4_super_block *es = NULL;
        struct ext4_sb_info *sbi;
        ext4_fsblk_t block;
        ext4_fsblk_t sb_block = get_sb_block(&data);
        ext4_fsblk_t logical_sb_block;
        unsigned long offset = 0;
        unsigned long journal_devnum = 0;
        unsigned long def_mount_opts;
        struct inode *root;
        char *cp;
        const char *descr;
        int ret = -EINVAL;
        int blocksize;
        unsigned int db_count;
        unsigned int i;
        int needs_recovery, has_huge_files;
        __u64 blocks_count;
        int err;
        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;

        sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
        if (!sbi)
                return -ENOMEM;

        sbi->s_blockgroup_lock =
                kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
        if (!sbi->s_blockgroup_lock) {
                kfree(sbi);
                return -ENOMEM;
        }
        sb->s_fs_info = sbi;
        sbi->s_mount_opt = 0;
        sbi->s_resuid = EXT4_DEF_RESUID;
        sbi->s_resgid = EXT4_DEF_RESGID;
        sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
        sbi->s_sb_block = sb_block;
        sbi->s_sectors_written_start = part_stat_read(sb->s_bdev->bd_part,
                                                      sectors[1]);

        unlock_kernel();

        /* Cleanup superblock name */
        for (cp = sb->s_id; (cp = strchr(cp, '/'));)
                *cp = '!';

        blocksize = sb_min_blocksize(sb, EXT4_MIN_BLOCK_SIZE);
        if (!blocksize) {
                ext4_msg(sb, KERN_ERR, "unable to set blocksize");
                goto out_fail;
        }

        /*
         * The ext4 superblock will not be buffer aligned for other than 1kB
         * block sizes.  We need to calculate the offset from buffer start.
         */
        if (blocksize != EXT4_MIN_BLOCK_SIZE) {
                logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
                offset = do_div(logical_sb_block, blocksize);
        } else {
                logical_sb_block = sb_block;
        }

        if (!(bh = sb_bread(sb, logical_sb_block))) {
                ext4_msg(sb, KERN_ERR, "unable to read superblock");
                goto out_fail;
        }
        /*
         * Note: s_es must be initialized as soon as possible because
         *       some ext4 macro-instructions depend on its value
         */
        es = (struct ext4_super_block *) (((char *)bh->b_data) + offset);
        sbi->s_es = es;
        sb->s_magic = le16_to_cpu(es->s_magic);
        if (sb->s_magic != EXT4_SUPER_MAGIC)
                goto cantfind_ext4;
        sbi->s_kbytes_written = le64_to_cpu(es->s_kbytes_written);

        /* Set defaults before we parse the mount options */
        def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
        if (def_mount_opts & EXT4_DEFM_DEBUG)
                set_opt(sbi->s_mount_opt, DEBUG);
        if (def_mount_opts & EXT4_DEFM_BSDGROUPS)
                set_opt(sbi->s_mount_opt, GRPID);
        if (def_mount_opts & EXT4_DEFM_UID16)
                set_opt(sbi->s_mount_opt, NO_UID32);
#ifdef CONFIG_EXT4_FS_XATTR
        if (def_mount_opts & EXT4_DEFM_XATTR_USER)
                set_opt(sbi->s_mount_opt, XATTR_USER);
#endif
#ifdef CONFIG_EXT4_FS_POSIX_ACL
        if (def_mount_opts & EXT4_DEFM_ACL)
                set_opt(sbi->s_mount_opt, POSIX_ACL);
#endif
        if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_DATA)
                sbi->s_mount_opt |= EXT4_MOUNT_JOURNAL_DATA;
        else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_ORDERED)
                sbi->s_mount_opt |= EXT4_MOUNT_ORDERED_DATA;
        else if ((def_mount_opts & EXT4_DEFM_JMODE) == EXT4_DEFM_JMODE_WBACK)
                sbi->s_mount_opt |= EXT4_MOUNT_WRITEBACK_DATA;

        if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_PANIC)
                set_opt(sbi->s_mount_opt, ERRORS_PANIC);
        else if (le16_to_cpu(sbi->s_es->s_errors) == EXT4_ERRORS_CONTINUE)
                set_opt(sbi->s_mount_opt, ERRORS_CONT);
        else
                set_opt(sbi->s_mount_opt, ERRORS_RO);

        sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
        sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
        sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
        sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
        sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
        sbi->s_mb_history_max = default_mb_history_length;

        set_opt(sbi->s_mount_opt, BARRIER);

        /*
         * enable delayed allocation by default
         * Use -o nodelalloc to turn it off
         */
        set_opt(sbi->s_mount_opt, DELALLOC);

        if (!parse_options((char *) data, sb, &journal_devnum,
                           &journal_ioprio, NULL, 0))
                goto failed_mount;

        sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                ((sbi->s_mount_opt & EXT4_MOUNT_POSIX_ACL) ? MS_POSIXACL : 0);

        if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV &&
            (EXT4_HAS_COMPAT_FEATURE(sb, ~0U) ||
             EXT4_HAS_RO_COMPAT_FEATURE(sb, ~0U) ||
             EXT4_HAS_INCOMPAT_FEATURE(sb, ~0U)))
                ext4_msg(sb, KERN_WARNING,
                       "feature flags set on rev 0 fs, "
                       "running e2fsck is recommended");

        /*
         * Check feature flags regardless of the revision level, since we
         * previously didn't change the revision level when setting the flags,
         * so there is a chance incompat flags are set on a rev 0 filesystem.
         */
        if (!ext4_feature_set_ok(sb, (sb->s_flags & MS_RDONLY)))
                goto failed_mount;

        blocksize = BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);

        if (blocksize < EXT4_MIN_BLOCK_SIZE ||
            blocksize > EXT4_MAX_BLOCK_SIZE) {
                ext4_msg(sb, KERN_ERR,
                       "Unsupported filesystem blocksize %d", blocksize);
                goto failed_mount;
        }

        if (sb->s_blocksize != blocksize) {
                /* Validate the filesystem blocksize */
                if (!sb_set_blocksize(sb, blocksize)) {
                        ext4_msg(sb, KERN_ERR, "bad block size %d",
                                        blocksize);
                        goto failed_mount;
                }

                brelse(bh);
                logical_sb_block = sb_block * EXT4_MIN_BLOCK_SIZE;
                offset = do_div(logical_sb_block, blocksize);
                bh = sb_bread(sb, logical_sb_block);
                if (!bh) {
                        ext4_msg(sb, KERN_ERR,
                               "Can't read superblock on 2nd try");
                        goto failed_mount;
                }
                es = (struct ext4_super_block *)(((char *)bh->b_data) + offset);
                sbi->s_es = es;
                if (es->s_magic != cpu_to_le16(EXT4_SUPER_MAGIC)) {
                        ext4_msg(sb, KERN_ERR,
                               "Magic mismatch, very weird!");
                        goto failed_mount;
                }
        }

        has_huge_files = EXT4_HAS_RO_COMPAT_FEATURE(sb,
                                EXT4_FEATURE_RO_COMPAT_HUGE_FILE);
        sbi->s_bitmap_maxbytes = ext4_max_bitmap_size(sb->s_blocksize_bits,
                                                      has_huge_files);
        sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);

        if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
                sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
                sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
        } else {
                sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
                sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
                if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
                    (!is_power_of_2(sbi->s_inode_size)) ||
                    (sbi->s_inode_size > blocksize)) {
                        ext4_msg(sb, KERN_ERR,
                               "unsupported inode size: %d",
                               sbi->s_inode_size);
                        goto failed_mount;
                }
                if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE)
                        sb->s_time_gran = 1 << (EXT4_EPOCH_BITS - 2);
        }

        sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_64BIT)) {
                if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
                    sbi->s_desc_size > EXT4_MAX_DESC_SIZE ||
                    !is_power_of_2(sbi->s_desc_size)) {
                        ext4_msg(sb, KERN_ERR,
                               "unsupported descriptor size %lu",
                               sbi->s_desc_size);
                        goto failed_mount;
                }
        } else
                sbi->s_desc_size = EXT4_MIN_DESC_SIZE;

        sbi->s_blocks_per_group = le32_to_cpu(es->s_blocks_per_group);
        sbi->s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
        if (EXT4_INODE_SIZE(sb) == 0 || EXT4_INODES_PER_GROUP(sb) == 0)
                goto cantfind_ext4;

        sbi->s_inodes_per_block = blocksize / EXT4_INODE_SIZE(sb);
        if (sbi->s_inodes_per_block == 0)
                goto cantfind_ext4;
        sbi->s_itb_per_group = sbi->s_inodes_per_group /
                                        sbi->s_inodes_per_block;
        sbi->s_desc_per_block = blocksize / EXT4_DESC_SIZE(sb);
        sbi->s_sbh = bh;
        sbi->s_mount_state = le16_to_cpu(es->s_state);
        sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb));
        sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb));

        for (i = 0; i < 4; i++)
                sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
        sbi->s_def_hash_version = es->s_def_hash_version;
        i = le32_to_cpu(es->s_flags);
        if (i & EXT2_FLAGS_UNSIGNED_HASH)
                sbi->s_hash_unsigned = 3;
        else if ((i & EXT2_FLAGS_SIGNED_HASH) == 0) {
#ifdef __CHAR_UNSIGNED__
                es->s_flags |= cpu_to_le32(EXT2_FLAGS_UNSIGNED_HASH);
                sbi->s_hash_unsigned = 3;
#else
                es->s_flags |= cpu_to_le32(EXT2_FLAGS_SIGNED_HASH);
#endif
                sb->s_dirt = 1;
        }

        if (sbi->s_blocks_per_group > blocksize * 8) {
                ext4_msg(sb, KERN_ERR,
                       "#blocks per group too big: %lu",
                       sbi->s_blocks_per_group);
                goto failed_mount;
        }
        if (sbi->s_inodes_per_group > blocksize * 8) {
                ext4_msg(sb, KERN_ERR,
                       "#inodes per group too big: %lu",
                       sbi->s_inodes_per_group);
                goto failed_mount;
        }

        /*
         * Test whether we have more sectors than will fit in sector_t,
         * and whether the max offset is addressable by the page cache.
         */
        if ((ext4_blocks_count(es) >
             (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) ||
            (ext4_blocks_count(es) >
             (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - sb->s_blocksize_bits))) {
                ext4_msg(sb, KERN_ERR, "filesystem"
                         " too large to mount safely on this system");
                if (sizeof(sector_t) < 8)
                        ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
                ret = -EFBIG;
                goto failed_mount;
        }

        if (EXT4_BLOCKS_PER_GROUP(sb) == 0)
                goto cantfind_ext4;

        /* check blocks count against device size */
        blocks_count = sb->s_bdev->bd_inode->i_size >> sb->s_blocksize_bits;
        if (blocks_count && ext4_blocks_count(es) > blocks_count) {
                ext4_msg(sb, KERN_WARNING, "bad geometry: block count %llu "
                       "exceeds size of device (%llu blocks)",
                       ext4_blocks_count(es), blocks_count);
                goto failed_mount;
        }

        /*
         * It makes no sense for the first data block to be beyond the end
         * of the filesystem.
         */
        if (le32_to_cpu(es->s_first_data_block) >= ext4_blocks_count(es)) {
                ext4_msg(sb, KERN_WARNING, "bad geometry: first data"
                         "block %u is beyond end of filesystem (%llu)",
                         le32_to_cpu(es->s_first_data_block),
                         ext4_blocks_count(es));
                goto failed_mount;
        }
        blocks_count = (ext4_blocks_count(es) -
                        le32_to_cpu(es->s_first_data_block) +
                        EXT4_BLOCKS_PER_GROUP(sb) - 1);
        do_div(blocks_count, EXT4_BLOCKS_PER_GROUP(sb));
        if (blocks_count > ((uint64_t)1<<32) - EXT4_DESC_PER_BLOCK(sb)) {
                ext4_msg(sb, KERN_WARNING, "groups count too large: %u "
                       "(block count %llu, first data block %u, "
                       "blocks per group %lu)", sbi->s_groups_count,
                       ext4_blocks_count(es),
                       le32_to_cpu(es->s_first_data_block),
                       EXT4_BLOCKS_PER_GROUP(sb));
                goto failed_mount;
        }
        sbi->s_groups_count = blocks_count;
        db_count = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) - 1) /
                   EXT4_DESC_PER_BLOCK(sb);
        sbi->s_group_desc = kmalloc(db_count * sizeof(struct buffer_head *),
                                    GFP_KERNEL);
        if (sbi->s_group_desc == NULL) {
                ext4_msg(sb, KERN_ERR, "not enough memory");
                goto failed_mount;
        }

#ifdef CONFIG_PROC_FS
        if (ext4_proc_root)
                sbi->s_proc = proc_mkdir(sb->s_id, ext4_proc_root);
#endif

        bgl_lock_init(sbi->s_blockgroup_lock);

        for (i = 0; i < db_count; i++) {
                block = descriptor_loc(sb, logical_sb_block, i);
                sbi->s_group_desc[i] = sb_bread(sb, block);
                if (!sbi->s_group_desc[i]) {
                        ext4_msg(sb, KERN_ERR,
                               "can't read group descriptor %d", i);
                        db_count = i;
                        goto failed_mount2;
                }
        }
        if (!ext4_check_descriptors(sb)) {
                ext4_msg(sb, KERN_ERR, "group descriptors corrupted!");
                goto failed_mount2;
        }
        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
                if (!ext4_fill_flex_info(sb)) {
                        ext4_msg(sb, KERN_ERR,
                               "unable to initialize "
                               "flex_bg meta info!");
                        goto failed_mount2;
                }

        sbi->s_gdb_count = db_count;
        get_random_bytes(&sbi->s_next_generation, sizeof(u32));
        spin_lock_init(&sbi->s_next_gen_lock);

        err = percpu_counter_init(&sbi->s_freeblocks_counter,
                        ext4_count_free_blocks(sb));
        if (!err) {
                err = percpu_counter_init(&sbi->s_freeinodes_counter,
                                ext4_count_free_inodes(sb));
        }
        if (!err) {
                err = percpu_counter_init(&sbi->s_dirs_counter,
                                ext4_count_dirs(sb));
        }
        if (!err) {
                err = percpu_counter_init(&sbi->s_dirtyblocks_counter, 0);
        }
        if (err) {
                ext4_msg(sb, KERN_ERR, "insufficient memory");
                goto failed_mount3;
        }

        sbi->s_stripe = ext4_get_stripe_size(sbi);

        /*
         * set up enough so that it can read an inode
         */
        if (!test_opt(sb, NOLOAD) &&
            EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
                sb->s_op = &ext4_sops;
        else
                sb->s_op = &ext4_nojournal_sops;
        sb->s_export_op = &ext4_export_ops;
        sb->s_xattr = ext4_xattr_handlers;
#ifdef CONFIG_QUOTA
        sb->s_qcop = &ext4_qctl_operations;
        sb->dq_op = &ext4_quota_operations;
#endif
        INIT_LIST_HEAD(&sbi->s_orphan); /* unlinked but open files */
        mutex_init(&sbi->s_orphan_lock);
        mutex_init(&sbi->s_resize_lock);

        sb->s_root = NULL;

        needs_recovery = (es->s_last_orphan != 0 ||
                          EXT4_HAS_INCOMPAT_FEATURE(sb,
                                    EXT4_FEATURE_INCOMPAT_RECOVER));

        /*
         * The first inode we look at is the journal inode.  Don't try
         * root first: it may be modified in the journal!
         */
        if (!test_opt(sb, NOLOAD) &&
            EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
                if (ext4_load_journal(sb, es, journal_devnum))
                        goto failed_mount3;
                if (!(sb->s_flags & MS_RDONLY) &&
                    EXT4_SB(sb)->s_journal->j_failed_commit) {
                        ext4_msg(sb, KERN_CRIT, "error: "
                               "ext4_fill_super: Journal transaction "
                               "%u is corrupt",
                               EXT4_SB(sb)->s_journal->j_failed_commit);
                        if (test_opt(sb, ERRORS_RO)) {
                                ext4_msg(sb, KERN_CRIT,
                                       "Mounting filesystem read-only");
                                sb->s_flags |= MS_RDONLY;
                                EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
                                es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
                        }
                        if (test_opt(sb, ERRORS_PANIC)) {
                                EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
                                es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
                                ext4_commit_super(sb, 1);
                                goto failed_mount4;
                        }
                }
        } else if (test_opt(sb, NOLOAD) && !(sb->s_flags & MS_RDONLY) &&
              EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER)) {
                ext4_msg(sb, KERN_ERR, "required journal recovery "
                       "suppressed and not mounted read-only");
                goto failed_mount4;
        } else {
                clear_opt(sbi->s_mount_opt, DATA_FLAGS);
                set_opt(sbi->s_mount_opt, WRITEBACK_DATA);
                sbi->s_journal = NULL;
                needs_recovery = 0;
                goto no_journal;
        }

        if (ext4_blocks_count(es) > 0xffffffffULL &&
            !jbd2_journal_set_features(EXT4_SB(sb)->s_journal, 0, 0,
                                       JBD2_FEATURE_INCOMPAT_64BIT)) {
                ext4_msg(sb, KERN_ERR, "Failed to set 64-bit journal feature");
                goto failed_mount4;
        }

        if (test_opt(sb, JOURNAL_ASYNC_COMMIT)) {
                jbd2_journal_set_features(sbi->s_journal,
                                JBD2_FEATURE_COMPAT_CHECKSUM, 0,
                                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
        } else if (test_opt(sb, JOURNAL_CHECKSUM)) {
                jbd2_journal_set_features(sbi->s_journal,
                                JBD2_FEATURE_COMPAT_CHECKSUM, 0, 0);
                jbd2_journal_clear_features(sbi->s_journal, 0, 0,
                                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
        } else {
                jbd2_journal_clear_features(sbi->s_journal,
                                JBD2_FEATURE_COMPAT_CHECKSUM, 0,
                                JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT);
        }

        /* We have now updated the journal if required, so we can
         * validate the data journaling mode. */
        switch (test_opt(sb, DATA_FLAGS)) {
        case 0:
                /* No mode set, assume a default based on the journal
                 * capabilities: ORDERED_DATA if the journal can
                 * cope, else JOURNAL_DATA
                 */
                if (jbd2_journal_check_available_features
                    (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE))
                        set_opt(sbi->s_mount_opt, ORDERED_DATA);
                else
                        set_opt(sbi->s_mount_opt, JOURNAL_DATA);
                break;

        case EXT4_MOUNT_ORDERED_DATA:
        case EXT4_MOUNT_WRITEBACK_DATA:
                if (!jbd2_journal_check_available_features
                    (sbi->s_journal, 0, 0, JBD2_FEATURE_INCOMPAT_REVOKE)) {
                        ext4_msg(sb, KERN_ERR, "Journal does not support "
                               "requested data journaling mode");
                        goto failed_mount4;
                }
        default:
                break;
        }
        set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);

no_journal:

        if (test_opt(sb, NOBH)) {
                if (!(test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_WRITEBACK_DATA)) {
                        ext4_msg(sb, KERN_WARNING, "Ignoring nobh option - "
                                "its supported only with writeback mode");
                        clear_opt(sbi->s_mount_opt, NOBH);
                }
        }
        /*
         * The jbd2_journal_load will have done any necessary log recovery,
         * so we can safely mount the rest of the filesystem now.
         */

        root = ext4_iget(sb, EXT4_ROOT_INO);
        if (IS_ERR(root)) {
                ext4_msg(sb, KERN_ERR, "get root inode failed");
                ret = PTR_ERR(root);
                goto failed_mount4;
        }
        if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
                iput(root);
                ext4_msg(sb, KERN_ERR, "corrupt root inode, run e2fsck");
                goto failed_mount4;
        }
        sb->s_root = d_alloc_root(root);
        if (!sb->s_root) {
                ext4_msg(sb, KERN_ERR, "get root dentry failed");
                iput(root);
                ret = -ENOMEM;
                goto failed_mount4;
        }

        ext4_setup_super(sb, es, sb->s_flags & MS_RDONLY);

        /* determine the minimum size of new large inodes, if present */
        if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
                sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
                                                     EXT4_GOOD_OLD_INODE_SIZE;
                if (EXT4_HAS_RO_COMPAT_FEATURE(sb,
                                       EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE)) {
                        if (sbi->s_want_extra_isize <
                            le16_to_cpu(es->s_want_extra_isize))
                                sbi->s_want_extra_isize =
                                        le16_to_cpu(es->s_want_extra_isize);
                        if (sbi->s_want_extra_isize <
                            le16_to_cpu(es->s_min_extra_isize))
                                sbi->s_want_extra_isize =
                                        le16_to_cpu(es->s_min_extra_isize);
                }
        }
        /* Check if enough inode space is available */
        if (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
                                                        sbi->s_inode_size) {
                sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
                                                       EXT4_GOOD_OLD_INODE_SIZE;
                ext4_msg(sb, KERN_INFO, "required extra inode space not"
                         "available");
        }

        if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
                ext4_msg(sb, KERN_WARNING, "Ignoring delalloc option - "
                         "requested data journaling mode");
                clear_opt(sbi->s_mount_opt, DELALLOC);
        } else if (test_opt(sb, DELALLOC))
                ext4_msg(sb, KERN_INFO, "delayed allocation enabled");

        err = ext4_setup_system_zone(sb);
        if (err) {
                ext4_msg(sb, KERN_ERR, "failed to initialize system "
                         "zone (%d)\n", err);
                goto failed_mount4;
        }

        ext4_ext_init(sb);
        err = ext4_mb_init(sb, needs_recovery);
        if (err) {
                ext4_msg(sb, KERN_ERR, "failed to initalize mballoc (%d)",
                         err);
                goto failed_mount4;
        }

        sbi->s_kobj.kset = ext4_kset;
        init_completion(&sbi->s_kobj_unregister);
        err = kobject_init_and_add(&sbi->s_kobj, &ext4_ktype, NULL,
                                   "%s", sb->s_id);
        if (err) {
                ext4_mb_release(sb);
                ext4_ext_release(sb);
                goto failed_mount4;
        };

        EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS;
        ext4_orphan_cleanup(sb, es);
        EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS;
        if (needs_recovery) {
                ext4_msg(sb, KERN_INFO, "recovery complete");
                ext4_mark_recovery_complete(sb, es);
        }
        if (EXT4_SB(sb)->s_journal) {
                if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
                        descr = " journalled data mode";
                else if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_ORDERED_DATA)
                        descr = " ordered data mode";
                else
                        descr = " writeback data mode";
        } else
                descr = "out journal";

        ext4_msg(sb, KERN_INFO, "mounted filesystem with%s", descr);

        lock_kernel();
        return 0;

cantfind_ext4:
        if (!silent)
                ext4_msg(sb, KERN_ERR, "VFS: Can't find ext4 filesystem");
        goto failed_mount;

failed_mount4:
        ext4_msg(sb, KERN_ERR, "mount failed");
        ext4_release_system_zone(sb);
        if (sbi->s_journal) {
                jbd2_journal_destroy(sbi->s_journal);
                sbi->s_journal = NULL;
        }
failed_mount3:
        if (sbi->s_flex_groups) {
                if (is_vmalloc_addr(sbi->s_flex_groups))
                        vfree(sbi->s_flex_groups);
                else
                        kfree(sbi->s_flex_groups);
        }
        percpu_counter_destroy(&sbi->s_freeblocks_counter);
        percpu_counter_destroy(&sbi->s_freeinodes_counter);
        percpu_counter_destroy(&sbi->s_dirs_counter);
        percpu_counter_destroy(&sbi->s_dirtyblocks_counter);
failed_mount2:
        for (i = 0; i < db_count; i++)
                brelse(sbi->s_group_desc[i]);
        kfree(sbi->s_group_desc);
failed_mount:
        if (sbi->s_proc) {
                remove_proc_entry(sb->s_id, ext4_proc_root);
        }
#ifdef CONFIG_QUOTA
        for (i = 0; i < MAXQUOTAS; i++)
                kfree(sbi->s_qf_names[i]);
#endif
        ext4_blkdev_remove(sbi);
        brelse(bh);
out_fail:
        sb->s_fs_info = NULL;
        kfree(sbi->s_blockgroup_lock);
        kfree(sbi);
        lock_kernel();
        return ret;
}

/*
 * Setup any per-fs journal parameters now.  We'll do this both on
 * initial mount, once the journal has been initialised but before we've
 * done any recovery; and again on any subsequent remount.
 */
static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
{
        struct ext4_sb_info *sbi = EXT4_SB(sb);

        journal->j_commit_interval = sbi->s_commit_interval;
        journal->j_min_batch_time = sbi->s_min_batch_time;
        journal->j_max_batch_time = sbi->s_max_batch_time;

        spin_lock(&journal->j_state_lock);
        if (test_opt(sb, BARRIER))
                journal->j_flags |= JBD2_BARRIER;
        else
                journal->j_flags &= ~JBD2_BARRIER;
        if (test_opt(sb, DATA_ERR_ABORT))
                journal->j_flags |= JBD2_ABORT_ON_SYNCDATA_ERR;
        else
                journal->j_flags &= ~JBD2_ABORT_ON_SYNCDATA_ERR;
        spin_unlock(&journal->j_state_lock);
}

static journal_t *ext4_get_journal(struct super_block *sb,
                                   unsigned int journal_inum)
{
        struct inode *journal_inode;
        journal_t *journal;

        BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

        /* First, test for the existence of a valid inode on disk.  Bad
         * things happen if we iget() an unused inode, as the subsequent
         * iput() will try to delete it. */

        journal_inode = ext4_iget(sb, journal_inum);
        if (IS_ERR(journal_inode)) {
                ext4_msg(sb, KERN_ERR, "no journal found");
                return NULL;
        }
        if (!journal_inode->i_nlink) {
                make_bad_inode(journal_inode);
                iput(journal_inode);
                ext4_msg(sb, KERN_ERR, "journal inode is deleted");
                return NULL;
        }

        jbd_debug(2, "Journal inode found at %p: %lld bytes\n",
                  journal_inode, journal_inode->i_size);
        if (!S_ISREG(journal_inode->i_mode)) {
                ext4_msg(sb, KERN_ERR, "invalid journal inode");
                iput(journal_inode);
                return NULL;
        }

        journal = jbd2_journal_init_inode(journal_inode);
        if (!journal) {
                ext4_msg(sb, KERN_ERR, "Could not load journal inode");
                iput(journal_inode);
                return NULL;
        }
        journal->j_private = sb;
        ext4_init_journal_params(sb, journal);
        return journal;
}

static journal_t *ext4_get_dev_journal(struct super_block *sb,
                                       dev_t j_dev)
{
        struct buffer_head *bh;
        journal_t *journal;
        ext4_fsblk_t start;
        ext4_fsblk_t len;
        int hblock, blocksize;
        ext4_fsblk_t sb_block;
        unsigned long offset;
        struct ext4_super_block *es;
        struct block_device *bdev;

        BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

        bdev = ext4_blkdev_get(j_dev, sb);
        if (bdev == NULL)
                return NULL;

        if (bd_claim(bdev, sb)) {
                ext4_msg(sb, KERN_ERR,
                        "failed to claim external journal device");
                blkdev_put(bdev, FMODE_READ|FMODE_WRITE);
                return NULL;
        }

        blocksize = sb->s_blocksize;
        hblock = bdev_logical_block_size(bdev);
        if (blocksize < hblock) {
                ext4_msg(sb, KERN_ERR,
                        "blocksize too small for journal device");
                goto out_bdev;
        }

        sb_block = EXT4_MIN_BLOCK_SIZE / blocksize;
        offset = EXT4_MIN_BLOCK_SIZE % blocksize;
        set_blocksize(bdev, blocksize);
        if (!(bh = __bread(bdev, sb_block, blocksize))) {
                ext4_msg(sb, KERN_ERR, "couldn't read superblock of "
                       "external journal");
                goto out_bdev;
        }

        es = (struct ext4_super_block *) (((char *)bh->b_data) + offset);
        if ((le16_to_cpu(es->s_magic) != EXT4_SUPER_MAGIC) ||
            !(le32_to_cpu(es->s_feature_incompat) &
              EXT4_FEATURE_INCOMPAT_JOURNAL_DEV)) {
                ext4_msg(sb, KERN_ERR, "external journal has "
                                        "bad superblock");
                brelse(bh);
                goto out_bdev;
        }

        if (memcmp(EXT4_SB(sb)->s_es->s_journal_uuid, es->s_uuid, 16)) {
                ext4_msg(sb, KERN_ERR, "journal UUID does not match");
                brelse(bh);
                goto out_bdev;
        }

        len = ext4_blocks_count(es);
        start = sb_block + 1;
        brelse(bh);     /* we're done with the superblock */

        journal = jbd2_journal_init_dev(bdev, sb->s_bdev,
                                        start, len, blocksize);
        if (!journal) {
                ext4_msg(sb, KERN_ERR, "failed to create device journal");
                goto out_bdev;
        }
        journal->j_private = sb;
        ll_rw_block(READ, 1, &journal->j_sb_buffer);
        wait_on_buffer(journal->j_sb_buffer);
        if (!buffer_uptodate(journal->j_sb_buffer)) {
                ext4_msg(sb, KERN_ERR, "I/O error on journal device");
                goto out_journal;
        }
        if (be32_to_cpu(journal->j_superblock->s_nr_users) != 1) {
                ext4_msg(sb, KERN_ERR, "External journal has more than one "
                                        "user (unsupported) - %d",
                        be32_to_cpu(journal->j_superblock->s_nr_users));
                goto out_journal;
        }
        EXT4_SB(sb)->journal_bdev = bdev;
        ext4_init_journal_params(sb, journal);
        return journal;

out_journal:
        jbd2_journal_destroy(journal);
out_bdev:
        ext4_blkdev_put(bdev);
        return NULL;
}

static int ext4_load_journal(struct super_block *sb,
                             struct ext4_super_block *es,
                             unsigned long journal_devnum)
{
        journal_t *journal;
        unsigned int journal_inum = le32_to_cpu(es->s_journal_inum);
        dev_t journal_dev;
        int err = 0;
        int really_read_only;

        BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

        if (journal_devnum &&
            journal_devnum != le32_to_cpu(es->s_journal_dev)) {
                ext4_msg(sb, KERN_INFO, "external journal device major/minor "
                        "numbers have changed");
                journal_dev = new_decode_dev(journal_devnum);
        } else
                journal_dev = new_decode_dev(le32_to_cpu(es->s_journal_dev));

        really_read_only = bdev_read_only(sb->s_bdev);

        /*
         * Are we loading a blank journal or performing recovery after a
         * crash?  For recovery, we need to check in advance whether we
         * can get read-write access to the device.
         */
        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER)) {
                if (sb->s_flags & MS_RDONLY) {
                        ext4_msg(sb, KERN_INFO, "INFO: recovery "
                                        "required on readonly filesystem");
                        if (really_read_only) {
                                ext4_msg(sb, KERN_ERR, "write access "
                                        "unavailable, cannot proceed");
                                return -EROFS;
                        }
                        ext4_msg(sb, KERN_INFO, "write access will "
                               "be enabled during recovery");
                }
        }

        if (journal_inum && journal_dev) {
                ext4_msg(sb, KERN_ERR, "filesystem has both journal "
                       "and inode journals!");
                return -EINVAL;
        }

        if (journal_inum) {
                if (!(journal = ext4_get_journal(sb, journal_inum)))
                        return -EINVAL;
        } else {
                if (!(journal = ext4_get_dev_journal(sb, journal_dev)))
                        return -EINVAL;
        }

        if (journal->j_flags & JBD2_BARRIER)
                ext4_msg(sb, KERN_INFO, "barriers enabled");
        else
                ext4_msg(sb, KERN_INFO, "barriers disabled");

        if (!really_read_only && test_opt(sb, UPDATE_JOURNAL)) {
                err = jbd2_journal_update_format(journal);
                if (err)  {
                        ext4_msg(sb, KERN_ERR, "error updating journal");
                        jbd2_journal_destroy(journal);
                        return err;
                }
        }

        if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER))
                err = jbd2_journal_wipe(journal, !really_read_only);
        if (!err)
                err = jbd2_journal_load(journal);

        if (err) {
                ext4_msg(sb, KERN_ERR, "error loading journal");
                jbd2_journal_destroy(journal);
                return err;
        }

        EXT4_SB(sb)->s_journal = journal;
        ext4_clear_journal_err(sb, es);

        if (journal_devnum &&
            journal_devnum != le32_to_cpu(es->s_journal_dev)) {
                es->s_journal_dev = cpu_to_le32(journal_devnum);

                /* Make sure we flush the recovery flag to disk. */
                ext4_commit_super(sb, 1);
        }

        return 0;
}

static int ext4_commit_super(struct super_block *sb, int sync)
{
        struct ext4_super_block *es = EXT4_SB(sb)->s_es;
        struct buffer_head *sbh = EXT4_SB(sb)->s_sbh;
        int error = 0;

        if (!sbh)
                return error;
        if (buffer_write_io_error(sbh)) {
                /*
                 * Oh, dear.  A previous attempt to write the
                 * superblock failed.  This could happen because the
                 * USB device was yanked out.  Or it could happen to
                 * be a transient write error and maybe the block will
                 * be remapped.  Nothing we can do but to retry the
                 * write and hope for the best.
                 */
                ext4_msg(sb, KERN_ERR, "previous I/O error to "
                       "superblock detected");
                clear_buffer_write_io_error(sbh);
                set_buffer_uptodate(sbh);
        }
        es->s_wtime = cpu_to_le32(get_seconds());
        es->s_kbytes_written =
                cpu_to_le64(EXT4_SB(sb)->s_kbytes_written + 
                            ((part_stat_read(sb->s_bdev->bd_part, sectors[1]) -
                              EXT4_SB(sb)->s_sectors_written_start) >> 1));
        ext4_free_blocks_count_set(es, percpu_counter_sum_positive(
                                        &EXT4_SB(sb)->s_freeblocks_counter));
        es->s_free_inodes_count = cpu_to_le32(percpu_counter_sum_positive(
                                        &EXT4_SB(sb)->s_freeinodes_counter));
        sb->s_dirt = 0;
        BUFFER_TRACE(sbh, "marking dirty");
        mark_buffer_dirty(sbh);
        if (sync) {
                error = sync_dirty_buffer(sbh);
                if (error)
                        return error;

                error = buffer_write_io_error(sbh);
                if (error) {
                        ext4_msg(sb, KERN_ERR, "I/O error while writing "
                               "superblock");
                        clear_buffer_write_io_error(sbh);
                        set_buffer_uptodate(sbh);
                }
        }
        return error;
}

/*
 * Have we just finished recovery?  If so, and if we are mounting (or
 * remounting) the filesystem readonly, then we will end up with a
 * consistent fs on disk.  Record that fact.
 */
static void ext4_mark_recovery_complete(struct super_block *sb,
                                        struct ext4_super_block *es)
{
        journal_t *journal = EXT4_SB(sb)->s_journal;

        if (!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
                BUG_ON(journal != NULL);
                return;
        }
        jbd2_journal_lock_updates(journal);
        if (jbd2_journal_flush(journal) < 0)
                goto out;

        if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER) &&
            sb->s_flags & MS_RDONLY) {
                EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
                ext4_commit_super(sb, 1);
        }

out:
        jbd2_journal_unlock_updates(journal);
}

/*
 * If we are mounting (or read-write remounting) a filesystem whose journal
 * has recorded an error from a previous lifetime, move that error to the
 * main filesystem now.
 */
static void ext4_clear_journal_err(struct super_block *sb,
                                   struct ext4_super_block *es)
{
        journal_t *journal;
        int j_errno;
        const char *errstr;

        BUG_ON(!EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL));

        journal = EXT4_SB(sb)->s_journal;

        /*
         * Now check for any error status which may have been recorded in the
         * journal by a prior ext4_error() or ext4_abort()
         */

        j_errno = jbd2_journal_errno(journal);
        if (j_errno) {
                char nbuf[16];

                errstr = ext4_decode_error(sb, j_errno, nbuf);
                ext4_warning(sb, __func__, "Filesystem error recorded "
                             "from previous mount: %s", errstr);
                ext4_warning(sb, __func__, "Marking fs in need of "
                             "filesystem check.");

                EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
                es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
                ext4_commit_super(sb, 1);

                jbd2_journal_clear_err(journal);
        }
}

/*
 * Force the running and committing transactions to commit,
 * and wait on the commit.
 */
int ext4_force_commit(struct super_block *sb)
{
        journal_t *journal;
        int ret = 0;

        if (sb->s_flags & MS_RDONLY)
                return 0;

        journal = EXT4_SB(sb)->s_journal;
        if (journal)
                ret = ext4_journal_force_commit(journal);

        return ret;
}

static void ext4_write_super(struct super_block *sb)
{
        lock_super(sb);
        ext4_commit_super(sb, 1);
        unlock_super(sb);
}

static int ext4_sync_fs(struct super_block *sb, int wait)
{
        int ret = 0;
        tid_t target;

        trace_ext4_sync_fs(sb, wait);
        if (jbd2_journal_start_commit(EXT4_SB(sb)->s_journal, &target)) {
                if (wait)
                        jbd2_log_wait_commit(EXT4_SB(sb)->s_journal, target);
        }
        return ret;
}

/*
 * LVM calls this function before a (read-only) snapshot is created.  This
 * gives us a chance to flush the journal completely and mark the fs clean.
 */
static int ext4_freeze(struct super_block *sb)
{
        int error = 0;
        journal_t *journal;

        if (sb->s_flags & MS_RDONLY)
                return 0;

        journal = EXT4_SB(sb)->s_journal;

        /* Now we set up the journal barrier. */
        jbd2_journal_lock_updates(journal);

        /*
         * Don't clear the needs_recovery flag if we failed to flush
         * the journal.
         */
        error = jbd2_journal_flush(journal);
        if (error < 0) {
        out:
                jbd2_journal_unlock_updates(journal);
                return error;
        }

        /* Journal blocked and flushed, clear needs_recovery flag. */
        EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
        error = ext4_commit_super(sb, 1);
        if (error)
                goto out;
        return 0;
}

/*
 * Called by LVM after the snapshot is done.  We need to reset the RECOVER
 * flag here, even though the filesystem is not technically dirty yet.
 */
static int ext4_unfreeze(struct super_block *sb)
{
        if (sb->s_flags & MS_RDONLY)
                return 0;

        lock_super(sb);
        /* Reset the needs_recovery flag before the fs is unlocked. */
        EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
        ext4_commit_super(sb, 1);
        unlock_super(sb);
        jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
        return 0;
}

static int ext4_remount(struct super_block *sb, int *flags, char *data)
{
        struct ext4_super_block *es;
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        ext4_fsblk_t n_blocks_count = 0;
        unsigned long old_sb_flags;
        struct ext4_mount_options old_opts;
        ext4_group_t g;
        unsigned int journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
        int err;
#ifdef CONFIG_QUOTA
        int i;
#endif

        lock_kernel();

        /* Store the original options */
        lock_super(sb);
        old_sb_flags = sb->s_flags;
        old_opts.s_mount_opt = sbi->s_mount_opt;
        old_opts.s_resuid = sbi->s_resuid;
        old_opts.s_resgid = sbi->s_resgid;
        old_opts.s_commit_interval = sbi->s_commit_interval;
        old_opts.s_min_batch_time = sbi->s_min_batch_time;
        old_opts.s_max_batch_time = sbi->s_max_batch_time;
#ifdef CONFIG_QUOTA
        old_opts.s_jquota_fmt = sbi->s_jquota_fmt;
        for (i = 0; i < MAXQUOTAS; i++)
                old_opts.s_qf_names[i] = sbi->s_qf_names[i];
#endif
        if (sbi->s_journal && sbi->s_journal->j_task->io_context)
                journal_ioprio = sbi->s_journal->j_task->io_context->ioprio;

        /*
         * Allow the "check" option to be passed as a remount option.
         */
        if (!parse_options(data, sb, NULL, &journal_ioprio,
                           &n_blocks_count, 1)) {
                err = -EINVAL;
                goto restore_opts;
        }

        if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
                ext4_abort(sb, __func__, "Abort forced by user");

        sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
                ((sbi->s_mount_opt & EXT4_MOUNT_POSIX_ACL) ? MS_POSIXACL : 0);

        es = sbi->s_es;

        if (sbi->s_journal) {
                ext4_init_journal_params(sb, sbi->s_journal);
                set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);
        }

        if ((*flags & MS_RDONLY) != (sb->s_flags & MS_RDONLY) ||
                n_blocks_count > ext4_blocks_count(es)) {
                if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) {
                        err = -EROFS;
                        goto restore_opts;
                }

                if (*flags & MS_RDONLY) {
                        /*
                         * First of all, the unconditional stuff we have to do
                         * to disable replay of the journal when we next remount
                         */
                        sb->s_flags |= MS_RDONLY;

                        /*
                         * OK, test if we are remounting a valid rw partition
                         * readonly, and if so set the rdonly flag and then
                         * mark the partition as valid again.
                         */
                        if (!(es->s_state & cpu_to_le16(EXT4_VALID_FS)) &&
                            (sbi->s_mount_state & EXT4_VALID_FS))
                                es->s_state = cpu_to_le16(sbi->s_mount_state);

                        if (sbi->s_journal)
                                ext4_mark_recovery_complete(sb, es);
                } else {
                        /* Make sure we can mount this feature set readwrite */
                        if (!ext4_feature_set_ok(sb, 0)) {
                                err = -EROFS;
                                goto restore_opts;
                        }
                        /*
                         * Make sure the group descriptor checksums
                         * are sane.  If they aren't, refuse to remount r/w.
                         */
                        for (g = 0; g < sbi->s_groups_count; g++) {
                                struct ext4_group_desc *gdp =
                                        ext4_get_group_desc(sb, g, NULL);

                                if (!ext4_group_desc_csum_verify(sbi, g, gdp)) {
                                        ext4_msg(sb, KERN_ERR,
               "ext4_remount: Checksum for group %u failed (%u!=%u)",
                g, le16_to_cpu(ext4_group_desc_csum(sbi, g, gdp)),
                                               le16_to_cpu(gdp->bg_checksum));
                                        err = -EINVAL;
                                        goto restore_opts;
                                }
                        }

                        /*
                         * If we have an unprocessed orphan list hanging
                         * around from a previously readonly bdev mount,
                         * require a full umount/remount for now.
                         */
                        if (es->s_last_orphan) {
                                ext4_msg(sb, KERN_WARNING, "Couldn't "
                                       "remount RDWR because of unprocessed "
                                       "orphan inode list.  Please "
                                       "umount/remount instead");
                                err = -EINVAL;
                                goto restore_opts;
                        }

                        /*
                         * Mounting a RDONLY partition read-write, so reread
                         * and store the current valid flag.  (It may have
                         * been changed by e2fsck since we originally mounted
                         * the partition.)
                         */
                        if (sbi->s_journal)
                                ext4_clear_journal_err(sb, es);
                        sbi->s_mount_state = le16_to_cpu(es->s_state);
                        if ((err = ext4_group_extend(sb, es, n_blocks_count)))
                                goto restore_opts;
                        if (!ext4_setup_super(sb, es, 0))
                                sb->s_flags &= ~MS_RDONLY;
                }
        }
        ext4_setup_system_zone(sb);
        if (sbi->s_journal == NULL)
                ext4_commit_super(sb, 1);

#ifdef CONFIG_QUOTA
        /* Release old quota file names */
        for (i = 0; i < MAXQUOTAS; i++)
                if (old_opts.s_qf_names[i] &&
                    old_opts.s_qf_names[i] != sbi->s_qf_names[i])
                        kfree(old_opts.s_qf_names[i]);
#endif
        unlock_super(sb);
        unlock_kernel();
        return 0;

restore_opts:
        sb->s_flags = old_sb_flags;
        sbi->s_mount_opt = old_opts.s_mount_opt;
        sbi->s_resuid = old_opts.s_resuid;
        sbi->s_resgid = old_opts.s_resgid;
        sbi->s_commit_interval = old_opts.s_commit_interval;
        sbi->s_min_batch_time = old_opts.s_min_batch_time;
        sbi->s_max_batch_time = old_opts.s_max_batch_time;
#ifdef CONFIG_QUOTA
        sbi->s_jquota_fmt = old_opts.s_jquota_fmt;
        for (i = 0; i < MAXQUOTAS; i++) {
                if (sbi->s_qf_names[i] &&
                    old_opts.s_qf_names[i] != sbi->s_qf_names[i])
                        kfree(sbi->s_qf_names[i]);
                sbi->s_qf_names[i] = old_opts.s_qf_names[i];
        }
#endif
        unlock_super(sb);
        unlock_kernel();
        return err;
}

static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
{
        struct super_block *sb = dentry->d_sb;
        struct ext4_sb_info *sbi = EXT4_SB(sb);
        struct ext4_super_block *es = sbi->s_es;
        u64 fsid;

        if (test_opt(sb, MINIX_DF)) {
                sbi->s_overhead_last = 0;
        } else if (sbi->s_blocks_last != ext4_blocks_count(es)) {
                ext4_group_t i, ngroups = ext4_get_groups_count(sb);
                ext4_fsblk_t overhead = 0;

                /*
                 * Compute the overhead (FS structures).  This is constant
                 * for a given filesystem unless the number of block groups
                 * changes so we cache the previous value until it does.
                 */

                /*
                 * All of the blocks before first_data_block are
                 * overhead
                 */
                overhead = le32_to_cpu(es->s_first_data_block);

                /*
                 * Add the overhead attributed to the superblock and
                 * block group descriptors.  If the sparse superblocks
                 * feature is turned on, then not all groups have this.
                 */
                for (i = 0; i < ngroups; i++) {
                        overhead += ext4_bg_has_super(sb, i) +
                                ext4_bg_num_gdb(sb, i);
                        cond_resched();
                }

                /*
                 * Every block group has an inode bitmap, a block
                 * bitmap, and an inode table.
                 */
                overhead += ngroups * (2 + sbi->s_itb_per_group);
                sbi->s_overhead_last = overhead;
                smp_wmb();
                sbi->s_blocks_last = ext4_blocks_count(es);
        }

        buf->f_type = EXT4_SUPER_MAGIC;
        buf->f_bsize = sb->s_blocksize;
        buf->f_blocks = ext4_blocks_count(es) - sbi->s_overhead_last;
        buf->f_bfree = percpu_counter_sum_positive(&sbi->s_freeblocks_counter) -
                       percpu_counter_sum_positive(&sbi->s_dirtyblocks_counter);
        ext4_free_blocks_count_set(es, buf->f_bfree);
        buf->f_bavail = buf->f_bfree - ext4_r_blocks_count(es);
        if (buf->f_bfree < ext4_r_blocks_count(es))
                buf->f_bavail = 0;
        buf->f_files = le32_to_cpu(es->s_inodes_count);
        buf->f_ffree = percpu_counter_sum_positive(&sbi->s_freeinodes_counter);
        es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
        buf->f_namelen = EXT4_NAME_LEN;
        fsid = le64_to_cpup((void *)es->s_uuid) ^
               le64_to_cpup((void *)es->s_uuid + sizeof(u64));
        buf->f_fsid.val[0] = fsid & 0xFFFFFFFFUL;
        buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;

        return 0;
}

/* Helper function for writing quotas on sync - we need to start transaction
 * before quota file is locked for write. Otherwise the are possible deadlocks:
 * Process 1                         Process 2
 * ext4_create()                     quota_sync()
 *   jbd2_journal_start()                  write_dquot()
 *   vfs_dq_init()                         down(dqio_mutex)
 *     down(dqio_mutex)                    jbd2_journal_start()
 *
 */

#ifdef CONFIG_QUOTA

static inline struct inode *dquot_to_inode(struct dquot *dquot)
{
        return sb_dqopt(dquot->dq_sb)->files[dquot->dq_type];
}

static int ext4_write_dquot(struct dquot *dquot)
{
        int ret, err;
        handle_t *handle;
        struct inode *inode;

        inode = dquot_to_inode(dquot);
        handle = ext4_journal_start(inode,
                                    EXT4_QUOTA_TRANS_BLOCKS(dquot->dq_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);
        ret = dquot_commit(dquot);
        err = ext4_journal_stop(handle);
        if (!ret)
                ret = err;
        return ret;
}

static int ext4_acquire_dquot(struct dquot *dquot)
{
        int ret, err;
        handle_t *handle;

        handle = ext4_journal_start(dquot_to_inode(dquot),
                                    EXT4_QUOTA_INIT_BLOCKS(dquot->dq_sb));
        if (IS_ERR(handle))
                return PTR_ERR(handle);
        ret = dquot_acquire(dquot);
        err = ext4_journal_stop(handle);
        if (!ret)
                ret = err;
        return ret;
}

static int ext4_release_dquot(struct dquot *dquot)
{
        int ret, err;
        handle_t *handle;

        handle = ext4_journal_start(dquot_to_inode(dquot),
                                    EXT4_QUOTA_DEL_BLOCKS(dquot->dq_sb));
        if (IS_ERR(handle)) {
                /* Release dquot anyway to avoid endless cycle in dqput() */
                dquot_release(dquot);
                return PTR_ERR(handle);
        }
        ret = dquot_release(dquot);
        err = ext4_journal_stop(handle);
        if (!ret)
                ret = err;
        return ret;
}

static int ext4_mark_dquot_dirty(struct dquot *dquot)
{
        /* Are we journaling quotas? */
        if (EXT4_SB(dquot->dq_sb)->s_qf_names[USRQUOTA] ||
            EXT4_SB(dquot->dq_sb)->s_qf_names[GRPQUOTA]) {
                dquot_mark_dquot_dirty(dquot);
                return ext4_write_dquot(dquot);
        } else {
                return dquot_mark_dquot_dirty(dquot);
        }
}

static int ext4_write_info(struct super_block *sb, int type)
{
        int ret, err;
        handle_t *handle;

        /* Data block + inode block */
        handle = ext4_journal_start(sb->s_root->d_inode, 2);
        if (IS_ERR(handle))
                return PTR_ERR(handle);
        ret = dquot_commit_info(sb, type);
        err = ext4_journal_stop(handle);
        if (!ret)
                ret = err;
        return ret;
}

/*
 * Turn on quotas during mount time - we need to find
 * the quota file and such...
 */
static int ext4_quota_on_mount(struct super_block *sb, int type)
{
        return vfs_quota_on_mount(sb, EXT4_SB(sb)->s_qf_names[type],
                                  EXT4_SB(sb)->s_jquota_fmt, type);
}

/*
 * Standard function to be called on quota_on
 */
static int ext4_quota_on(struct super_block *sb, int type, int format_id,
                         char *name, int remount)
{
        int err;
        struct path path;

        if (!test_opt(sb, QUOTA))
                return -EINVAL;
        /* When remounting, no checks are needed and in fact, name is NULL */
        if (remount)
                return vfs_quota_on(sb, type, format_id, name, remount);

        err = kern_path(name, LOOKUP_FOLLOW, &path);
        if (err)
                return err;

        /* Quotafile not on the same filesystem? */
        if (path.mnt->mnt_sb != sb) {
                path_put(&path);
                return -EXDEV;
        }
        /* Journaling quota? */
        if (EXT4_SB(sb)->s_qf_names[type]) {
                /* Quotafile not in fs root? */
                if (path.dentry->d_parent != sb->s_root)
                        ext4_msg(sb, KERN_WARNING,
                                "Quota file not on filesystem root. "
                                "Journaled quota will not work");
        }

        /*
         * When we journal data on quota file, we have to flush journal to see
         * all updates to the file when we bypass pagecache...
         */
        if (EXT4_SB(sb)->s_journal &&
            ext4_should_journal_data(path.dentry->d_inode)) {
                /*
                 * We don't need to lock updates but journal_flush() could
                 * otherwise be livelocked...
                 */
                jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
                err = jbd2_journal_flush(EXT4_SB(sb)->s_journal);
                jbd2_journal_unlock_updates(EXT4_SB(sb)->s_journal);
                if (err) {
                        path_put(&path);
                        return err;
                }
        }

        err = vfs_quota_on_path(sb, type, format_id, &path);
        path_put(&path);
        return err;
}

/* Read data from quotafile - avoid pagecache and such because we cannot afford
 * acquiring the locks... As quota files are never truncated and quota code
 * itself serializes the operations (and noone else should touch the files)
 * we don't have to be afraid of races */
static ssize_t ext4_quota_read(struct super_block *sb, int type, char *data,
                               size_t len, loff_t off)
{
        struct inode *inode = sb_dqopt(sb)->files[type];
        ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
        int err = 0;
        int offset = off & (sb->s_blocksize - 1);
        int tocopy;
        size_t toread;
        struct buffer_head *bh;
        loff_t i_size = i_size_read(inode);

        if (off > i_size)
                return 0;
        if (off+len > i_size)
                len = i_size-off;
        toread = len;
        while (toread > 0) {
                tocopy = sb->s_blocksize - offset < toread ?
                                sb->s_blocksize - offset : toread;
                bh = ext4_bread(NULL, inode, blk, 0, &err);
                if (err)
                        return err;
                if (!bh)        /* A hole? */
                        memset(data, 0, tocopy);
                else
                        memcpy(data, bh->b_data+offset, tocopy);
                brelse(bh);
                offset = 0;
                toread -= tocopy;
                data += tocopy;
                blk++;
        }
        return len;
}

/* Write to quotafile (we know the transaction is already started and has
 * enough credits) */
static ssize_t ext4_quota_write(struct super_block *sb, int type,
                                const char *data, size_t len, loff_t off)
{
        struct inode *inode = sb_dqopt(sb)->files[type];
        ext4_lblk_t blk = off >> EXT4_BLOCK_SIZE_BITS(sb);
        int err = 0;
        int offset = off & (sb->s_blocksize - 1);
        int tocopy;
        int journal_quota = EXT4_SB(sb)->s_qf_names[type] != NULL;
        size_t towrite = len;
        struct buffer_head *bh;
        handle_t *handle = journal_current_handle();

        if (EXT4_SB(sb)->s_journal && !handle) {
                ext4_msg(sb, KERN_WARNING, "Quota write (off=%llu, len=%llu)"
                        " cancelled because transaction is not started",
                        (unsigned long long)off, (unsigned long long)len);
                return -EIO;
        }
        mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
        while (towrite > 0) {
                tocopy = sb->s_blocksize - offset < towrite ?
                                sb->s_blocksize - offset : towrite;
                bh = ext4_bread(handle, inode, blk, 1, &err);
                if (!bh)
                        goto out;
                if (journal_quota) {
                        err = ext4_journal_get_write_access(handle, bh);
                        if (err) {
                                brelse(bh);
                                goto out;
                        }
                }
                lock_buffer(bh);
                memcpy(bh->b_data+offset, data, tocopy);
                flush_dcache_page(bh->b_page);
                unlock_buffer(bh);
                if (journal_quota)
                        err = ext4_handle_dirty_metadata(handle, NULL, bh);
                else {
                        /* Always do at least ordered writes for quotas */
                        err = ext4_jbd2_file_inode(handle, inode);
                        mark_buffer_dirty(bh);
                }
                brelse(bh);
                if (err)
                        goto out;
                offset = 0;
                towrite -= tocopy;
                data += tocopy;
                blk++;
        }
out:
        if (len == towrite) {
                mutex_unlock(&inode->i_mutex);
                return err;
        }
        if (inode->i_size < off+len-towrite) {
                i_size_write(inode, off+len-towrite);
                EXT4_I(inode)->i_disksize = inode->i_size;
        }
        inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        ext4_mark_inode_dirty(handle, inode);
        mutex_unlock(&inode->i_mutex);
        return len - towrite;
}

#endif

static int ext4_get_sb(struct file_system_type *fs_type, int flags,
                       const char *dev_name, void *data, struct vfsmount *mnt)
{
        return get_sb_bdev(fs_type, flags, dev_name, data, ext4_fill_super,mnt);
}

static struct file_system_type ext4_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "ext4",
        .get_sb         = ext4_get_sb,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};

#ifdef CONFIG_EXT4DEV_COMPAT
static int ext4dev_get_sb(struct file_system_type *fs_type, int flags,
                          const char *dev_name, void *data,struct vfsmount *mnt)
{
        printk(KERN_WARNING "EXT4-fs (%s): Update your userspace programs "
               "to mount using ext4\n", dev_name);
        printk(KERN_WARNING "EXT4-fs (%s): ext4dev backwards compatibility "
               "will go away by 2.6.31\n", dev_name);
        return get_sb_bdev(fs_type, flags, dev_name, data, ext4_fill_super,mnt);
}

static struct file_system_type ext4dev_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "ext4dev",
        .get_sb         = ext4dev_get_sb,
        .kill_sb        = kill_block_super,
        .fs_flags       = FS_REQUIRES_DEV,
};
MODULE_ALIAS("ext4dev");
#endif

static int __init init_ext4_fs(void)
{
        int err;

        err = init_ext4_system_zone();
        if (err)
                return err;
        ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj);
        if (!ext4_kset)
                goto out4;
        ext4_proc_root = proc_mkdir("fs/ext4", NULL);
        err = init_ext4_mballoc();
        if (err)
                goto out3;

        err = init_ext4_xattr();
        if (err)
                goto out2;
        err = init_inodecache();
        if (err)
                goto out1;
        err = register_filesystem(&ext4_fs_type);
        if (err)
                goto out;
#ifdef CONFIG_EXT4DEV_COMPAT
        err = register_filesystem(&ext4dev_fs_type);
        if (err) {
                unregister_filesystem(&ext4_fs_type);
                goto out;
        }
#endif
        return 0;
out:
        destroy_inodecache();
out1:
        exit_ext4_xattr();
out2:
        exit_ext4_mballoc();
out3:
        remove_proc_entry("fs/ext4", NULL);
        kset_unregister(ext4_kset);
out4:
        exit_ext4_system_zone();
        return err;
}

static void __exit exit_ext4_fs(void)
{
        unregister_filesystem(&ext4_fs_type);
#ifdef CONFIG_EXT4DEV_COMPAT
        unregister_filesystem(&ext4dev_fs_type);
#endif
        destroy_inodecache();
        exit_ext4_xattr();
        exit_ext4_mballoc();
        remove_proc_entry("fs/ext4", NULL);
        kset_unregister(ext4_kset);
        exit_ext4_system_zone();
}

MODULE_AUTHOR("Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others");
MODULE_DESCRIPTION("Fourth Extended Filesystem");
MODULE_LICENSE("GPL");
module_init(init_ext4_fs)
module_exit(exit_ext4_fs)