Btrfs: cleanup extent_clear_unlock_delalloc flags
[safe/jmp/linux-2.6] / fs / fs-writeback.c
index 30d9383..c54226b 100644 (file)
@@ -8,7 +8,7 @@
  * pages against inodes.  ie: data writeback.  Writeout of the
  * inode itself is not handled here.
  *
- * 10Apr2002   akpm@zip.com.au
+ * 10Apr2002   Andrew Morton
  *             Split out of fs/inode.c
  *             Additions for address_space-based writeback
  */
 #include <linux/buffer_head.h>
 #include "internal.h"
 
+
+/**
+ * writeback_acquire - attempt to get exclusive writeback access to a device
+ * @bdi: the device's backing_dev_info structure
+ *
+ * It is a waste of resources to have more than one pdflush thread blocked on
+ * a single request queue.  Exclusion at the request_queue level is obtained
+ * via a flag in the request_queue's backing_dev_info.state.
+ *
+ * Non-request_queue-backed address_spaces will share default_backing_dev_info,
+ * unless they implement their own.  Which is somewhat inefficient, as this
+ * may prevent concurrent writeback against multiple devices.
+ */
+static int writeback_acquire(struct backing_dev_info *bdi)
+{
+       return !test_and_set_bit(BDI_pdflush, &bdi->state);
+}
+
+/**
+ * writeback_in_progress - determine whether there is writeback in progress
+ * @bdi: the device's backing_dev_info structure.
+ *
+ * Determine whether there is writeback in progress against a backing device.
+ */
+int writeback_in_progress(struct backing_dev_info *bdi)
+{
+       return test_bit(BDI_pdflush, &bdi->state);
+}
+
+/**
+ * writeback_release - relinquish exclusive writeback access against a device.
+ * @bdi: the device's backing_dev_info structure
+ */
+static void writeback_release(struct backing_dev_info *bdi)
+{
+       BUG_ON(!writeback_in_progress(bdi));
+       clear_bit(BDI_pdflush, &bdi->state);
+}
+
+static noinline void block_dump___mark_inode_dirty(struct inode *inode)
+{
+       if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
+               struct dentry *dentry;
+               const char *name = "?";
+
+               dentry = d_find_alias(inode);
+               if (dentry) {
+                       spin_lock(&dentry->d_lock);
+                       name = (const char *) dentry->d_name.name;
+               }
+               printk(KERN_DEBUG
+                      "%s(%d): dirtied inode %lu (%s) on %s\n",
+                      current->comm, task_pid_nr(current), inode->i_ino,
+                      name, inode->i_sb->s_id);
+               if (dentry) {
+                       spin_unlock(&dentry->d_lock);
+                       dput(dentry);
+               }
+       }
+}
+
 /**
  *     __mark_inode_dirty -    internal function
  *     @inode: inode to mark
@@ -75,23 +136,8 @@ void __mark_inode_dirty(struct inode *inode, int flags)
        if ((inode->i_state & flags) == flags)
                return;
 
-       if (unlikely(block_dump)) {
-               struct dentry *dentry = NULL;
-               const char *name = "?";
-
-               if (!list_empty(&inode->i_dentry)) {
-                       dentry = list_entry(inode->i_dentry.next,
-                                           struct dentry, d_alias);
-                       if (dentry && dentry->d_name.name)
-                               name = (const char *) dentry->d_name.name;
-               }
-
-               if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev"))
-                       printk(KERN_DEBUG
-                              "%s(%d): dirtied inode %lu (%s) on %s\n",
-                              current->comm, current->pid, inode->i_ino,
-                              name, inode->i_sb->s_id);
-       }
+       if (unlikely(block_dump))
+               block_dump___mark_inode_dirty(inode);
 
        spin_lock(&inode_lock);
        if ((inode->i_state & flags) != flags) {
@@ -100,11 +146,11 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                inode->i_state |= flags;
 
                /*
-                * If the inode is locked, just update its dirty state. 
+                * If the inode is being synced, just update its dirty state.
                 * The unlocker will place the inode on the appropriate
                 * superblock list, based upon its state.
                 */
-               if (inode->i_state & I_LOCK)
+               if (inode->i_state & I_SYNC)
                        goto out;
 
                /*
@@ -119,7 +165,7 @@ void __mark_inode_dirty(struct inode *inode, int flags)
                        goto out;
 
                /*
-                * If the inode was already on s_dirty or s_io, don't
+                * If the inode was already on s_dirty/s_io/s_more_io, don't
                 * reposition it (that would break s_dirty time-ordering).
                 */
                if (!was_dirty) {
@@ -157,7 +203,7 @@ static void redirty_tail(struct inode *inode)
                struct inode *tail_inode;
 
                tail_inode = list_entry(sb->s_dirty.next, struct inode, i_list);
-               if (!time_after_eq(inode->dirtied_when,
+               if (time_before(inode->dirtied_when,
                                tail_inode->dirtied_when))
                        inode->dirtied_when = jiffies;
        }
@@ -165,29 +211,93 @@ static void redirty_tail(struct inode *inode)
 }
 
 /*
- * Redirty an inode, but mark it as the very next-to-be-written inode on its
- * superblock's dirty-inode list.
- * We need to preserve s_dirty's reverse-time-orderedness, so we cheat by
- * setting this inode's dirtied_when to the same value as that of the inode
- * which is presently head-of-list, if present head-of-list is newer than this
- * inode. (head-of-list is the least-recently-dirtied inode: the oldest one).
+ * requeue inode for re-scanning after sb->s_io list is exhausted.
  */
-static void redirty_head(struct inode *inode)
+static void requeue_io(struct inode *inode)
 {
-       struct super_block *sb = inode->i_sb;
+       list_move(&inode->i_list, &inode->i_sb->s_more_io);
+}
 
-       if (!list_empty(&sb->s_dirty)) {
-               struct inode *head_inode;
+static void inode_sync_complete(struct inode *inode)
+{
+       /*
+        * Prevent speculative execution through spin_unlock(&inode_lock);
+        */
+       smp_mb();
+       wake_up_bit(&inode->i_state, __I_SYNC);
+}
+
+static bool inode_dirtied_after(struct inode *inode, unsigned long t)
+{
+       bool ret = time_after(inode->dirtied_when, t);
+#ifndef CONFIG_64BIT
+       /*
+        * For inodes being constantly redirtied, dirtied_when can get stuck.
+        * It _appears_ to be in the future, but is actually in distant past.
+        * This test is necessary to prevent such wrapped-around relative times
+        * from permanently stopping the whole pdflush writeback.
+        */
+       ret = ret && time_before_eq(inode->dirtied_when, jiffies);
+#endif
+       return ret;
+}
 
-               head_inode = list_entry(sb->s_dirty.prev, struct inode, i_list);
-               if (time_after(inode->dirtied_when, head_inode->dirtied_when))
-                       inode->dirtied_when = head_inode->dirtied_when;
+/*
+ * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
+ */
+static void move_expired_inodes(struct list_head *delaying_queue,
+                              struct list_head *dispatch_queue,
+                               unsigned long *older_than_this)
+{
+       while (!list_empty(delaying_queue)) {
+               struct inode *inode = list_entry(delaying_queue->prev,
+                                               struct inode, i_list);
+               if (older_than_this &&
+                   inode_dirtied_after(inode, *older_than_this))
+                       break;
+               list_move(&inode->i_list, dispatch_queue);
        }
-       list_move_tail(&inode->i_list, &sb->s_dirty);
 }
 
 /*
- * Write a single inode's dirty pages and inode data out to disk.
+ * Queue all expired dirty inodes for io, eldest first.
+ */
+static void queue_io(struct super_block *sb,
+                               unsigned long *older_than_this)
+{
+       list_splice_init(&sb->s_more_io, sb->s_io.prev);
+       move_expired_inodes(&sb->s_dirty, &sb->s_io, older_than_this);
+}
+
+int sb_has_dirty_inodes(struct super_block *sb)
+{
+       return !list_empty(&sb->s_dirty) ||
+              !list_empty(&sb->s_io) ||
+              !list_empty(&sb->s_more_io);
+}
+EXPORT_SYMBOL(sb_has_dirty_inodes);
+
+/*
+ * Wait for writeback on an inode to complete.
+ */
+static void inode_wait_for_writeback(struct inode *inode)
+{
+       DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
+       wait_queue_head_t *wqh;
+
+       wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
+       do {
+               spin_unlock(&inode_lock);
+               __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
+               spin_lock(&inode_lock);
+       } while (inode->i_state & I_SYNC);
+}
+
+/*
+ * Write out an inode's dirty pages.  Called under inode_lock.  Either the
+ * caller has ref on the inode (either via __iget or via syscall against an fd)
+ * or the inode has I_WILL_FREE set (via generic_forget_inode)
+ *
  * If `wait' is set, wait on the writeout.
  *
  * The whole writeout design is quite complex and fragile.  We want to avoid
@@ -197,18 +307,43 @@ static void redirty_head(struct inode *inode)
  * Called under inode_lock.
  */
 static int
-__sync_single_inode(struct inode *inode, struct writeback_control *wbc)
+writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 {
-       unsigned dirty;
        struct address_space *mapping = inode->i_mapping;
        int wait = wbc->sync_mode == WB_SYNC_ALL;
+       unsigned dirty;
        int ret;
 
-       BUG_ON(inode->i_state & I_LOCK);
+       if (!atomic_read(&inode->i_count))
+               WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
+       else
+               WARN_ON(inode->i_state & I_WILL_FREE);
+
+       if (inode->i_state & I_SYNC) {
+               /*
+                * If this inode is locked for writeback and we are not doing
+                * writeback-for-data-integrity, move it to s_more_io so that
+                * writeback can proceed with the other inodes on s_io.
+                *
+                * We'll have another go at writing back this inode when we
+                * completed a full scan of s_io.
+                */
+               if (!wait) {
+                       requeue_io(inode);
+                       return 0;
+               }
 
-       /* Set I_LOCK, reset I_DIRTY */
+               /*
+                * It's a data-integrity sync.  We must wait.
+                */
+               inode_wait_for_writeback(inode);
+       }
+
+       BUG_ON(inode->i_state & I_SYNC);
+
+       /* Set I_SYNC, reset I_DIRTY */
        dirty = inode->i_state & I_DIRTY;
-       inode->i_state |= I_LOCK;
+       inode->i_state |= I_SYNC;
        inode->i_state &= ~I_DIRTY;
 
        spin_unlock(&inode_lock);
@@ -229,14 +364,14 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
        }
 
        spin_lock(&inode_lock);
-       inode->i_state &= ~I_LOCK;
-       if (!(inode->i_state & I_FREEING)) {
+       inode->i_state &= ~I_SYNC;
+       if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
                if (!(inode->i_state & I_DIRTY) &&
                    mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
                        /*
                         * We didn't write back all the pages.  nfs_writepages()
                         * sometimes bales out without doing anything. Redirty
-                        * the inode.  It is moved from s_io onto s_dirty.
+                        * the inode; Move it from s_io onto s_more_io/s_dirty.
                         */
                        /*
                         * akpm: if the caller was the kupdate function we put
@@ -249,13 +384,22 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
                         */
                        if (wbc->for_kupdate) {
                                /*
-                                * For the kupdate function we leave the inode
-                                * at the head of sb_dirty so it will get more
-                                * writeout as soon as the queue becomes
-                                * uncongested.
+                                * For the kupdate function we move the inode
+                                * to s_more_io so it will get more writeout as
+                                * soon as the queue becomes uncongested.
                                 */
                                inode->i_state |= I_DIRTY_PAGES;
-                               redirty_head(inode);
+                               if (wbc->nr_to_write <= 0) {
+                                       /*
+                                        * slice used up: queue for next turn
+                                        */
+                                       requeue_io(inode);
+                               } else {
+                                       /*
+                                        * somehow blocked: retry later
+                                        */
+                                       redirty_tail(inode);
+                               }
                        } else {
                                /*
                                 * Otherwise fully redirty the inode so that
@@ -285,80 +429,20 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
                        list_move(&inode->i_list, &inode_unused);
                }
        }
-       wake_up_inode(inode);
+       inode_sync_complete(inode);
        return ret;
 }
 
 /*
- * Write out an inode's dirty pages.  Called under inode_lock.  Either the
- * caller has ref on the inode (either via __iget or via syscall against an fd)
- * or the inode has I_WILL_FREE set (via generic_forget_inode)
- */
-static int
-__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
-{
-       wait_queue_head_t *wqh;
-
-       if (!atomic_read(&inode->i_count))
-               WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
-       else
-               WARN_ON(inode->i_state & I_WILL_FREE);
-
-       if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
-               struct address_space *mapping = inode->i_mapping;
-               int ret;
-
-               /*
-                * We're skipping this inode because it's locked, and we're not
-                * doing writeback-for-data-integrity.  Move it to the head of
-                * s_dirty so that writeback can proceed with the other inodes
-                * on s_io.  We'll have another go at writing back this inode
-                * when the s_dirty iodes get moved back onto s_io.
-                */
-               redirty_head(inode);
-
-               /*
-                * Even if we don't actually write the inode itself here,
-                * we can at least start some of the data writeout..
-                */
-               spin_unlock(&inode_lock);
-               ret = do_writepages(mapping, wbc);
-               spin_lock(&inode_lock);
-               return ret;
-       }
-
-       /*
-        * It's a data-integrity sync.  We must wait.
-        */
-       if (inode->i_state & I_LOCK) {
-               DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
-
-               wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
-               do {
-                       spin_unlock(&inode_lock);
-                       __wait_on_bit(wqh, &wq, inode_wait,
-                                                       TASK_UNINTERRUPTIBLE);
-                       spin_lock(&inode_lock);
-               } while (inode->i_state & I_LOCK);
-       }
-       return __sync_single_inode(inode, wbc);
-}
-
-/*
  * Write out a superblock's list of dirty inodes.  A wait will be performed
  * upon no inodes, all inodes or the final one, depending upon sync_mode.
  *
  * If older_than_this is non-NULL, then only write out inodes which
  * had their first dirtying at a time earlier than *older_than_this.
  *
- * If we're a pdlfush thread, then implement pdflush collision avoidance
+ * If we're a pdflush thread, then implement pdflush collision avoidance
  * against the entire list.
  *
- * WB_SYNC_HOLD is a hack for sys_sync(): reattach the inode to sb->s_dirty so
- * that it can be located for waiting on in __writeback_single_inode().
- *
- * Called under inode_lock.
- *
  * If `bdi' is non-zero then we're being asked to writeback a specific queue.
  * This function assumes that the blockdev superblock's inodes are backed by
  * a variety of queues, so all inodes are searched.  For other superblocks,
@@ -372,15 +456,17 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
  * The inodes to be written are parked on sb->s_io.  They are moved back onto
  * sb->s_dirty as they are selected for writing.  This way, none can be missed
  * on the writer throttling path, and we get decent balancing between many
- * throttled threads: we don't want them all piling up on __wait_on_inode.
+ * throttled threads: we don't want them all piling up on inode_sync_wait.
  */
-static void
-sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
+void generic_sync_sb_inodes(struct super_block *sb,
+                               struct writeback_control *wbc)
 {
        const unsigned long start = jiffies;    /* livelock avoidance */
+       int sync = wbc->sync_mode == WB_SYNC_ALL;
 
+       spin_lock(&inode_lock);
        if (!wbc->for_kupdate || list_empty(&sb->s_io))
-               list_splice_init(&sb->s_dirty, &sb->s_io);
+               queue_io(sb, wbc->older_than_this);
 
        while (!list_empty(&sb->s_io)) {
                struct inode *inode = list_entry(sb->s_io.prev,
@@ -406,42 +492,41 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
                        break;
                }
 
+               if (inode->i_state & (I_NEW | I_WILL_FREE)) {
+                       requeue_io(inode);
+                       continue;
+               }
+
                if (wbc->nonblocking && bdi_write_congested(bdi)) {
                        wbc->encountered_congestion = 1;
                        if (!sb_is_blkdev_sb(sb))
                                break;          /* Skip a congested fs */
-                       list_move(&inode->i_list, &sb->s_dirty);
+                       requeue_io(inode);
                        continue;               /* Skip a congested blockdev */
                }
 
                if (wbc->bdi && bdi != wbc->bdi) {
                        if (!sb_is_blkdev_sb(sb))
                                break;          /* fs has the wrong queue */
-                       list_move(&inode->i_list, &sb->s_dirty);
+                       requeue_io(inode);
                        continue;               /* blockdev has wrong queue */
                }
 
-               /* Was this inode dirtied after sync_sb_inodes was called? */
-               if (time_after(inode->dirtied_when, start))
-                       break;
-
-               /* Was this inode dirtied too recently? */
-               if (wbc->older_than_this && time_after(inode->dirtied_when,
-                                               *wbc->older_than_this))
+               /*
+                * Was this inode dirtied after sync_sb_inodes was called?
+                * This keeps sync from extra jobs and livelock.
+                */
+               if (inode_dirtied_after(inode, start))
                        break;
 
                /* Is another pdflush already flushing this queue? */
                if (current_is_pdflush() && !writeback_acquire(bdi))
                        break;
 
-               BUG_ON(inode->i_state & I_FREEING);
+               BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
                __iget(inode);
                pages_skipped = wbc->pages_skipped;
-               __writeback_single_inode(inode, wbc);
-               if (wbc->sync_mode == WB_SYNC_HOLD) {
-                       inode->dirtied_when = jiffies;
-                       list_move(&inode->i_list, &sb->s_dirty);
-               }
+               writeback_single_inode(inode, wbc);
                if (current_is_pdflush())
                        writeback_release(bdi);
                if (wbc->pages_skipped != pages_skipped) {
@@ -455,11 +540,66 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
                iput(inode);
                cond_resched();
                spin_lock(&inode_lock);
-               if (wbc->nr_to_write <= 0)
+               if (wbc->nr_to_write <= 0) {
+                       wbc->more_io = 1;
                        break;
+               }
+               if (!list_empty(&sb->s_more_io))
+                       wbc->more_io = 1;
        }
+
+       if (sync) {
+               struct inode *inode, *old_inode = NULL;
+
+               /*
+                * Data integrity sync. Must wait for all pages under writeback,
+                * because there may have been pages dirtied before our sync
+                * call, but which had writeout started before we write it out.
+                * In which case, the inode may not be on the dirty list, but
+                * we still have to wait for that writeout.
+                */
+               list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+                       struct address_space *mapping;
+
+                       if (inode->i_state &
+                                       (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
+                               continue;
+                       mapping = inode->i_mapping;
+                       if (mapping->nrpages == 0)
+                               continue;
+                       __iget(inode);
+                       spin_unlock(&inode_lock);
+                       /*
+                        * We hold a reference to 'inode' so it couldn't have
+                        * been removed from s_inodes list while we dropped the
+                        * inode_lock.  We cannot iput the inode now as we can
+                        * be holding the last reference and we cannot iput it
+                        * under inode_lock. So we keep the reference and iput
+                        * it later.
+                        */
+                       iput(old_inode);
+                       old_inode = inode;
+
+                       filemap_fdatawait(mapping);
+
+                       cond_resched();
+
+                       spin_lock(&inode_lock);
+               }
+               spin_unlock(&inode_lock);
+               iput(old_inode);
+       } else
+               spin_unlock(&inode_lock);
+
        return;         /* Leave any unwritten inodes on s_io */
 }
+EXPORT_SYMBOL_GPL(generic_sync_sb_inodes);
+
+static void sync_sb_inodes(struct super_block *sb,
+                               struct writeback_control *wbc)
+{
+       generic_sync_sb_inodes(sb, wbc);
+}
 
 /*
  * Start writeback of dirty pagecache data against all unlocked inodes.
@@ -467,7 +607,7 @@ sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
  * Note:
  * We don't need to grab a reference to superblock here. If it has non-empty
  * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
- * past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are
+ * past sync_inodes_sb() until the ->s_dirty/s_io/s_more_io lists are all
  * empty. Since __sync_single_inode() regains inode_lock before it finally moves
  * inode from superblock lists we are OK.
  *
@@ -488,9 +628,8 @@ writeback_inodes(struct writeback_control *wbc)
        might_sleep();
        spin_lock(&sb_lock);
 restart:
-       sb = sb_entry(super_blocks.prev);
-       for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
-               if (!list_empty(&sb->s_dirty) || !list_empty(&sb->s_io)) {
+       list_for_each_entry_reverse(sb, &super_blocks, s_list) {
+               if (sb_has_dirty_inodes(sb)) {
                        /* we're making our own get_super here */
                        sb->s_count++;
                        spin_unlock(&sb_lock);
@@ -500,11 +639,8 @@ restart:
                         * be unmounted by the time it is released.
                         */
                        if (down_read_trylock(&sb->s_umount)) {
-                               if (sb->s_root) {
-                                       spin_lock(&inode_lock);
+                               if (sb->s_root)
                                        sync_sb_inodes(sb, wbc);
-                                       spin_unlock(&inode_lock);
-                               }
                                up_read(&sb->s_umount);
                        }
                        spin_lock(&sb_lock);
@@ -519,8 +655,7 @@ restart:
 
 /*
  * writeback and wait upon the filesystem's dirty inodes.  The caller will
- * do this in two passes - one to write, and one to wait.  WB_SYNC_HOLD is
- * used to park the written inodes on sb->s_dirty for the wait pass.
+ * do this in two passes - one to write, and one to wait.
  *
  * A finite limit is set on the number of pages which will be written.
  * To prevent infinite livelock of sys_sync().
@@ -531,89 +666,21 @@ restart:
 void sync_inodes_sb(struct super_block *sb, int wait)
 {
        struct writeback_control wbc = {
-               .sync_mode      = wait ? WB_SYNC_ALL : WB_SYNC_HOLD,
+               .sync_mode      = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
                .range_start    = 0,
                .range_end      = LLONG_MAX,
        };
-       unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
-       unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
-
-       wbc.nr_to_write = nr_dirty + nr_unstable +
-                       (inodes_stat.nr_inodes - inodes_stat.nr_unused) +
-                       nr_dirty + nr_unstable;
-       wbc.nr_to_write += wbc.nr_to_write / 2;         /* Bit more for luck */
-       spin_lock(&inode_lock);
-       sync_sb_inodes(sb, &wbc);
-       spin_unlock(&inode_lock);
-}
-
-/*
- * Rather lame livelock avoidance.
- */
-static void set_sb_syncing(int val)
-{
-       struct super_block *sb;
-       spin_lock(&sb_lock);
-       sb = sb_entry(super_blocks.prev);
-       for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
-               sb->s_syncing = val;
-       }
-       spin_unlock(&sb_lock);
-}
-
-/**
- * sync_inodes - writes all inodes to disk
- * @wait: wait for completion
- *
- * sync_inodes() goes through each super block's dirty inode list, writes the
- * inodes out, waits on the writeout and puts the inodes back on the normal
- * list.
- *
- * This is for sys_sync().  fsync_dev() uses the same algorithm.  The subtle
- * part of the sync functions is that the blockdev "superblock" is processed
- * last.  This is because the write_inode() function of a typical fs will
- * perform no I/O, but will mark buffers in the blockdev mapping as dirty.
- * What we want to do is to perform all that dirtying first, and then write
- * back all those inode blocks via the blockdev mapping in one sweep.  So the
- * additional (somewhat redundant) sync_blockdev() calls here are to make
- * sure that really happens.  Because if we call sync_inodes_sb(wait=1) with
- * outstanding dirty inodes, the writeback goes block-at-a-time within the
- * filesystem's write_inode().  This is extremely slow.
- */
-static void __sync_inodes(int wait)
-{
-       struct super_block *sb;
 
-       spin_lock(&sb_lock);
-restart:
-       list_for_each_entry(sb, &super_blocks, s_list) {
-               if (sb->s_syncing)
-                       continue;
-               sb->s_syncing = 1;
-               sb->s_count++;
-               spin_unlock(&sb_lock);
-               down_read(&sb->s_umount);
-               if (sb->s_root) {
-                       sync_inodes_sb(sb, wait);
-                       sync_blockdev(sb->s_bdev);
-               }
-               up_read(&sb->s_umount);
-               spin_lock(&sb_lock);
-               if (__put_super_and_need_restart(sb))
-                       goto restart;
-       }
-       spin_unlock(&sb_lock);
-}
+       if (!wait) {
+               unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
+               unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
 
-void sync_inodes(int wait)
-{
-       set_sb_syncing(0);
-       __sync_inodes(0);
+               wbc.nr_to_write = nr_dirty + nr_unstable +
+                       (inodes_stat.nr_inodes - inodes_stat.nr_unused);
+       } else
+               wbc.nr_to_write = LONG_MAX; /* doesn't actually matter */
 
-       if (wait) {
-               set_sb_syncing(0);
-               __sync_inodes(1);
-       }
+       sync_sb_inodes(sb, &wbc);
 }
 
 /**
@@ -631,7 +698,7 @@ int write_inode_now(struct inode *inode, int sync)
        int ret;
        struct writeback_control wbc = {
                .nr_to_write = LONG_MAX,
-               .sync_mode = WB_SYNC_ALL,
+               .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
                .range_start = 0,
                .range_end = LLONG_MAX,
        };
@@ -641,10 +708,10 @@ int write_inode_now(struct inode *inode, int sync)
 
        might_sleep();
        spin_lock(&inode_lock);
-       ret = __writeback_single_inode(inode, &wbc);
+       ret = writeback_single_inode(inode, &wbc);
        spin_unlock(&inode_lock);
        if (sync)
-               wait_on_inode(inode);
+               inode_sync_wait(inode);
        return ret;
 }
 EXPORT_SYMBOL(write_inode_now);
@@ -665,7 +732,7 @@ int sync_inode(struct inode *inode, struct writeback_control *wbc)
        int ret;
 
        spin_lock(&inode_lock);
-       ret = __writeback_single_inode(inode, wbc);
+       ret = writeback_single_inode(inode, wbc);
        spin_unlock(&inode_lock);
        return ret;
 }
@@ -719,47 +786,8 @@ int generic_osync_inode(struct inode *inode, struct address_space *mapping, int
                        err = err2;
        }
        else
-               wait_on_inode(inode);
+               inode_sync_wait(inode);
 
        return err;
 }
-
 EXPORT_SYMBOL(generic_osync_inode);
-
-/**
- * writeback_acquire: attempt to get exclusive writeback access to a device
- * @bdi: the device's backing_dev_info structure
- *
- * It is a waste of resources to have more than one pdflush thread blocked on
- * a single request queue.  Exclusion at the request_queue level is obtained
- * via a flag in the request_queue's backing_dev_info.state.
- *
- * Non-request_queue-backed address_spaces will share default_backing_dev_info,
- * unless they implement their own.  Which is somewhat inefficient, as this
- * may prevent concurrent writeback against multiple devices.
- */
-int writeback_acquire(struct backing_dev_info *bdi)
-{
-       return !test_and_set_bit(BDI_pdflush, &bdi->state);
-}
-
-/**
- * writeback_in_progress: determine whether there is writeback in progress
- * @bdi: the device's backing_dev_info structure.
- *
- * Determine whether there is writeback in progress against a backing device.
- */
-int writeback_in_progress(struct backing_dev_info *bdi)
-{
-       return test_bit(BDI_pdflush, &bdi->state);
-}
-
-/**
- * writeback_release: relinquish exclusive writeback access against a device.
- * @bdi: the device's backing_dev_info structure
- */
-void writeback_release(struct backing_dev_info *bdi)
-{
-       BUG_ON(!writeback_in_progress(bdi));
-       clear_bit(BDI_pdflush, &bdi->state);
-}