X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fsuper.c;h=69688b15f1fa928002584b1504cfe2146ba3b67f;hb=0e3c9a2284f5417f196e327c254d0b84c9ee8929;hp=bc734f8b3e18678189e6fa71205390d3546840c2;hpb=b20bd1a5e78af267dc4b6e1ffed48d5d776302c5;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/super.c b/fs/super.c index bc734f8..69688b1 100644 --- a/fs/super.c +++ b/fs/super.c @@ -22,23 +22,15 @@ #include #include -#include -#include #include #include #include -#include #include #include -#include -#include #include /* for the emergency remount stuff */ #include -#include #include -#include #include -#include #include "internal.h" @@ -96,6 +88,7 @@ static struct super_block *alloc_super(struct file_system_type *type) s->s_count = 1; atomic_set(&s->s_active, 1); mutex_init(&s->s_vfs_rename_mutex); + lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key); mutex_init(&s->s_dquot.dqio_mutex); mutex_init(&s->s_dquot.dqonoff_mutex); init_rwsem(&s->s_dquot.dqptr_sem); @@ -127,39 +120,14 @@ static inline void destroy_super(struct super_block *s) /* Superblock refcounting */ /* - * Drop a superblock's refcount. Returns non-zero if the superblock was - * destroyed. The caller must hold sb_lock. + * Drop a superblock's refcount. The caller must hold sb_lock. */ -static int __put_super(struct super_block *sb) +void __put_super(struct super_block *sb) { - int ret = 0; - if (!--sb->s_count) { + list_del_init(&sb->s_list); destroy_super(sb); - ret = 1; - } - return ret; -} - -/* - * Drop a superblock's refcount. - * Returns non-zero if the superblock is about to be destroyed and - * at least is already removed from super_blocks list, so if we are - * making a loop through super blocks then we need to restart. - * The caller must hold sb_lock. - */ -int __put_super_and_need_restart(struct super_block *sb) -{ - /* check for race with generic_shutdown_super() */ - if (list_empty(&sb->s_list)) { - /* super block is removed, need to restart... */ - __put_super(sb); - return 1; } - /* can't be the last, since s_list is still in use */ - sb->s_count--; - BUG_ON(sb->s_count == 0); - return 0; } /** @@ -178,53 +146,48 @@ void put_super(struct super_block *sb) /** - * deactivate_super - drop an active reference to superblock + * deactivate_locked_super - drop an active reference to superblock * @s: superblock to deactivate * - * Drops an active reference to superblock, acquiring a temprory one if - * there is no active references left. In that case we lock superblock, + * Drops an active reference to superblock, converting it into a temprory + * one if there is no other active references left. In that case we * tell fs driver to shut it down and drop the temporary reference we * had just acquired. + * + * Caller holds exclusive lock on superblock; that lock is released. */ -void deactivate_super(struct super_block *s) +void deactivate_locked_super(struct super_block *s) { struct file_system_type *fs = s->s_type; if (atomic_dec_and_test(&s->s_active)) { vfs_dq_off(s, 0); - down_write(&s->s_umount); fs->kill_sb(s); put_filesystem(fs); put_super(s); + } else { + up_write(&s->s_umount); } } -EXPORT_SYMBOL(deactivate_super); +EXPORT_SYMBOL(deactivate_locked_super); /** - * deactivate_locked_super - drop an active reference to superblock + * deactivate_super - drop an active reference to superblock * @s: superblock to deactivate * - * Equivalent of up_write(&s->s_umount); deactivate_super(s);, except that - * it does not unlock it until it's all over. As the result, it's safe to - * use to dispose of new superblock on ->get_sb() failure exits - nobody - * will see the sucker until it's all over. Equivalent using up_write + - * deactivate_super is safe for that purpose only if superblock is either - * safe to use or has NULL ->s_root when we unlock. + * Variant of deactivate_locked_super(), except that superblock is *not* + * locked by caller. If we are going to drop the final active reference, + * lock will be acquired prior to that. */ -void deactivate_locked_super(struct super_block *s) +void deactivate_super(struct super_block *s) { - struct file_system_type *fs = s->s_type; - if (atomic_dec_and_test(&s->s_active)) { - vfs_dq_off(s, 0); - fs->kill_sb(s); - put_filesystem(fs); - put_super(s); - } else { - up_write(&s->s_umount); + if (!atomic_add_unless(&s->s_active, -1, 1)) { + down_write(&s->s_umount); + deactivate_locked_super(s); } } -EXPORT_SYMBOL(deactivate_locked_super); +EXPORT_SYMBOL(deactivate_super); /** * grab_super - acquire an active reference @@ -241,18 +204,15 @@ static int grab_super(struct super_block *s) __releases(sb_lock) { if (atomic_inc_not_zero(&s->s_active)) { spin_unlock(&sb_lock); - down_write(&s->s_umount); return 1; } /* it's going away */ s->s_count++; spin_unlock(&sb_lock); - /* usually that'll be enough for it to die... */ + /* wait for it to die */ down_write(&s->s_umount); up_write(&s->s_umount); put_super(s); - /* ... but in case it wasn't, let's at least yield() */ - yield(); return 0; } @@ -315,8 +275,7 @@ void generic_shutdown_super(struct super_block *sb) } spin_lock(&sb_lock); /* should be initialized for __put_super_and_need_restart() */ - list_del_init(&sb->s_list); - list_del(&sb->s_instances); + list_del_init(&sb->s_instances); spin_unlock(&sb_lock); up_write(&sb->s_umount); } @@ -351,6 +310,7 @@ retry: up_write(&s->s_umount); destroy_super(s); } + down_write(&old->s_umount); return old; } } @@ -402,11 +362,12 @@ EXPORT_SYMBOL(drop_super); */ void sync_supers(void) { - struct super_block *sb; + struct super_block *sb, *n; spin_lock(&sb_lock); -restart: - list_for_each_entry(sb, &super_blocks, s_list) { + list_for_each_entry_safe(sb, n, &super_blocks, s_list) { + if (list_empty(&sb->s_instances)) + continue; if (sb->s_op->write_super && sb->s_dirt) { sb->s_count++; spin_unlock(&sb_lock); @@ -417,14 +378,43 @@ restart: up_read(&sb->s_umount); spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto restart; + __put_super(sb); } } spin_unlock(&sb_lock); } /** + * iterate_supers - call function for all active superblocks + * @f: function to call + * @arg: argument to pass to it + * + * Scans the superblock list and calls given function, passing it + * locked superblock and given argument. + */ +void iterate_supers(void (*f)(struct super_block *, void *), void *arg) +{ + struct super_block *sb, *n; + + spin_lock(&sb_lock); + list_for_each_entry_safe(sb, n, &super_blocks, s_list) { + if (list_empty(&sb->s_instances)) + continue; + sb->s_count++; + spin_unlock(&sb_lock); + + down_read(&sb->s_umount); + if (sb->s_root) + f(sb, arg); + up_read(&sb->s_umount); + + spin_lock(&sb_lock); + __put_super(sb); + } + spin_unlock(&sb_lock); +} + +/** * get_super - get the superblock of a device * @bdev: device to get the superblock for * @@ -432,7 +422,7 @@ restart: * mounted on the device given. %NULL is returned if no match is found. */ -struct super_block * get_super(struct block_device *bdev) +struct super_block *get_super(struct block_device *bdev) { struct super_block *sb; @@ -442,17 +432,20 @@ struct super_block * get_super(struct block_device *bdev) spin_lock(&sb_lock); rescan: list_for_each_entry(sb, &super_blocks, s_list) { + if (list_empty(&sb->s_instances)) + continue; if (sb->s_bdev == bdev) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); + /* still alive? */ if (sb->s_root) return sb; up_read(&sb->s_umount); - /* restart only when sb is no longer on the list */ + /* nope, got unmounted */ spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto rescan; + __put_super(sb); + goto rescan; } } spin_unlock(&sb_lock); @@ -467,7 +460,7 @@ EXPORT_SYMBOL(get_super); * * Scans the superblock list and finds the superblock of the file system * mounted on the device given. Returns the superblock with an active - * reference and s_umount held exclusively or %NULL if none was found. + * reference or %NULL if none was found. */ struct super_block *get_active_super(struct block_device *bdev) { @@ -476,68 +469,49 @@ struct super_block *get_active_super(struct block_device *bdev) if (!bdev) return NULL; +restart: spin_lock(&sb_lock); list_for_each_entry(sb, &super_blocks, s_list) { - if (sb->s_bdev != bdev) + if (list_empty(&sb->s_instances)) continue; - - if (grab_super(sb)) /* drops sb_lock */ - return sb; - - spin_lock(&sb_lock); + if (sb->s_bdev == bdev) { + if (grab_super(sb)) /* drops sb_lock */ + return sb; + else + goto restart; + } } spin_unlock(&sb_lock); return NULL; } -struct super_block * user_get_super(dev_t dev) +struct super_block *user_get_super(dev_t dev) { struct super_block *sb; spin_lock(&sb_lock); rescan: list_for_each_entry(sb, &super_blocks, s_list) { + if (list_empty(&sb->s_instances)) + continue; if (sb->s_dev == dev) { sb->s_count++; spin_unlock(&sb_lock); down_read(&sb->s_umount); + /* still alive? */ if (sb->s_root) return sb; up_read(&sb->s_umount); - /* restart only when sb is no longer on the list */ + /* nope, got unmounted */ spin_lock(&sb_lock); - if (__put_super_and_need_restart(sb)) - goto rescan; + __put_super(sb); + goto rescan; } } spin_unlock(&sb_lock); return NULL; } -SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf) -{ - struct super_block *s; - struct ustat tmp; - struct kstatfs sbuf; - int err = -EINVAL; - - s = user_get_super(new_decode_dev(dev)); - if (s == NULL) - goto out; - err = vfs_statfs(s->s_root, &sbuf); - drop_super(s); - if (err) - goto out; - - memset(&tmp,0,sizeof(struct ustat)); - tmp.f_tfree = sbuf.f_bfree; - tmp.f_tinode = sbuf.f_ffree; - - err = copy_to_user(ubuf,&tmp,sizeof(struct ustat)) ? -EFAULT : 0; -out: - return err; -} - /** * do_remount_sb - asks filesystem to change mount options. * @sb: superblock in question @@ -603,10 +577,12 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force) static void do_emergency_remount(struct work_struct *work) { - struct super_block *sb; + struct super_block *sb, *n; spin_lock(&sb_lock); - list_for_each_entry(sb, &super_blocks, s_list) { + list_for_each_entry_safe(sb, n, &super_blocks, s_list) { + if (list_empty(&sb->s_instances)) + continue; sb->s_count++; spin_unlock(&sb_lock); down_write(&sb->s_umount); @@ -617,8 +593,8 @@ static void do_emergency_remount(struct work_struct *work) do_remount_sb(sb, MS_RDONLY, NULL, 1); } up_write(&sb->s_umount); - put_super(sb); spin_lock(&sb_lock); + __put_super(sb); } spin_unlock(&sb_lock); kfree(work); @@ -969,6 +945,96 @@ out: EXPORT_SYMBOL_GPL(vfs_kern_mount); +/** + * freeze_super -- lock the filesystem and force it into a consistent state + * @super: the super to lock + * + * Syncs the super to make sure the filesystem is consistent and calls the fs's + * freeze_fs. Subsequent calls to this without first thawing the fs will return + * -EBUSY. + */ +int freeze_super(struct super_block *sb) +{ + int ret; + + atomic_inc(&sb->s_active); + down_write(&sb->s_umount); + if (sb->s_frozen) { + deactivate_locked_super(sb); + return -EBUSY; + } + + if (sb->s_flags & MS_RDONLY) { + sb->s_frozen = SB_FREEZE_TRANS; + smp_wmb(); + up_write(&sb->s_umount); + return 0; + } + + sb->s_frozen = SB_FREEZE_WRITE; + smp_wmb(); + + sync_filesystem(sb); + + sb->s_frozen = SB_FREEZE_TRANS; + smp_wmb(); + + sync_blockdev(sb->s_bdev); + if (sb->s_op->freeze_fs) { + ret = sb->s_op->freeze_fs(sb); + if (ret) { + printk(KERN_ERR + "VFS:Filesystem freeze failed\n"); + sb->s_frozen = SB_UNFROZEN; + deactivate_locked_super(sb); + return ret; + } + } + up_write(&sb->s_umount); + return 0; +} +EXPORT_SYMBOL(freeze_super); + +/** + * thaw_super -- unlock filesystem + * @sb: the super to thaw + * + * Unlocks the filesystem and marks it writeable again after freeze_super(). + */ +int thaw_super(struct super_block *sb) +{ + int error; + + down_write(&sb->s_umount); + if (sb->s_frozen == SB_UNFROZEN) { + up_write(&sb->s_umount); + return -EINVAL; + } + + if (sb->s_flags & MS_RDONLY) + goto out; + + if (sb->s_op->unfreeze_fs) { + error = sb->s_op->unfreeze_fs(sb); + if (error) { + printk(KERN_ERR + "VFS:Filesystem thaw failed\n"); + sb->s_frozen = SB_FREEZE_TRANS; + up_write(&sb->s_umount); + return error; + } + } + +out: + sb->s_frozen = SB_UNFROZEN; + smp_wmb(); + wake_up(&sb->s_wait_unfrozen); + deactivate_locked_super(sb); + + return 0; +} +EXPORT_SYMBOL(thaw_super); + static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) { int err;