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filesystem freeze: add error handling of write_super_lockfs/unlockfs
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Currently, ext3 in mainline Linux doesn't have the freeze feature which
suspends write requests.  So, we cannot take a backup which keeps the
filesystem's consistency with the storage device's features (snapshot and
replication) while it is mounted.

In many case, a commercial filesystem (e.g.  VxFS) has the freeze feature
and it would be used to get the consistent backup.

If Linux's standard filesystem ext3 has the freeze feature, we can do it
without a commercial filesystem.

So I have implemented the ioctls of the freeze feature.
I think we can take the consistent backup with the following steps.
1. Freeze the filesystem with the freeze ioctl.
2. Separate the replication volume or create the snapshot
   with the storage device's feature.
3. Unfreeze the filesystem with the unfreeze ioctl.
4. Take the backup from the separated replication volume
   or the snapshot.

This patch:

VFS:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that they can return an error.
Rename write_super_lockfs and unlockfs of the super block operation
freeze_fs and unfreeze_fs to avoid a confusion.

ext3, ext4, xfs, gfs2, jfs:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that write_super_lockfs returns an error if needed,
and unlockfs always returns 0.

reiserfs:
Changed the type of write_super_lockfs and unlockfs from "void"
to "int" so that they always return 0 (success) to keep a current behavior.

Signed-off-by: Takashi Sato <[email protected]>
Signed-off-by: Masayuki Hamaguchi <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Dave Kleikamp <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Alasdair G Kergon <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@torvalds
Takashi Sato authored and torvalds committed Jan 10, 2009
1 parent 69347a2 commit c4be0c1
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Showing 12 changed files with 107 additions and 68 deletions.
8 changes: 4 additions & 4 deletions Documentation/filesystems/Locking
View file
Original file line number Diff line number Diff line change
Expand Up @@ -97,8 +97,8 @@ prototypes:
void (*put_super) (struct super_block *);
void (*write_super) (struct super_block *);
int (*sync_fs)(struct super_block *sb, int wait);
void (*write_super_lockfs) (struct super_block *);
void (*unlockfs) (struct super_block *);
int (*freeze_fs) (struct super_block *);
int (*unfreeze_fs) (struct super_block *);
int (*statfs) (struct dentry *, struct kstatfs *);
int (*remount_fs) (struct super_block *, int *, char *);
void (*clear_inode) (struct inode *);
Expand All @@ -119,8 +119,8 @@ delete_inode: no
put_super: yes yes no
write_super: no yes read
sync_fs: no no read
write_super_lockfs: ?
unlockfs: ?
freeze_fs: ?
unfreeze_fs: ?
statfs: no no no
remount_fs: yes yes maybe (see below)
clear_inode: no
Expand Down
8 changes: 4 additions & 4 deletions Documentation/filesystems/vfs.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -210,8 +210,8 @@ struct super_operations {
void (*put_super) (struct super_block *);
void (*write_super) (struct super_block *);
int (*sync_fs)(struct super_block *sb, int wait);
void (*write_super_lockfs) (struct super_block *);
void (*unlockfs) (struct super_block *);
int (*freeze_fs) (struct super_block *);
int (*unfreeze_fs) (struct super_block *);
int (*statfs) (struct dentry *, struct kstatfs *);
int (*remount_fs) (struct super_block *, int *, char *);
void (*clear_inode) (struct inode *);
Expand Down Expand Up @@ -270,11 +270,11 @@ or bottom half).
a superblock. The second parameter indicates whether the method
should wait until the write out has been completed. Optional.

write_super_lockfs: called when VFS is locking a filesystem and
freeze_fs: called when VFS is locking a filesystem and
forcing it into a consistent state. This method is currently
used by the Logical Volume Manager (LVM).

unlockfs: called when VFS is unlocking a filesystem and making it writable
unfreeze_fs: called when VFS is unlocking a filesystem and making it writable
again.

statfs: called when the VFS needs to get filesystem statistics. This
Expand Down
8 changes: 4 additions & 4 deletions fs/buffer.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -221,8 +221,8 @@ struct super_block *freeze_bdev(struct block_device *bdev)

sync_blockdev(sb->s_bdev);

if (sb->s_op->write_super_lockfs)
sb->s_op->write_super_lockfs(sb);
if (sb->s_op->freeze_fs)
sb->s_op->freeze_fs(sb);
}

sync_blockdev(bdev);
Expand All @@ -242,8 +242,8 @@ void thaw_bdev(struct block_device *bdev, struct super_block *sb)
if (sb) {
BUG_ON(sb->s_bdev != bdev);

if (sb->s_op->unlockfs)
sb->s_op->unlockfs(sb);
if (sb->s_op->unfreeze_fs)
sb->s_op->unfreeze_fs(sb);
sb->s_frozen = SB_UNFROZEN;
smp_wmb();
wake_up(&sb->s_wait_unfrozen);
Expand Down
45 changes: 29 additions & 16 deletions fs/ext3/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -48,8 +48,8 @@ static int ext3_load_journal(struct super_block *, struct ext3_super_block *,
unsigned long journal_devnum);
static int ext3_create_journal(struct super_block *, struct ext3_super_block *,
unsigned int);
static void ext3_commit_super (struct super_block * sb,
struct ext3_super_block * es,
static int ext3_commit_super(struct super_block *sb,
struct ext3_super_block *es,
int sync);
static void ext3_mark_recovery_complete(struct super_block * sb,
struct ext3_super_block * es);
Expand All @@ -60,9 +60,9 @@ static const char *ext3_decode_error(struct super_block * sb, int errno,
char nbuf[16]);
static int ext3_remount (struct super_block * sb, int * flags, char * data);
static int ext3_statfs (struct dentry * dentry, struct kstatfs * buf);
static void ext3_unlockfs(struct super_block *sb);
static int ext3_unfreeze(struct super_block *sb);
static void ext3_write_super (struct super_block * sb);
static void ext3_write_super_lockfs(struct super_block *sb);
static int ext3_freeze(struct super_block *sb);

/*
* Wrappers for journal_start/end.
Expand Down Expand Up @@ -759,8 +759,8 @@ static const struct super_operations ext3_sops = {
.put_super = ext3_put_super,
.write_super = ext3_write_super,
.sync_fs = ext3_sync_fs,
.write_super_lockfs = ext3_write_super_lockfs,
.unlockfs = ext3_unlockfs,
.freeze_fs = ext3_freeze,
.unfreeze_fs = ext3_unfreeze,
.statfs = ext3_statfs,
.remount_fs = ext3_remount,
.clear_inode = ext3_clear_inode,
Expand Down Expand Up @@ -2311,21 +2311,23 @@ static int ext3_create_journal(struct super_block * sb,
return 0;
}

static void ext3_commit_super (struct super_block * sb,
struct ext3_super_block * es,
static int ext3_commit_super(struct super_block *sb,
struct ext3_super_block *es,
int sync)
{
struct buffer_head *sbh = EXT3_SB(sb)->s_sbh;
int error = 0;

if (!sbh)
return;
return error;
es->s_wtime = cpu_to_le32(get_seconds());
es->s_free_blocks_count = cpu_to_le32(ext3_count_free_blocks(sb));
es->s_free_inodes_count = cpu_to_le32(ext3_count_free_inodes(sb));
BUFFER_TRACE(sbh, "marking dirty");
mark_buffer_dirty(sbh);
if (sync)
sync_dirty_buffer(sbh);
error = sync_dirty_buffer(sbh);
return error;
}


Expand Down Expand Up @@ -2439,12 +2441,14 @@ static int ext3_sync_fs(struct super_block *sb, int wait)
* 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 void ext3_write_super_lockfs(struct super_block *sb)
static int ext3_freeze(struct super_block *sb)
{
int error = 0;
journal_t *journal;
sb->s_dirt = 0;

if (!(sb->s_flags & MS_RDONLY)) {
journal_t *journal = EXT3_SB(sb)->s_journal;
journal = EXT3_SB(sb)->s_journal;

/* Now we set up the journal barrier. */
journal_lock_updates(journal);
Expand All @@ -2453,20 +2457,28 @@ static void ext3_write_super_lockfs(struct super_block *sb)
* We don't want to clear needs_recovery flag when we failed
* to flush the journal.
*/
if (journal_flush(journal) < 0)
return;
error = journal_flush(journal);
if (error < 0)
goto out;

/* Journal blocked and flushed, clear needs_recovery flag. */
EXT3_CLEAR_INCOMPAT_FEATURE(sb, EXT3_FEATURE_INCOMPAT_RECOVER);
ext3_commit_super(sb, EXT3_SB(sb)->s_es, 1);
error = ext3_commit_super(sb, EXT3_SB(sb)->s_es, 1);
if (error)
goto out;
}
return 0;

out:
journal_unlock_updates(journal);
return error;
}

/*
* 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 void ext3_unlockfs(struct super_block *sb)
static int ext3_unfreeze(struct super_block *sb)
{
if (!(sb->s_flags & MS_RDONLY)) {
lock_super(sb);
Expand All @@ -2476,6 +2488,7 @@ static void ext3_unlockfs(struct super_block *sb)
unlock_super(sb);
journal_unlock_updates(EXT3_SB(sb)->s_journal);
}
return 0;
}

static int ext3_remount (struct super_block * sb, int * flags, char * data)
Expand Down
45 changes: 31 additions & 14 deletions fs/ext4/super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ struct proc_dir_entry *ext4_proc_root;

static int ext4_load_journal(struct super_block *, struct ext4_super_block *,
unsigned long journal_devnum);
static void ext4_commit_super(struct super_block *sb,
static int ext4_commit_super(struct super_block *sb,
struct ext4_super_block *es, int sync);
static void ext4_mark_recovery_complete(struct super_block *sb,
struct ext4_super_block *es);
Expand All @@ -62,9 +62,9 @@ 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 void ext4_unlockfs(struct super_block *sb);
static int ext4_unfreeze(struct super_block *sb);
static void ext4_write_super(struct super_block *sb);
static void ext4_write_super_lockfs(struct super_block *sb);
static int ext4_freeze(struct super_block *sb);


ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,
Expand Down Expand Up @@ -978,8 +978,8 @@ static const struct super_operations ext4_sops = {
.put_super = ext4_put_super,
.write_super = ext4_write_super,
.sync_fs = ext4_sync_fs,
.write_super_lockfs = ext4_write_super_lockfs,
.unlockfs = ext4_unlockfs,
.freeze_fs = ext4_freeze,
.unfreeze_fs = ext4_unfreeze,
.statfs = ext4_statfs,
.remount_fs = ext4_remount,
.clear_inode = ext4_clear_inode,
Expand Down Expand Up @@ -2888,13 +2888,14 @@ static int ext4_load_journal(struct super_block *sb,
return 0;
}

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

if (!sbh)
return;
return error;
if (buffer_write_io_error(sbh)) {
/*
* Oh, dear. A previous attempt to write the
Expand All @@ -2918,14 +2919,19 @@ static void ext4_commit_super(struct super_block *sb,
BUFFER_TRACE(sbh, "marking dirty");
mark_buffer_dirty(sbh);
if (sync) {
sync_dirty_buffer(sbh);
if (buffer_write_io_error(sbh)) {
error = sync_dirty_buffer(sbh);
if (error)
return error;

error = buffer_write_io_error(sbh);
if (error) {
printk(KERN_ERR "EXT4-fs: I/O error while writing "
"superblock for %s.\n", sb->s_id);
clear_buffer_write_io_error(sbh);
set_buffer_uptodate(sbh);
}
}
return error;
}


Expand Down Expand Up @@ -3058,12 +3064,14 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
* 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 void ext4_write_super_lockfs(struct super_block *sb)
static int ext4_freeze(struct super_block *sb)
{
int error = 0;
journal_t *journal;
sb->s_dirt = 0;

if (!(sb->s_flags & MS_RDONLY)) {
journal_t *journal = EXT4_SB(sb)->s_journal;
journal = EXT4_SB(sb)->s_journal;

if (journal) {
/* Now we set up the journal barrier. */
Expand All @@ -3073,21 +3081,29 @@ static void ext4_write_super_lockfs(struct super_block *sb)
* We don't want to clear needs_recovery flag when we
* failed to flush the journal.
*/
if (jbd2_journal_flush(journal) < 0)
return;
error = jbd2_journal_flush(journal);
if (error < 0)
goto out;
}

/* Journal blocked and flushed, clear needs_recovery flag. */
EXT4_CLEAR_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER);
ext4_commit_super(sb, EXT4_SB(sb)->s_es, 1);
error = ext4_commit_super(sb, EXT4_SB(sb)->s_es, 1);
if (error)
goto out;
}
return 0;
out:
jbd2_journal_unlock_updates(journal);
return error;
}

/*
* 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 void ext4_unlockfs(struct super_block *sb)
static int ext4_unfreeze(struct super_block *sb)
{
if (EXT4_SB(sb)->s_journal && !(sb->s_flags & MS_RDONLY)) {
lock_super(sb);
Expand All @@ -3097,6 +3113,7 @@ static void ext4_unlockfs(struct super_block *sb)
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)
Expand Down
16 changes: 9 additions & 7 deletions fs/gfs2/ops_super.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -211,18 +211,18 @@ static int gfs2_sync_fs(struct super_block *sb, int wait)
}

/**
* gfs2_write_super_lockfs - prevent further writes to the filesystem
* gfs2_freeze - prevent further writes to the filesystem
* @sb: the VFS structure for the filesystem
*
*/

static void gfs2_write_super_lockfs(struct super_block *sb)
static int gfs2_freeze(struct super_block *sb)
{
struct gfs2_sbd *sdp = sb->s_fs_info;
int error;

if (test_bit(SDF_SHUTDOWN, &sdp->sd_flags))
return;
return -EINVAL;

for (;;) {
error = gfs2_freeze_fs(sdp);
Expand All @@ -242,17 +242,19 @@ static void gfs2_write_super_lockfs(struct super_block *sb)
fs_err(sdp, "retrying...\n");
msleep(1000);
}
return 0;
}

/**
* gfs2_unlockfs - reallow writes to the filesystem
* gfs2_unfreeze - reallow writes to the filesystem
* @sb: the VFS structure for the filesystem
*
*/

static void gfs2_unlockfs(struct super_block *sb)
static int gfs2_unfreeze(struct super_block *sb)
{
gfs2_unfreeze_fs(sb->s_fs_info);
return 0;
}

/**
Expand Down Expand Up @@ -688,8 +690,8 @@ const struct super_operations gfs2_super_ops = {
.put_super = gfs2_put_super,
.write_super = gfs2_write_super,
.sync_fs = gfs2_sync_fs,
.write_super_lockfs = gfs2_write_super_lockfs,
.unlockfs = gfs2_unlockfs,
.freeze_fs = gfs2_freeze,
.unfreeze_fs = gfs2_unfreeze,
.statfs = gfs2_statfs,
.remount_fs = gfs2_remount_fs,
.clear_inode = gfs2_clear_inode,
Expand Down
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