[PATCH 0/4] Fix sys_sync() and cleanup code (version 3)

[PATCH 0/4] Fix sys_sync() and cleanup code (version 3)

[Jan Kara]

  Hi,

  this is a next version of the patches. I've modified comments a bit
and mainly fixed a return value of __fsync_super() (forgot to commit
the fix before). Thanks to Trond and Christoph for useful comments.

								Honza

[PATCH 1/4] vfs: Fix sys_sync() and fsync_super() reliability (version 3)

[Jan Kara]

So far, do_sync() called:
  sync_inodes(0);
  sync_supers();
  sync_filesystems(0);
  sync_filesystems(1);
  sync_inodes(1);

This ordering makes it kind of hard for filesystems as sync_inodes(0) need not
submit all the IO (for example it skips inodes with I_SYNC set) so e.g. forcing
transaction to disk in ->sync_fs() is not really enough. Therefore sys_sync has
not been completely reliable on some filesystems (ext3, ext4, reiserfs, ocfs2
and others are hit by this) when racing e.g. with background writeback. A
similar problem hits also other filesystems (e.g. ext2) because of
write_supers() being called before the sync_inodes(1).

Change the ordering of calls in do_sync() - this requires a new function
sync_blkdevs() to preserve the property that block devices are always synced
after write_super() / sync_fs() call.

The same issue is fixed in __fsync_super() function used on umount /
remount read-only.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/super.c         |   27 ++++++++++++++++++++++++++-
 fs/sync.c          |    3 ++-
 include/linux/fs.h |    2 ++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 786fe7d..4826540 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -267,6 +267,7 @@ void __fsync_super(struct super_block *sb)
 {
 	sync_inodes_sb(sb, 0);
 	vfs_dq_sync(sb);
+	sync_inodes_sb(sb, 1);
 	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
 		sb->s_op->write_super(sb);
@@ -274,7 +275,6 @@ void __fsync_super(struct super_block *sb)
 	if (sb->s_op->sync_fs)
 		sb->s_op->sync_fs(sb, 1);
 	sync_blockdev(sb->s_bdev);
-	sync_inodes_sb(sb, 1);
 }
 
 /*
@@ -502,6 +502,31 @@ restart:
 	mutex_unlock(&mutex);
 }
 
+/*
+ *  Sync all block devices underlying some superblock
+ */
+void sync_blockdevs(void)
+{
+	struct super_block *sb;
+
+	spin_lock(&sb_lock);
+restart:
+	list_for_each_entry(sb, &super_blocks, s_list) {
+		if (!sb->s_bdev)
+			continue;
+		sb->s_count++;
+		spin_unlock(&sb_lock);
+		down_read(&sb->s_umount);
+		if (sb->s_root)
+			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);
+}
+
 /**
  *	get_super - get the superblock of a device
  *	@bdev: device to get the superblock for
diff --git a/fs/sync.c b/fs/sync.c
index 7abc65f..fa14e42 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -26,10 +26,11 @@ static void do_sync(unsigned long wait)
 	wakeup_pdflush(0);
 	sync_inodes(0);		/* All mappings, inodes and their blockdevs */
 	vfs_dq_sync(NULL);
+	sync_inodes(wait);	/* Mappings, inodes and blockdevs, again. */
 	sync_supers();		/* Write the superblocks */
 	sync_filesystems(0);	/* Start syncing the filesystems */
 	sync_filesystems(wait);	/* Waitingly sync the filesystems */
-	sync_inodes(wait);	/* Mappings, inodes and blockdevs, again. */
+	sync_blockdevs();
 	if (!wait)
 		printk("Emergency Sync complete\n");
 	if (unlikely(laptop_mode))
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 5bed436..4bad02e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1942,6 +1942,7 @@ extern void bdput(struct block_device *);
 extern struct block_device *open_by_devnum(dev_t, fmode_t);
 extern void invalidate_bdev(struct block_device *);
 extern int sync_blockdev(struct block_device *bdev);
+extern void sync_blockdevs(void);
 extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
 extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
@@ -1951,6 +1952,7 @@ extern int fsync_no_super(struct block_device *);
 #else
 static inline void bd_forget(struct inode *inode) {}
 static inline int sync_blockdev(struct block_device *bdev) { return 0; }
+static inline void sync_blockdevs(void) { }
 static inline void invalidate_bdev(struct block_device *bdev) {}
 
 static inline struct super_block *freeze_bdev(struct block_device *sb)
-- 
1.6.0.2

[PATCH 2/4] vfs: Call ->sync_fs() even if s_dirt is 0 (version 3)

[Jan Kara]

sync_filesystems() has a condition that if wait == 0 and s_dirt == 0, then
->sync_fs() isn't called. This does not really make much sence since s_dirt is
generally used by a filesystem to mean that ->write_super() needs to be called.
But ->sync_fs() does different things. I even suspect that some filesystems
(btrfs?) sets s_dirt just to fool this logic.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/super.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/super.c b/fs/super.c
index 4826540..d9759e0 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -490,7 +490,7 @@ restart:
 		spin_unlock(&sb_lock);
 		down_read(&sb->s_umount);
 		async_synchronize_full_domain(&sb->s_async_list);
-		if (sb->s_root && (wait || sb->s_dirt))
+		if (sb->s_root)
 			sb->s_op->sync_fs(sb, wait);
 		up_read(&sb->s_umount);
 		/* restart only when sb is no longer on the list */
-- 
1.6.0.2

[PATCH 3/4] vfs: Make __fsync_super() a static function (version 3)

[Jan Kara]

__fsync_super() does the same thing as fsync_super(). So change the only
caller to use fsync_super() and make __fsync_super() static. This removes
unnecessarily duplicated call to sync_blockdev() and prepares ground
for the changes to __fsync_super() in the following patches.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/block_dev.c     |    2 +-
 fs/super.c         |    5 ++---
 include/linux/fs.h |    1 -
 3 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index f45dbc1..48d1290 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -240,7 +240,7 @@ struct super_block *freeze_bdev(struct block_device *bdev)
 		sb->s_frozen = SB_FREEZE_WRITE;
 		smp_wmb();
 
-		__fsync_super(sb);
+		fsync_super(sb);
 
 		sb->s_frozen = SB_FREEZE_TRANS;
 		smp_wmb();
diff --git a/fs/super.c b/fs/super.c
index d9759e0..4c92068 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -263,7 +263,7 @@ EXPORT_SYMBOL(unlock_super);
  * device.  Takes the superblock lock.  Requires a second blkdev
  * flush by the caller to complete the operation.
  */
-void __fsync_super(struct super_block *sb)
+static int __fsync_super(struct super_block *sb)
 {
 	sync_inodes_sb(sb, 0);
 	vfs_dq_sync(sb);
@@ -284,8 +284,7 @@ void __fsync_super(struct super_block *sb)
  */
 int fsync_super(struct super_block *sb)
 {
-	__fsync_super(sb);
-	return sync_blockdev(sb->s_bdev);
+	return __fsync_super(sb);
 }
 EXPORT_SYMBOL_GPL(fsync_super);
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4bad02e..47a67c9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2084,7 +2084,6 @@ extern int filemap_fdatawrite_range(struct address_space *mapping,
 extern int vfs_fsync(struct file *file, struct dentry *dentry, int datasync);
 extern void sync_supers(void);
 extern void sync_filesystems(int wait);
-extern void __fsync_super(struct super_block *sb);
 extern void emergency_sync(void);
 extern void emergency_remount(void);
 extern int do_remount_sb(struct super_block *sb, int flags,
-- 
1.6.0.2

Re: [PATCH 3/4] vfs: Make __fsync_super() a static function (version 3)

[Trond Myklebust]

On Thu, 2009-04-23 at 23:35 +0200, Jan Kara wrote:
> __fsync_super() does the same thing as fsync_super(). So change the only
> caller to use fsync_super() and make __fsync_super() static. This removes
> unnecessarily duplicated call to sync_blockdev() and prepares ground
> for the changes to __fsync_super() in the following patches.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/block_dev.c     |    2 +-
>  fs/super.c         |    5 ++---
>  include/linux/fs.h |    1 -
>  3 files changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index f45dbc1..48d1290 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -240,7 +240,7 @@ struct super_block *freeze_bdev(struct block_device *bdev)
>  		sb->s_frozen = SB_FREEZE_WRITE;
>  		smp_wmb();
>  
> -		__fsync_super(sb);
> +		fsync_super(sb);
>  
>  		sb->s_frozen = SB_FREEZE_TRANS;
>  		smp_wmb();
> diff --git a/fs/super.c b/fs/super.c
> index d9759e0..4c92068 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -263,7 +263,7 @@ EXPORT_SYMBOL(unlock_super);
>   * device.  Takes the superblock lock.  Requires a second blkdev
>   * flush by the caller to complete the operation.
>   */
> -void __fsync_super(struct super_block *sb)
> +static int __fsync_super(struct super_block *sb)
>  {
>  	sync_inodes_sb(sb, 0);
>  	vfs_dq_sync(sb);

Still missing the return value here :-)

> @@ -284,8 +284,7 @@ void __fsync_super(struct super_block *sb)
>   */
>  int fsync_super(struct super_block *sb)
>  {
> -	__fsync_super(sb);
> -	return sync_blockdev(sb->s_bdev);
> +	return __fsync_super(sb);
>  }
>  EXPORT_SYMBOL_GPL(fsync_super);
>  
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 4bad02e..47a67c9 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -2084,7 +2084,6 @@ extern int filemap_fdatawrite_range(struct address_space *mapping,
>  extern int vfs_fsync(struct file *file, struct dentry *dentry, int datasync);
>  extern void sync_supers(void);
>  extern void sync_filesystems(int wait);
> -extern void __fsync_super(struct super_block *sb);
>  extern void emergency_sync(void);
>  extern void emergency_remount(void);
>  extern int do_remount_sb(struct super_block *sb, int flags,

Re: [PATCH 3/4] vfs: Make __fsync_super() a static function (version 3)

[Jan Kara]

On Thu 23-04-09 17:39:50, Trond Myklebust wrote:
> On Thu, 2009-04-23 at 23:35 +0200, Jan Kara wrote:
> > __fsync_super() does the same thing as fsync_super(). So change the only
> > caller to use fsync_super() and make __fsync_super() static. This removes
> > unnecessarily duplicated call to sync_blockdev() and prepares ground
> > for the changes to __fsync_super() in the following patches.
> > 
> > Signed-off-by: Jan Kara <jack@suse.cz>
> > ---
> >  fs/block_dev.c     |    2 +-
> >  fs/super.c         |    5 ++---
> >  include/linux/fs.h |    1 -
> >  3 files changed, 3 insertions(+), 5 deletions(-)
> > 
> > diff --git a/fs/block_dev.c b/fs/block_dev.c
> > index f45dbc1..48d1290 100644
> > --- a/fs/block_dev.c
> > +++ b/fs/block_dev.c
> > @@ -240,7 +240,7 @@ struct super_block *freeze_bdev(struct block_device *bdev)
> >  		sb->s_frozen = SB_FREEZE_WRITE;
> >  		smp_wmb();
> >  
> > -		__fsync_super(sb);
> > +		fsync_super(sb);
> >  
> >  		sb->s_frozen = SB_FREEZE_TRANS;
> >  		smp_wmb();
> > diff --git a/fs/super.c b/fs/super.c
> > index d9759e0..4c92068 100644
> > --- a/fs/super.c
> > +++ b/fs/super.c
> > @@ -263,7 +263,7 @@ EXPORT_SYMBOL(unlock_super);
> >   * device.  Takes the superblock lock.  Requires a second blkdev
> >   * flush by the caller to complete the operation.
> >   */
> > -void __fsync_super(struct super_block *sb)
> > +static int __fsync_super(struct super_block *sb)
> >  {
> >  	sync_inodes_sb(sb, 0);
> >  	vfs_dq_sync(sb);
> 
> Still missing the return value here :-)
  Ah, OK, but it's fixed in the last patch. I'll fix it in this one as well
for next time. Thanks.

									Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR

[PATCH 4/4] vfs: Make sys_sync() use fsync_super() (version 3)

[Jan Kara]

It is unnecessarily fragile to have two places (fsync_super() and do_sync())
doing data integrity sync of the filesystem. Alter __fsync_super() to
accommodate needs of both callers and use it. So after this patch
__fsync_super() is the only place where we gather all the calls needed to
properly send all data on a filesystem to disk.

Nice bonus is that we get a complete livelock avoidance and write_supers()
is now only used for periodic writeback of superblocks.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/block_dev.c            |   15 ++++++---
 fs/fs-writeback.c         |   49 -------------------------------
 fs/super.c                |   70 +++++++++++++++------------------------------
 fs/sync.c                 |   31 ++++++-------------
 include/linux/fs.h        |    4 +-
 include/linux/writeback.h |    1 -
 6 files changed, 45 insertions(+), 125 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 48d1290..2609cce 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -175,17 +175,22 @@ blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 				iov, offset, nr_segs, blkdev_get_blocks, NULL);
 }
 
+int __sync_blockdev(struct block_device *bdev, int wait)
+{
+	if (!bdev)
+		return 0;
+	if (!wait)
+		return filemap_flush(bdev->bd_inode->i_mapping);
+	return filemap_write_and_wait(bdev->bd_inode->i_mapping);
+}
+
 /*
  * Write out and wait upon all the dirty data associated with a block
  * device via its mapping.  Does not take the superblock lock.
  */
 int sync_blockdev(struct block_device *bdev)
 {
-	int ret = 0;
-
-	if (bdev)
-		ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
-	return ret;
+	return __sync_blockdev(bdev, 1);
 }
 EXPORT_SYMBOL(sync_blockdev);
 
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 91013ff..e0fb2e7 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -679,55 +679,6 @@ void sync_inodes_sb(struct super_block *sb, int wait)
 }
 
 /**
- * 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) {
-		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);
-}
-
-void sync_inodes(int wait)
-{
-	__sync_inodes(0);
-
-	if (wait)
-		__sync_inodes(1);
-}
-
-/**
  * write_inode_now	-	write an inode to disk
  * @inode: inode to write to disk
  * @sync: whether the write should be synchronous or not
diff --git a/fs/super.c b/fs/super.c
index 4c92068..b5d7dfb 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -258,23 +258,23 @@ EXPORT_SYMBOL(lock_super);
 EXPORT_SYMBOL(unlock_super);
 
 /*
- * Write out and wait upon all dirty data associated with this
- * superblock.  Filesystem data as well as the underlying block
- * device.  Takes the superblock lock.  Requires a second blkdev
- * flush by the caller to complete the operation.
+ * Do the filesystem syncing work. For simple filesystems sync_inodes_sb(sb, 0)
+ * just dirties buffers with inodes so we have to submit IO for these buffers
+ * via __sync_blockdev(). This also speeds up the wait == 1 case since in that
+ * case write_inode() functions do sync_dirty_buffer() and thus effectively
+ * write one block at a time.
  */
-static int __fsync_super(struct super_block *sb)
+static int __fsync_super(struct super_block *sb, int wait)
 {
-	sync_inodes_sb(sb, 0);
 	vfs_dq_sync(sb);
-	sync_inodes_sb(sb, 1);
+	sync_inodes_sb(sb, wait);
 	lock_super(sb);
 	if (sb->s_dirt && sb->s_op->write_super)
 		sb->s_op->write_super(sb);
 	unlock_super(sb);
 	if (sb->s_op->sync_fs)
-		sb->s_op->sync_fs(sb, 1);
-	sync_blockdev(sb->s_bdev);
+		sb->s_op->sync_fs(sb, wait);
+	return __sync_blockdev(sb->s_bdev, wait);
 }
 
 /*
@@ -284,7 +284,12 @@ static int __fsync_super(struct super_block *sb)
  */
 int fsync_super(struct super_block *sb)
 {
-	return __fsync_super(sb);
+	int ret;
+
+	ret = __fsync_super(sb, 0);
+	if (ret < 0)
+		return ret;
+	return __fsync_super(sb, 1);
 }
 EXPORT_SYMBOL_GPL(fsync_super);
 
@@ -448,20 +453,18 @@ restart:
 }
 
 /*
- * Call the ->sync_fs super_op against all filesystems which are r/w and
- * which implement it.
+ * Sync all the data for all the filesystems (called by sys_sync() and
+ * emergency sync)
  *
  * This operation is careful to avoid the livelock which could easily happen
- * if two or more filesystems are being continuously dirtied.  s_need_sync_fs
+ * if two or more filesystems are being continuously dirtied.  s_need_sync
  * is used only here.  We set it against all filesystems and then clear it as
  * we sync them.  So redirtied filesystems are skipped.
  *
  * But if process A is currently running sync_filesystems and then process B
- * calls sync_filesystems as well, process B will set all the s_need_sync_fs
+ * calls sync_filesystems as well, process B will set all the s_need_sync
  * flags again, which will cause process A to resync everything.  Fix that with
  * a local mutex.
- *
- * (Fabian) Avoid sync_fs with clean fs & wait mode 0
  */
 void sync_filesystems(int wait)
 {
@@ -471,18 +474,16 @@ void sync_filesystems(int wait)
 	mutex_lock(&mutex);		/* Could be down_interruptible */
 	spin_lock(&sb_lock);
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (!sb->s_op->sync_fs)
-			continue;
 		if (sb->s_flags & MS_RDONLY)
 			continue;
-		sb->s_need_sync_fs = 1;
+		sb->s_need_sync = 1;
 	}
 
 restart:
 	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (!sb->s_need_sync_fs)
+		if (!sb->s_need_sync)
 			continue;
-		sb->s_need_sync_fs = 0;
+		sb->s_need_sync = 0;
 		if (sb->s_flags & MS_RDONLY)
 			continue;	/* hm.  Was remounted r/o meanwhile */
 		sb->s_count++;
@@ -490,7 +491,7 @@ restart:
 		down_read(&sb->s_umount);
 		async_synchronize_full_domain(&sb->s_async_list);
 		if (sb->s_root)
-			sb->s_op->sync_fs(sb, wait);
+			__fsync_super(sb, wait);
 		up_read(&sb->s_umount);
 		/* restart only when sb is no longer on the list */
 		spin_lock(&sb_lock);
@@ -501,31 +502,6 @@ restart:
 	mutex_unlock(&mutex);
 }
 
-/*
- *  Sync all block devices underlying some superblock
- */
-void sync_blockdevs(void)
-{
-	struct super_block *sb;
-
-	spin_lock(&sb_lock);
-restart:
-	list_for_each_entry(sb, &super_blocks, s_list) {
-		if (!sb->s_bdev)
-			continue;
-		sb->s_count++;
-		spin_unlock(&sb_lock);
-		down_read(&sb->s_umount);
-		if (sb->s_root)
-			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);
-}
-
 /**
  *	get_super - get the superblock of a device
  *	@bdev: device to get the superblock for
diff --git a/fs/sync.c b/fs/sync.c
index fa14e42..86c6a86 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -17,35 +17,24 @@
 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
 			SYNC_FILE_RANGE_WAIT_AFTER)
 
-/*
- * sync everything.  Start out by waking pdflush, because that writes back
- * all queues in parallel.
- */
-static void do_sync(unsigned long wait)
+SYSCALL_DEFINE0(sync)
 {
-	wakeup_pdflush(0);
-	sync_inodes(0);		/* All mappings, inodes and their blockdevs */
-	vfs_dq_sync(NULL);
-	sync_inodes(wait);	/* Mappings, inodes and blockdevs, again. */
-	sync_supers();		/* Write the superblocks */
-	sync_filesystems(0);	/* Start syncing the filesystems */
-	sync_filesystems(wait);	/* Waitingly sync the filesystems */
-	sync_blockdevs();
-	if (!wait)
-		printk("Emergency Sync complete\n");
+	sync_filesystems(0);
+	sync_filesystems(1);
 	if (unlikely(laptop_mode))
 		laptop_sync_completion();
-}
-
-SYSCALL_DEFINE0(sync)
-{
-	do_sync(1);
 	return 0;
 }
 
 static void do_sync_work(struct work_struct *work)
 {
-	do_sync(0);
+	/*
+	 * Sync twice to reduce the possibility we skipped some inodes / pages
+	 * because they were temporarily locked
+	 */
+	sync_filesystems(0);
+	sync_filesystems(0);
+	printk("Emergency Sync complete\n");
 	kfree(work);
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 47a67c9..be2be8d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1321,7 +1321,7 @@ struct super_block {
 	struct rw_semaphore	s_umount;
 	struct mutex		s_lock;
 	int			s_count;
-	int			s_need_sync_fs;
+	int			s_need_sync;
 	atomic_t		s_active;
 #ifdef CONFIG_SECURITY
 	void                    *s_security;
@@ -1942,7 +1942,7 @@ extern void bdput(struct block_device *);
 extern struct block_device *open_by_devnum(dev_t, fmode_t);
 extern void invalidate_bdev(struct block_device *);
 extern int sync_blockdev(struct block_device *bdev);
-extern void sync_blockdevs(void);
+extern int __sync_blockdev(struct block_device *bdev, int wait);
 extern struct super_block *freeze_bdev(struct block_device *);
 extern void emergency_thaw_all(void);
 extern int thaw_bdev(struct block_device *bdev, struct super_block *sb);
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 9c1ed1f..943d1c9 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -79,7 +79,6 @@ struct writeback_control {
 void writeback_inodes(struct writeback_control *wbc);
 int inode_wait(void *);
 void sync_inodes_sb(struct super_block *, int wait);
-void sync_inodes(int wait);
 
 /* writeback.h requires fs.h; it, too, is not included from here. */
 static inline void wait_on_inode(struct inode *inode)
-- 
1.6.0.2

Re: [PATCH 0/4] Fix sys_sync() and cleanup code (version 3)

[Christoph Hellwig]

On Thu, Apr 23, 2009 at 11:35:32PM +0200, Jan Kara wrote:
>   Hi,
> 
>   this is a next version of the patches. I've modified comments a bit
> and mainly fixed a return value of __fsync_super() (forgot to commit
> the fix before). Thanks to Trond and Christoph for useful comments.

FYI this (or rather the previous one) seems to do fine running xfsqa.

Re: [PATCH 0/4] Fix sys_sync() and cleanup code (version 3)

[Christoph Hellwig]

Any chance you could move sync_filesystems to fs/sync.c?  It fits in
there much better.  Same is probably true for (__)fsync_super, which
could also use a better name..

Re: [PATCH 0/4] Fix sys_sync() and cleanup code (version 3)

[Jan Kara]

On Sun 26-04-09 07:54:10, Christoph Hellwig wrote:
> Any chance you could move sync_filesystems to fs/sync.c?  It fits in
> there much better.  Same is probably true for (__)fsync_super, which
> could also use a better name..
  OK, I've moved the syncing code to sync.c and renamed fsync_super() to
sync_filesystem() which better describes what it does I think.

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR