On Wed 22-04-09 13:16:16, Trond Myklebust wrote: > On Wed, 2009-04-22 at 17:56 +0200, Jan Kara wrote: > > 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@xxxxxxx> > > --- > > fs/super.c | 25 ++++++++++++++++++++++++- > > fs/sync.c | 3 ++- > > include/linux/fs.h | 2 ++ > > 3 files changed, 28 insertions(+), 2 deletions(-) > > > > diff --git a/fs/super.c b/fs/super.c > > index 786fe7d..4f56333 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 +502,29 @@ 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) { > > + 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); > > What's the point of going to all this trouble of upping the sb->s_count, > and grabbing sb->s_umount if there is no sb->s_bdev to sync in the first > place? Thanks for the comment. Yes, we could save something here. I can improve this and similarly my next patch. I'll just wait till tomorrow whether someone else does not have other comments... > > > + 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 Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html