Re: [PATCH 3/3] fs: fix corner case race on freeze_bdev() when sb disappears
From: Jan Kara <jack@suse.cz>
Date: 2018-05-03 15:02:20
Also in:
linux-fsdevel, linux-pm, lkml
On Fri 20-04-18 16:59:04, Luis R. Rodriguez wrote:
freeze_bdev() will bail but leave the bd_fsfreeze_count incremented
if the get_active_super() does not find the superblock on our
super_blocks list to match.
This issue has been present since v2.6.29 during the introduction of the
ioctl_fsfreeze() and ioctl_fsthaw() via commit fcccf502540e3 ("filesystem
freeze: implement generic freeze feature").
I am not aware of any existing races which have triggered this
situation, however, if it does trigger it could mean leaving a
superblock with bd_fsfreeze_count always positive.
Fixes: fcccf502540e3 ("filesystem freeze: implement generic freeze feature")
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>Looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza
quoted hunk ↗ jump to hunk
--- fs/block_dev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/fs/block_dev.c b/fs/block_dev.c index b54966679833..7a532aa58c07 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c@@ -507,8 +507,10 @@ struct super_block *freeze_bdev(struct block_device *bdev) } sb = get_active_super(bdev); - if (!sb) + if (!sb) { + bdev->bd_fsfreeze_count--; goto out; + } if (sb->s_op->freeze_super) error = sb->s_op->freeze_super(sb); else-- 2.16.3
-- Jan Kara [off-list ref] SUSE Labs, CR