diff options
| author |   Filipe Manana <fdmanana@suse.com> | 2020-06-15 18:46:01 +0100 |
|---|---|---|
| committer |   David Sterba <dsterba@suse.com> | 2020-06-16 19:22:27 +0200 |
| commit | f2cb2f39ccc30fa13d3ac078d461031a63960e5b (patch) | |
| tree | 10e3e1bb30ead913de9ca2b878d0a775059110a1 /fs | |
| parent | btrfs: check if a log root exists before locking the log_mutex on unlink (diff) | |
| download | wireguard-linux-f2cb2f39ccc30fa13d3ac078d461031a63960e5b.tar.xz wireguard-linux-f2cb2f39ccc30fa13d3ac078d461031a63960e5b.zip | |
btrfs: fix hang on snapshot creation after RWF_NOWAIT write
If we do a successful RWF_NOWAIT write we end up locking the snapshot lock
of the inode, through a call to check_can_nocow(), but we never unlock it.
This means the next attempt to create a snapshot on the subvolume will
hang forever.
Trivial reproducer:
$ mkfs.btrfs -f /dev/sdb
$ mount /dev/sdb /mnt
$ touch /mnt/foobar
$ chattr +C /mnt/foobar
$ xfs_io -d -c "pwrite -S 0xab 0 64K" /mnt/foobar
$ xfs_io -d -c "pwrite -N -V 1 -S 0xfe 0 64K" /mnt/foobar
$ btrfs subvolume snapshot -r /mnt /mnt/snap
--> hangs
Fix this by unlocking the snapshot lock if check_can_nocow() returned
success.
Fixes: edf064e7c6fec3 ("btrfs: nowait aio support")
CC: stable@vger.kernel.org # 4.14+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/btrfs/file.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 2c14312b05e8..04faa04fccd1 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1914,6 +1914,8 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb, inode_unlock(inode); return -EAGAIN; } + /* check_can_nocow() locks the snapshot lock on success */ + btrfs_drew_write_unlock(&root->snapshot_lock); } current->backing_dev_info = inode_to_bdi(inode); |