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authorFilipe Manana <fdmanana@suse.com>2020-06-15 20:46:01 +0300
committerDavid Sterba <dsterba@suse.com>2020-06-16 20:22:27 +0300
commitf2cb2f39ccc30fa13d3ac078d461031a63960e5b (patch)
tree10e3e1bb30ead913de9ca2b878d0a775059110a1 /fs
parente7a79811d0db136dc2d336b56d54cf1b774ce972 (diff)
downloadlinux-f2cb2f39ccc30fa13d3ac078d461031a63960e5b.tar.xz
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.c2
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);