btrfs: don't hold CPU for too long when defragging a file

There is a user report about "btrfs filesystem defrag" causing 120s
timeout problem.

For btrfs_defrag_file() it will iterate all file extents if called from
defrag ioctl, thus it can take a long time.

There is no reason not to release the CPU during such a long operation.

Add cond_resched() after defragged one cluster.

CC: stable@vger.kernel.org # 5.16
Link: https://lore.kernel.org/linux-btrfs/10e51417-2203-f0a4-2021-86c8511cc367@gmx.com
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 925522756e285d650bdf261ae69221b781897133..b51c8b783f40a3c15763ddad75d90b0bed3db720 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1629,6 +1629,7 @@ int btrfs_defrag_file(struct inode *inode, struct file_ra_state *ra,
                        ret = 0;
                        break;
                }
+               cond_resched();
        }
 
        if (ra_allocated)