linux-kernel - [PATCH 5.16 028/227] btrfs: dont hold CPU for too long when defragging a file

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Message-Id: <20220221084935.777644127@linuxfoundation.org>
Date:   Mon, 21 Feb 2022 09:47:27 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Qu Wenruo <wqu@...e.com>,
        David Sterba <dsterba@...e.com>
Subject: [PATCH 5.16 028/227] btrfs: dont hold CPU for too long when defragging a file

From: Qu Wenruo <wqu@...e.com>

commit ea0eba69a2a8125229b1b6011644598039bc53aa upstream.

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@...r.kernel.org # 5.16
Link: https://lore.kernel.org/linux-btrfs/10e51417-2203-f0a4-2021-86c8511cc367@gmx.com
Signed-off-by: Qu Wenruo <wqu@...e.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/btrfs/ioctl.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1603,6 +1603,7 @@ int btrfs_defrag_file(struct inode *inod
 			ret = 0;
 			break;
 		}
+		cond_resched();
 	}
 
 	if (ra_allocated)