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[v3,1/3] btrfs: mark resumed async balance as writing

Message ID 72503baa4f47792e9f7b6c3b5dc858e02e778fbf.1648448228.git.naohiro.aota@wdc.com (mailing list archive)
State New, archived
Headers show
Series protect relocation with sb_start_write | expand

Commit Message

Naohiro Aota March 28, 2022, 6:29 a.m. UTC
When btrfs balance is interrupted with umount, the background balance
resumes on the next mount. There is a potential deadlock with FS freezing
here like as described in commit 26559780b953 ("btrfs: zoned: mark
relocation as writing"). Mark the process as sb_writing to avoid it.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Cc: stable@vger.kernel.org # 4.9+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/volumes.c | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 3fd17e87815a..3471698fd831 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4430,10 +4430,12 @@  static int balance_kthread(void *data)
 	struct btrfs_fs_info *fs_info = data;
 	int ret = 0;
 
+	sb_start_write(fs_info->sb);
 	mutex_lock(&fs_info->balance_mutex);
 	if (fs_info->balance_ctl)
 		ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL);
 	mutex_unlock(&fs_info->balance_mutex);
+	sb_end_write(fs_info->sb);
 
 	return ret;
 }