[PATCH 6.4 758/800] btrfs: bail out reclaim process if filesystem is read-only

Greg Kroah-Hartman
2023-07-16T20:29:40Z

From: Naohiro Aota <naota@elisp.net>

commit 93463ff7b54626f8276c0bd3d3f968fbf8d5d380 upstream.

When a filesystem is read-only, we cannot reclaim a block group as it
cannot rewrite the data. Just bail out in that case.

Note that it can drop block groups in this case. As we did
sb_start_write(), read-only filesystem means we got a fatal error and
forced read-only. There is no chance to reclaim them again.

Fixes: 18bb8bbf13c1 ("btrfs: zoned: automatically reclaim zones")
CC: stable@vger.kernel.org # 5.15+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/btrfs/block-group.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1798,8 +1798,15 @@ void btrfs_reclaim_bgs_work(struct work_
}
spin_unlock(&bg->lock);

- /* Get out fast, in case we're unmounting the filesystem */
- if (btrfs_fs_closing(fs_info)) {
+ /*
+ * Get out fast, in case we're read-only or unmounting the
+ * filesystem. It is OK to drop block groups from the list even
+ * for the read-only case. As we did sb_start_write(),
+ * "mount -o remount,ro" won't happen and read-only filesystem
+ * means it is forced read-only due to a fatal error. So, it
+ * never gets back to read-write to let us reclaim again.
+ */
+ if (btrfs_need_cleaner_sleep(fs_info)) {
up_write(&space_info->groups_sem);
goto next;
}