btrfs: bail out reclaim process if filesystem is read-only

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>

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 6165075..9d9f09f 100644 (file)
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1794,8 +1794,15 @@ void btrfs_reclaim_bgs_work(struct 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;
                }