[PATCH 5.15 18/30] btrfs: zoned: fix critical section of relocation inode writeback

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Naohiro Aota <naohiro.aota@wdc.com>

commit 19ab78ca86981e0e1e73036fb73a508731a7c078 upstream.

We use btrfs_zoned_data_reloc_{lock,unlock} to allow only one process to
write out to the relocation inode. That critical section must include all
the IO submission for the inode. However, flush_write_bio() in
extent_writepages() is out of the critical section, causing an IO
submission outside of the lock. This leads to an out of the order IO
submission and fail the relocation process.

Fix it by extending the critical section.

Fixes: 35156d852762 ("btrfs: zoned: only allow one process to add pages to a relocation inode")
CC: stable@vger.kernel.org # 5.16+
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/extent_io.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5152,13 +5152,14 @@ int extent_writepages(struct address_spa
 	 */
 	btrfs_zoned_data_reloc_lock(BTRFS_I(inode));
 	ret = extent_write_cache_pages(mapping, wbc, &epd);
-	btrfs_zoned_data_reloc_unlock(BTRFS_I(inode));
 	ASSERT(ret <= 0);
 	if (ret < 0) {
+		btrfs_zoned_data_reloc_unlock(BTRFS_I(inode));
 		end_write_bio(&epd, ret);
 		return ret;
 	}
 	ret = flush_write_bio(&epd);
+	btrfs_zoned_data_reloc_unlock(BTRFS_I(inode));
 	return ret;
 }