FAILED: patch "[PATCH] btrfs: zoned: fix critical section of relocation inode" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 19ab78ca86981e0e1e73036fb73a508731a7c078 Mon Sep 17 00:00:00 2001
From: Naohiro Aota <[email protected]>
Date: Tue, 7 Jun 2022 16:08:30 +0900
Subject: [PATCH] btrfs: zoned: fix critical section of relocation inode
writeback

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.

index 588c7c606a2c..9c250b8cd548 100644
@@ -5240,13 +5240,14 @@ int extent_writepages(struct address_space *mapping,
 	 */
 	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;
 	}
 	flush_write_bio(&epd);
+	btrfs_zoned_data_reloc_unlock(BTRFS_I(inode));
 	return ret;
 }