FAILED: patch "[PATCH] btrfs: don't wait for writeback on clean pages in" failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-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]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.14.y
git checkout FETCH_HEAD
git cherry-pick -x 5c25699871112853f231e52d51c576d5c759a020
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023081248-stuffed-rematch-3c0b@gregkh' --subject-prefix 'PATCH 4.14.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 5c25699871112853f231e52d51c576d5c759a020 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <[email protected]>
Date: Mon, 24 Jul 2023 06:26:54 -0700
Subject: [PATCH] btrfs: don't wait for writeback on clean pages in
extent_write_cache_pages

__extent_writepage could have started on more pages than the one it was called for. This happens regularly for zoned file systems, and in theory could happen for compressed I/O if the worker thread was executed very quickly. For such pages extent_write_cache_pages waits for writeback to complete before moving on to the next page, which is highly inefficient as it blocks the flusher thread.

Port over the PageDirty check that was added to write_cache_pages in commit 515f4a037fb ("mm: write_cache_pages optimise page cleaning") to fix this.

index c36eb4956f81..ca765d62324f 100644
@@ -2145,6 +2145,12 @@ static int extent_write_cache_pages(struct address_space *mapping,
 				continue;
 			}
 
+			if (!folio_test_dirty(folio)) {
+				/* Someone wrote it for us. */
+				folio_unlock(folio);
+				continue;
+			}
+
 			if (wbc->sync_mode != WB_SYNC_NONE) {
 				if (folio_test_writeback(folio))
 					submit_write_bio(bio_ctrl, 0);