This is a note to let you know that I've just added the patch titled
btrfs: don't wait for writeback on clean pages in extent_write_cache_pages
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-don-t-wait-for-writeback-on-clean-pages-in-extent_write_cache_pages.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5c25699871112853f231e52d51c576d5c759a020 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Mon, 24 Jul 2023 06:26:54 -0700
Subject: btrfs: don't wait for writeback on clean pages in extent_write_cache_pages
From: Christoph Hellwig <hch@xxxxxx>
commit 5c25699871112853f231e52d51c576d5c759a020 upstream.
__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.
CC: stable@xxxxxxxxxxxxxxx # 4.14+
Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/btrfs/extent_io.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4091,6 +4091,12 @@ retry:
continue;
}
+ if (!folio_test_dirty(folio)) {
+ /* Someone wrote it for us. */
+ folio_unlock(folio);
+ continue;
+ }
+
if (wbc->sync_mode != WB_SYNC_NONE) {
if (PageWriteback(page)) {
ret = flush_write_bio(epd);
Patches currently in stable-queue which might be from hch@xxxxxx are
queue-4.19/btrfs-don-t-stop-integrity-writeback-too-early.patch
queue-4.19/btrfs-don-t-wait-for-writeback-on-clean-pages-in-extent_write_cache_pages.patch
