[merged mm-hotfixes-stable] mm-mglru-only-clear-kswapd_failures-if-reclaimable.patch removed from -mm tree

[merged mm-hotfixes-stable] mm-mglru-only-clear-kswapd_failures-if-reclaimable.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/mglru: only clear kswapd_failures if reclaimable
has been removed from the -mm tree.  Its filename was
     mm-mglru-only-clear-kswapd_failures-if-reclaimable.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Wei Xu <weixugc@google.com>
Subject: mm/mglru: only clear kswapd_failures if reclaimable
Date: Mon, 14 Oct 2024 22:12:11 +0000

lru_gen_shrink_node() unconditionally clears kswapd_failures, which can
prevent kswapd from sleeping and cause 100% kswapd cpu usage even when
kswapd repeatedly fails to make progress in reclaim.

Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes some
progress, similar to shrink_node().

I happened to run into this problem in one of my tests recently.  It
requires a combination of several conditions: The allocator needs to
allocate a right amount of pages such that it can wake up kswapd
without itself being OOM killed; there is no memory for kswapd to
reclaim (My test disables swap and cleans page cache first); no other
process frees enough memory at the same time.

Link: https://lkml.kernel.org/r/20241014221211.832591-1-weixugc@google.com
Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: Wei Xu <weixugc@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Jan Alexander Steffens <heftig@archlinux.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/vmscan.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/vmscan.c~mm-mglru-only-clear-kswapd_failures-if-reclaimable
+++ a/mm/vmscan.c
@@ -4963,8 +4963,8 @@ static void lru_gen_shrink_node(struct p
 
 	blk_finish_plug(&plug);
 done:
-	/* kswapd should never fail */
-	pgdat->kswapd_failures = 0;
+	if (sc->nr_reclaimed > reclaimed)
+		pgdat->kswapd_failures = 0;
 }
 
 /******************************************************************************
_

Patches currently in -mm which might be from weixugc@google.com are