+ mm-zswap-cleanup-zswap_reclaim_entry-fix.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm-zswap-cleanup-zswap_reclaim_entry-fix
has been added to the -mm mm-unstable branch.  Its filename is
     mm-zswap-cleanup-zswap_reclaim_entry-fix.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-zswap-cleanup-zswap_reclaim_entry-fix.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Andrew Morton <akpm@linux-foundation.org>
Subject: mm-zswap-cleanup-zswap_reclaim_entry-fix
Date: Thu Dec 14 02:21:39 PM PST 2023

retain comment, per Yosry

Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Chris Li <chriscli@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Vitaly Wool <vitaly.wool@konsulko.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/zswap.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/mm/zswap.c~mm-zswap-cleanup-zswap_reclaim_entry-fix
+++ a/mm/zswap.c
@@ -1457,8 +1457,14 @@ static int zswap_writeback_entry(struct
 	mpol = get_task_policy(current);
 	page = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol,
 				NO_INTERLEAVE_INDEX, &page_was_allocated, true);
-	if (!page)
+	if (!page) {
+		/*
+		 * If we get here because the page is already in swapcache, a
+		 * load may be happening concurrently. It is safe and okay to
+		 * not free the entry. It is also okay to return !0.
+		 */
 		return -ENOMEM;
+	}
 
 	/* Found an existing page, we raced with load/swapin */
 	if (!page_was_allocated) {
_

Patches currently in -mm which might be from akpm@linux-foundation.org are

lib-maple_treec-fix-build-error-due-to-hotfix-alteration.patch
mm-list_lruc-remove-unused-list_lru_from_kmem.patch
mm-memcg-restore-subtree-stats-flushing-fix.patch
mm-zswap-cleanup-zswap_reclaim_entry-fix.patch
mips-fix-r3k_cache_init-build-regression-fix.patch