+ mm-page_alloc-dont-wake-kswapd-from-rmqueue-unless-__gfp_kswapd_reclaim-is-specified.patch added to mm-unstable branch

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

The patch titled
     Subject: mm/page_alloc: don't wake kswapd from rmqueue() unless __GFP_KSWAPD_RECLAIM is specified
has been added to the -mm mm-unstable branch.  Its filename is
     mm-page_alloc-dont-wake-kswapd-from-rmqueue-unless-__gfp_kswapd_reclaim-is-specified.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-dont-wake-kswapd-from-rmqueue-unless-__gfp_kswapd_reclaim-is-specified.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: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Subject: mm/page_alloc: don't wake kswapd from rmqueue() unless __GFP_KSWAPD_RECLAIM is specified
Date: Sun, 14 May 2023 09:28:56 +0900

Commit 73444bc4d8f9 ("mm, page_alloc: do not wake kswapd with zone lock
held") moved wakeup_kswapd() from steal_suitable_fallback() to rmqueue()
using ZONE_BOOSTED_WATERMARK flag.

Only allocation contexts that include ALLOC_KSWAPD (which corresponds to
__GFP_KSWAPD_RECLAIM) should wake kswapd, for callers are supposed to
remove __GFP_KSWAPD_RECLAIM if trying to hold pgdat->kswapd_wait has a
risk of deadlock.  But since zone->flags is a shared variable, a thread
doing !__GFP_KSWAPD_RECLAIM allocation request might observe this flag
being set immediately after another thread doing __GFP_KSWAPD_RECLAIM
allocation request set this flag, causing possibility of deadlock.

Link: https://lkml.kernel.org/r/c3c3dacf-dd3b-77c9-f96a-d0982b4b2a4f@I-love.SAKURA.ne.jp
Fixes: 73444bc4d8f9 ("mm, page_alloc: do not wake kswapd with zone lock held")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page_alloc.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_alloc-dont-wake-kswapd-from-rmqueue-unless-__gfp_kswapd_reclaim-is-specified
+++ a/mm/page_alloc.c
@@ -2863,7 +2863,8 @@ struct page *rmqueue(struct zone *prefer
 
 out:
 	/* Separate test+clear to avoid unnecessary atomics */
-	if (unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
+	if ((alloc_flags & ALLOC_KSWAPD) &&
+	    unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
 		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
 		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
 	}
_

Patches currently in -mm which might be from penguin-kernel@I-love.SAKURA.ne.jp are

workingset-refactor-lru-refault-to-expose-refault-recency-check-fix.patch
kasankmsan-remove-__gfp_kswapd_reclaim-usage-from-kasan-kmsan.patch
mm-page_alloc-dont-wake-kswapd-from-rmqueue-unless-__gfp_kswapd_reclaim-is-specified.patch
debugobjects-turn-off-debug_objects_enabled-from-debug_objects_oom.patch