linux-kernel - [PATCH] mm/page_alloc: Fix memory accept before watermarks gets initialized

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Message-ID: <20250310082855.2587122-1-kirill.shutemov@linux.intel.com>
Date: Mon, 10 Mar 2025 10:28:55 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mike Rapoport <rppt@...nel.org>,
	David Hildenbrand <david@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Tom Lendacky <thomas.lendacky@....com>,
	"Kalra, Ashish" <ashish.kalra@....com>,
	Rick Edgecombe  <rick.p.edgecombe@...el.com>,
	linux-mm@...ck.org,
	linux-coco@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Farrah Chen <farrah.chen@...el.com>
Subject: [PATCH] mm/page_alloc: Fix memory accept before watermarks gets initialized

Watermarks are initialized during the postcore initcall. Until then, all
watermarks are set to zero. This causes cond_accept_memory() to
incorrectly skip memory acceptance because a watermark of 0 is always
met.

To ensure progress, accept one MAX_ORDER page if the watermark is zero.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reported-and-tested-by: Farrah Chen <farrah.chen@...el.com>
---
 mm/page_alloc.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 579789600a3c..4fe93029bcb6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7004,7 +7004,7 @@ static inline bool has_unaccepted_memory(void)
 
 static bool cond_accept_memory(struct zone *zone, unsigned int order)
 {
-	long to_accept;
+	long to_accept, wmark;
 	bool ret = false;
 
 	if (!has_unaccepted_memory())
@@ -7013,8 +7013,18 @@ static bool cond_accept_memory(struct zone *zone, unsigned int order)
 	if (list_empty(&zone->unaccepted_pages))
 		return false;
 
+	wmark = promo_wmark_pages(zone);
+
+	/*
+	 * Watermarks have not been initialized yet.
+	 *
+	 * Accepting one MAX_ORDER page to ensure progress.
+	 */
+	if (!wmark)
+		return try_to_accept_memory_one(zone);
+
 	/* How much to accept to get to promo watermark? */
-	to_accept = promo_wmark_pages(zone) -
+	to_accept = wmark -
 		    (zone_page_state(zone, NR_FREE_PAGES) -
 		    __zone_watermark_unusable_free(zone, order, 0) -
 		    zone_page_state(zone, NR_UNACCEPTED));
-- 
2.47.2