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Mon, 11 May 2026 05:04:42 -0700 (PDT) From: Muchun Song To: Andrew Morton , Vlastimil Babka , linux-mm@kvack.org Cc: Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , zihan zhou <15645113830zzh@gmail.com>, yaowenchao , linux-kernel@vger.kernel.org, Muchun Song , muchun.song@linux.dev Subject: [PATCH] mm/page_alloc: Fix zone reserve update serialization Date: Mon, 11 May 2026 20:04:09 +0800 Message-ID: <20260511120409.2264209-1-songmuchun@bytedance.com> X-Mailer: git-send-email 2.54.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Serialize lowmem reserve and watermark updates with the same lock so calculate_totalreserve_pages() cannot observe partially updated zone reserve state. Fixes: 9726891fe753 ("mm: page_alloc: fix missed updates of lowmem_reserve = in adjust_managed_page_count") Signed-off-by: Muchun Song --- mm/page_alloc.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3a56825a7fc5..0989067da588 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6384,6 +6384,8 @@ static void calculate_totalreserve_pages(void) trace_mm_calculate_totalreserve_pages(totalreserve_pages); } =20 +static DEFINE_SPINLOCK(zone_reserve_lock); + /* * setup_per_zone_lowmem_reserve - called whenever * sysctl_lowmem_reserve_ratio changes. Ensures that each zone @@ -6394,6 +6396,8 @@ static void setup_per_zone_lowmem_reserve(void) { struct pglist_data *pgdat; enum zone_type i, j; + + guard(spinlock_irqsave)(&zone_reserve_lock); /* * For a given zone node_zones[i], lowmem_reserve[j] (j > i) * represents how many pages in zone i must effectively be kept @@ -6509,11 +6513,9 @@ static void __setup_per_zone_wmarks(void) void setup_per_zone_wmarks(void) { struct zone *zone; - static DEFINE_SPINLOCK(lock); =20 - spin_lock(&lock); - __setup_per_zone_wmarks(); - spin_unlock(&lock); + scoped_guard(spinlock_irqsave, &zone_reserve_lock) + __setup_per_zone_wmarks(); =20 /* * The watermark size have changed so update the pcpu batch base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83 --=20 2.54.0