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[109.81.87.110]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48e702f48a8sm177455525e9.15.2026.05.11.05.33.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 05:33:09 -0700 (PDT) Date: Mon, 11 May 2026 14:33:08 +0200 From: Michal Hocko To: Muchun Song Cc: Andrew Morton , Vlastimil Babka , linux-mm@kvack.org, Suren Baghdasaryan , Brendan Jackman , Johannes Weiner , Zi Yan , zihan zhou <15645113830zzh@gmail.com>, yaowenchao , linux-kernel@vger.kernel.org, muchun.song@linux.dev Subject: Re: [PATCH] mm/page_alloc: Fix zone reserve update serialization Message-ID: References: <20260511120409.2264209-1-songmuchun@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260511120409.2264209-1-songmuchun@bytedance.com> On Mon 11-05-26 20:04:09, Muchun Song wrote: > Serialize lowmem reserve and watermark updates with the same lock so > calculate_totalreserve_pages() cannot observe partially updated zone > reserve state. Could you describe the problem you are facing? > 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); > } > > +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); > > - spin_lock(&lock); > - __setup_per_zone_wmarks(); > - spin_unlock(&lock); > + scoped_guard(spinlock_irqsave, &zone_reserve_lock) > + __setup_per_zone_wmarks(); > > /* > * The watermark size have changed so update the pcpu batch > > base-commit: e98d21c170b01ddef366f023bbfcf6b31509fa83 > -- > 2.54.0 -- Michal Hocko SUSE Labs