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Tue, 16 Dec 2025 22:05:05 -0800 (PST) Received: from localhost ([2a03:2880:25ff:4d::]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-64477db6476sm8629460d50.20.2025.12.16.22.05.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Dec 2025 22:05:05 -0800 (PST) From: Joshua Hahn To: Andrew Morton Cc: Daniel Palmer , Guenter Roeck , Brendan Jackman , Johannes Weiner , Michal Hocko , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH] mm/page_alloc: restore 0-handling to zone_set_pageset_high_and_batch Date: Tue, 16 Dec 2025 22:05:03 -0800 Message-ID: <20251217060505.681923-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: E8CB34000A X-Stat-Signature: nbkq3wsijczokwf3uymyr3qhzaq3t67x X-Rspam-User: X-HE-Tag: 1765951506-557841 X-HE-Meta: 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 fFBNCSzJ 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Commit 2783088ef24e ("mm/page_alloc: prevent reporting pcp->batch = 0") moved the error handling (0-handling) of zone_batchsize from its callers to inside the function. However, the commit left out the error handling for the NOMMU case, leading to deadlocks on NOMMU systems. Since in the NOMMU case the reported-to-user batchsize should still be 0, we would only like the error handling to exist in the callsites that set the internal value for the zone (i.e. zone_set_pageset_high_and_batch). Restore max(1, zone_batchsize(zone)) to the callsite to prevent errors on NOMMU systems. Fixes: 2783088ef24e ("mm/page_alloc: prevent reporting pcp->batch = 0") Reported-by: Daniel Palmer Closes: https://lore.kernel.org/linux-mm/CAFr9PX=_HaM3_xPtTiBn5Gw5-0xcRpawpJ02NStfdr0khF2k7g@mail.gmail.com/ Reported-by: Guenter Roeck Closes: https://lore.kernel.org/all/42143500-c380-41fe-815c-696c17241506@roeck-us.net/ Signed-off-by: Joshua Hahn --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 822e05f1a964..10c1297fd3ea 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6045,7 +6045,7 @@ static void zone_set_pageset_high_and_batch(struct zone *zone, int cpu_online) { int new_high_min, new_high_max, new_batch; - new_batch = zone_batchsize(zone); + new_batch = max(1, zone_batchsize(zone)); if (percpu_pagelist_high_fraction) { new_high_min = zone_highsize(zone, new_batch, cpu_online, percpu_pagelist_high_fraction); base-commit: 40fbbd64bba6c6e7a72885d2f59b6a3be9991eeb -- 2.47.3