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Thu, 18 Dec 2025 11:23:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id GeYNOz3kQ2k+ZQAAD6G6ig (envelope-from ); Thu, 18 Dec 2025 11:23:41 +0000 Message-ID: Date: Thu, 18 Dec 2025 12:23:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/page_alloc: Report 1 as zone_batchsize for !CONFIG_MMU Content-Language: en-US To: Joshua Hahn , Andrew Morton Cc: Daniel Palmer , Guenter Roeck , Brendan Jackman , Johannes Weiner , Michal Hocko , Suren Baghdasaryan , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com References: <20251218083200.2435789-1-joshua.hahnjy@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20251218083200.2435789-1-joshua.hahnjy@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: tjiw8preqoos3npso84tsbwa6seoeapu X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: D9860C0008 X-Rspam-User: X-HE-Tag: 1766057023-418152 X-HE-Meta: U2FsdGVkX18fvIsNgN0M5mL9rqDibHfNMRy+NhWHeZHkP6B303ZDmixtw6JW0AWPKUHqCrdAKlkxHpumjsLaTWV6nctOA6PFj8g+lVdzXd8gETTpEY0TkZklwVSBS/zjMZ3S1xUu2XLj/PrQqFFPIfzviZbrzU19+JOD/BrR3Yo/KHskIbIaemoUuw+q5AmvDjLbzzXl8TX8m9kO/S4R6LVJnrEXc1TSUHI6Pe6AP3ajC1iTrG+Iyd8eutKq9+2MD7cg1EF7tkWURdy35e+YKwSt+5wk4N48Xj5kzTIi3VLXz6mLaQ5ItJuFSnUtSaUGUmm8Nxegy2GKM+2XFI1RyjSHb3i40r3cWSaRuuLZ4Bu7iiy+FP+fkb/dcV7Z5KYdyMwXyrPtFSWyiaw3wRxJZ53wOxeMNNHc7/Px8uKrcUhcis1lG0S4IdyT86X7PmEdZn6xi79X9vNW3kixkGja0PcZFEuw3uUU8PIeKxfYUucJzqX4gyNnFRXtte33oHCjdio2VxdOqXaOxAQHOT+vpuxa8TUfxIPoGQWayiBRUKHhJbOZYh+XKznLxIW/Ruxag43gRFs/F78S9c3MzF5lA3//NtDvBxh7YYRyzj9mAhEM/JRphqBX3TGxaGCfLl/J8/6kMwF2t/IJ5AZa9+VW9iCacYor/lQ786mQT2h8ttGtaXR8QrOtlT+CRmcVbotEe1BruRxAgp82wTdZvOELK7miH/nAUBtgvjVIWvtM/wUbBAhBqf+TOHbCFh++U52aVsfOrWwSN19Grel/RVX4DOqlKPT939FKJ7xaaydhbrz9up0qNkHAHCJ1BA0nT9+ikM470mB9vMf+FH7vruz5vj1IHhgxPCd/dcjwk66ukOLvfspLf0BackO8drpluKz9xrA/LfWJvrYAdtSRMdGm2eMhjioC7Ygm9H6wdEcr6AN8Chmogh3Q4+C27UIfF+RZzZK9RMYw111W+Lxb0Ep v4xChGQP 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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: On 12/18/25 09:31, Joshua Hahn wrote: > 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. > > For NOMMU systems, return 1 instead of 0 for zone_batchsize, which restores > the previous deadlock-free behavior. > > There is no functional difference expected with this patch before commit > 2783088ef24e, other than the pr_debug in zone_pcp_init now printing out > 1 instead of 0 for zones in NOMMU systems. Not only is this a pr_debug, > the difference is purely semantic anyways. > > 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 Reviewed-by: Vlastimil Babka > --- > v1 --> v2: > - Instead of restoring max(1, zone_batchsize(zone)), just return 1 for NOMMU > systems since this is simpler and only affects a single pr_debug. > 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..977cbf20777d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5924,7 +5924,7 @@ static int zone_batchsize(struct zone *zone) > * recycled, this leads to the once large chunks of space being > * fragmented and becoming unavailable for high-order allocations. > */ > - return 0; > + return 1; > #endif > } > > > base-commit: 40fbbd64bba6c6e7a72885d2f59b6a3be9991eeb