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Thu, 18 Dec 2025 00:35:11 -0800 (PST) From: Joshua Hahn To: Guenter Roeck Cc: Andrew Morton , Daniel Palmer , Brendan Jackman , Johannes Weiner , Michal Hocko , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/page_alloc: restore 0-handling to zone_set_pageset_high_and_batch Date: Thu, 18 Dec 2025 00:35:09 -0800 Message-ID: <20251218083510.2462817-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: F3340C0003 X-Stat-Signature: 4izg3z7kfrp1yscxaogmmdobgqarpb9p X-Rspam-User: X-HE-Tag: 1766046913-339857 X-HE-Meta: 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 lbDGnd26 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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 Wed, 17 Dec 2025 08:47:12 -0800 Guenter Roeck wrote: > On Tue, Dec 16, 2025 at 10:05:03PM -0800, 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. > > > > 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 > > For m68k:mcf5208evb boot tests with qemu: > > Tested-by: Guenter Roeck > > Guenter Hello Guenter, thank you so much for spending the time to test my patch! I've gone ahead and took Vlastimil's suggestion, which just returns 1 for zone_batchsize for NOMMU systems. Functionally, it should be the same but I thought it might be best not to carry the tested-by tag over, since the code changed in its implementation. Thank you again for testing the code, and sorry for the bug in the first place. Have a great day! Joshua