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b=u2PKA6OpAxboIzAOfCcmy+G38IYeBYHiSzDBnTwnqDXel41RKhECx7XETmIzP9vt6 DZr9207euHyJHUzt5C6WbVacT2DDye1Alml7Gdn8K4KXbH/0IAwGCRYb98PFLCcZ4I zM/iu91PB6qE4p8kj1P1+LuZVa4rHssBAe5a7bX5pL6NWMikW8KB51v4px0krgUmDD ach1EGskWjUlfa/Yc4d2yEbay344J8v3Wmzfbj7VEyQ2Skh7XX3HBrXXZmh21o6JKY +AhVc+0nzM2znyP+1aJeB6aPx6/vGVgoPGmtGUhfahoTlyXI6nbVUBvb+5jZhFDt82 jznVIHjdPOIBQ== Message-ID: <94297332-45d8-4b8a-b368-ad66e128f273@kernel.org> Date: Tue, 3 Mar 2026 10:01:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/vmscan: fix unintended mtc->nmask mutation in alloc_demote_folio() To: Bing Jiao Cc: akpm@linux-foundation.org, axelrasmussen@google.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@kernel.org, shakeel.butt@linux.dev, weixugc@google.com, yuanchu@google.com, zhengqi.arch@bytedance.com References: <20260302070351.3465439-1-bingjiao@google.com> <20260303052519.109244-1-bingjiao@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 79225A0005 X-Stat-Signature: c1d1mrnxoewhc4iigarapg8f5z5m6wt1 X-Rspam-User: X-HE-Tag: 1772528499-124651 X-HE-Meta: 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 a1/SALrw K1Kn8OJo33ffo9xYuDE6rcf4d/sMMEEa22JFTiF3nX4xPwolhR12zxFF1RF1PXI+EVCD8T5pVPEmFzgX5NPFwvn2lSK73IAXvqImWPX58zJkI6UXFic1H0fhGWnOVpwPxOm3YbkQ2douSWXEAQX7MpIOHaAIRdl91cDG6VQiv+lC+Xz0jEalQsitPqwksRjSprDEqqAR5Wff5zDy8c8eGphf2Eh3YISQZbdrlsf3/uqliycJgxQ7yOER164qwPbDj3lRB7uNvMIdJVgOlUC2ldY4bktzOnzrSp3ZjeDTuP0Ag89vpAPv+VNxOPC3Zo4TRVkfpWSJ6STdK8uLZpoW01Pp663LsZ1pq5FGwn4iDClBJGCsAuWRJWFG34GdXzpl+OEENBABMMXsOUy0HFh/VW+6SwA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/3/26 06:25, Bing Jiao wrote: > In alloc_demote_folio(), mtc->nmask is set to NULL for the first > allocation. If that succeeds, it returns without restoring mtc->nmask > to allowed_mask. For subsequent allocations from the migrate_pages() > batch, mtc->nmask will be NULL. If the target node then becomes full, > the fallback allocation will use nmask = NULL, allocating from any > node allowed by the task cpuset, which for kswapd is all nodes. > > To address this issue, use a local copy of the mtc structure with > nmask = NULL for the first allocation attempt specifically, ensuring > the original mtc remains unmodified. > > Fixes: 320080272892 ("mm/demotion: demote pages according to allocation fallback order") > Signed-off-by: Bing Jiao > --- > mm/vmscan.c | 14 +++++--------- > 1 file changed, 5 insertions(+), 9 deletions(-) Acked-by: David Hildenbrand (Arm) -- Cheers, David