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b=t5NMGNExCtSd54JUoQ3qnl7voa2g+twGcVcnFZU/PS9I2YOA4Id/TaHnMAKC+iN5M wPhhPc0QPozR1jDPPikyTq09o6v0SWp2Mp7+ufJ+2YQgDOpOJ02dwWjIW9pcvHRabD +Dqb+B3aq/0RCQfGwJeLKWgb83t/YH9Krned8rKGBxz7Kn1Prelotw28wszem76WHi 23S3wZ4CZaRq6FhF6OouBIIl2FaM1NXb+FRderwJ35YjB9PIWQY91i4HWJxHzK7oEY CDOfjMc3xPVWbPHj/ll9LuYaP2CxFu7OROpM7tpjN7jsvhIM/tG77GdUiHIoKFnBg9 SbND62Ma8llSQ== Message-ID: <98480065-e988-477f-ba37-f9521e4aecbb@kernel.org> Date: Mon, 2 Mar 2026 09:00:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/vmscan: restore allowed mask in alloc_demote_folio() To: Bing Jiao , linux-mm@kvack.org Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-kernel@vger.kernel.org References: <20260302070351.3465439-1-bingjiao@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260302070351.3465439-1-bingjiao@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B4FE54000F X-Stat-Signature: a9zksyp7dfou75h6oaojs8a63aqma8an X-Rspam-User: X-HE-Tag: 1772438413-922023 X-HE-Meta: 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 fgsmX716 BeV0Wn0ydgNFc8hYycn7WD4p0Rb4iXWvyye83RTjar2DUakzzOY6FzWUTyKPbj0GfSB6iMChUOiLnVu67oSw4iZTSXtifS4P7roVFb0SozOp8PTgWF9VyB+1GyRNK8DMIn/vCkmkvCdDXkn6njvA1l1HNY/ZsiLYh43FfBDurHKQFJhRyClqMTPdbk3orz0ZM9l7aQMU1IjnoBaosi9Ar8ZbMVpqYXk9c+isrcVRLSRkZLz/36DOl0uu4SU6we3+Oazma4EmOOv3iwGU+whESDpiZ+PnIVEPBAKyLuNyirKeyZqM4IAYfQNNkeLE5LBAlJvda8B/Kuvj/Q2zRk2GB3TDJEkjZ/VFw3qTy5zkfPX7ViWk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/2/26 08:03, 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, restore the mtc->nmask to its original allowed > nodemask after the first allocation. > That would be Fixes: 320080272892 ("mm/demotion: demote pages according to allocation fallback order") ? > Signed-off-by: Bing Jiao > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index cbffc0a27824..b42abd17aee7 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -985,11 +985,11 @@ static struct folio *alloc_demote_folio(struct folio *src, > mtc->nmask = NULL; > mtc->gfp_mask |= __GFP_THISNODE; > dst = alloc_migration_target(src, (unsigned long)mtc); > + mtc->nmask = allowed_mask; > if (dst) > return dst; > > mtc->gfp_mask &= ~__GFP_THISNODE; > - mtc->nmask = allowed_mask; > > return alloc_migration_target(src, (unsigned long)mtc); > } > -- > 2.53.0.473.g4a7958ca14-goog > Maybe we should just not touch the original mtc? diff --git a/mm/vmscan.c b/mm/vmscan.c index de62225b381a..f07716e5389e 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -985,9 +985,9 @@ static void folio_check_dirty_writeback(struct folio *folio, static struct folio *alloc_demote_folio(struct folio *src, unsigned long private) { + struct migration_target_control *mtc, target_nid_mtc; struct folio *dst; nodemask_t *allowed_mask; - struct migration_target_control *mtc; mtc = (struct migration_target_control *)private; @@ -1001,15 +1001,12 @@ static struct folio *alloc_demote_folio(struct folio *src, * a demotion of cold pages from the target memtier. This can result * in the kernel placing hot pages in slower(lower) memory tiers. */ - mtc->nmask = NULL; - mtc->gfp_mask |= __GFP_THISNODE; - dst = alloc_migration_target(src, (unsigned long)mtc); + target_nid_mtc = *mtc; + target_nid_mtc.nmask = NULL; + target_nid_mtc.gfp_mask |= __GFP_THISNODE; + dst = alloc_migration_target(src, (unsigned long)&target_nid_mtc); if (dst) return dst; - - mtc->gfp_mask &= ~__GFP_THISNODE; - mtc->nmask = allowed_mask; - return alloc_migration_target(src, (unsigned long)mtc); } -- Cheers, David