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h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=t9Si7QwppVqej3YsdEFVrKl5GM6emLtHJ1fJ+xuPG01qx9MyQGoGlu2mYP62tv7qt PSqlT3IXnpNLcpyQDo6HlLidTBk37OUeAcPfovTBFwpT4zjtIqYB00vps1Tqc8As8N q2vWJ87LBnRwBmY4iDAJN0mhCTEq+FK8ZU1QrRjA= Date: Mon, 8 Jul 2024 16:04:07 -0700 From: Andrew Morton To: Peter Xu Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zi Yan , Yang Shi , Hugh Dickins , Baolin Wang , Huang Ying , David Hildenbrand Subject: Re: [PATCH] mm/migrate: Putback split folios when numa hint migration fails Message-Id: <20240708160407.a0c51eb11d0403c161d27540@linux-foundation.org> In-Reply-To: <20240708215537.2630610-1-peterx@redhat.com> References: <20240708215537.2630610-1-peterx@redhat.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: co1w93q8a7hpzbszn5r3s76gxsqxki5k X-Rspamd-Queue-Id: 11B8B1C0013 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1720479852-754300 X-HE-Meta: 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 v1wiQuVE w8RKJWx1bReYBxrKanFAvQyCjKfnUQe92T/VXlT/87lISkpfma1VcOLmep5jiixJ22oIvqkvg4dMPkOzmozpTa8lk+vQznqqWWvMcf3pkyoHgtRGjwtMIvdrXDfvkCMDpHQXDYqb/XL484wdbudGaTTfjV3WmFrjGv65LF/mlecF7ngzPfIC2RirhN8C0Yftq6C2DqUusmyw+e8lA7JehcvawKbF2sZQSH66AS31yWmyvJPW6rBv9x5M22w== 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 Mon, 8 Jul 2024 17:55:37 -0400 Peter Xu wrote: > This issue is not from any report yet, but by code observation only. > > This is yet another fix besides Hugh's patch [1] but on relevant code path, > where eager split of folio can happen if the folio is already on deferred > list during a folio migration. > > Here the issue is NUMA path (migrate_misplaced_folio()) may start to > encounter such folio split now even with MR_NUMA_MISPLACED hint applied. > Then when migrate_pages() didn't migrate all the folios, it's possible the > split small folios be put onto the list instead of the original folio. > Then putting back only the head page won't be enough. > > Fix it by putting back all the folios on the list. mm/migrate.c: In function 'migrate_misplaced_folio': mm/migrate.c:2624:13: error: unused variable 'nr_pages' [-Werror=unused-variable] 2624 | int nr_pages = folio_nr_pages(folio); | ^~~~~~~~ Worrisome. Which kernel version was this tested against? > Don't need to copy stable if this can still hit 6.10.. Only smoke tested. Also worrisome. Are we to take an only-smoke-tested patch which doesn't apply to mainline and which doesn't compile on mm-unstable into mainline based on "only smoke tested"?