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([2a02:6b67:d751:7400:c2b:f323:d172:e42a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-381ed97c6b6sm11081641f8f.24.2024.11.10.13.22.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 10 Nov 2024 13:22:51 -0800 (PST) Message-ID: <683dc253-8dd0-4990-944c-e20a3f79074c@gmail.com> Date: Sun, 10 Nov 2024 21:22:50 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH hotfix] mm/thp: fix deferred split queue not partially_mapped: fix To: Hugh Dickins , Andrew Morton Cc: Zi Yan , Yang Shi , Wei Yang , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Johannes Weiner , Baolin Wang , Barry Song , Kefeng Wang , Ryan Roberts , Nhat Pham , Chris Li , Shakeel Butt , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <81e34a8b-113a-0701-740e-2135c97eb1d7@google.com> <6fcaaa72-4ef6-ebda-cf37-b6f49874d966@google.com> <3c995a30-31ce-0998-1b9f-3a2cb9354c91@google.com> Content-Language: en-US From: Usama Arif In-Reply-To: <3c995a30-31ce-0998-1b9f-3a2cb9354c91@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Stat-Signature: x47mo615ryg4876zx653kbjnr8mincd4 X-Rspamd-Queue-Id: 0164E180008 X-Rspam-User: X-HE-Tag: 1731273733-862787 X-HE-Meta: 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 7jcJQ5+V 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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 10/11/2024 21:11, Hugh Dickins wrote: > Though even more elusive than before, list_del corruption has still been > seen on THP's deferred split queue. > > The idea in commit e66f3185fa04 was right, but its implementation wrong. > The context omitted an important comment just before the critical test: > "split_folio() removes folio from list on success." In ignoring that > comment, when a THP split succeeded, the code went on to release the > preceding safe folio, preserving instead an irrelevant (formerly head) > folio: which gives no safety because it's not on the list. Fix the logic. > > Fixes: e66f3185fa04 ("mm/thp: fix deferred split queue not partially_mapped") > Signed-off-by: Hugh Dickins Acked-by: Usama Arif > --- > mm/huge_memory.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 03fd4bc39ea1..5734d5d5060f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3790,7 +3790,9 @@ static unsigned long deferred_split_scan(struct shrinker *shrink, > * in the case it was underused, then consider it used and > * don't add it back to split_queue. > */ > - if (!did_split && !folio_test_partially_mapped(folio)) { > + if (did_split) { > + ; /* folio already removed from list */ > + } else if (!folio_test_partially_mapped(folio)) { > list_del_init(&folio->_deferred_list); > removed++; > } else {