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Thu, 07 Mar 2024 06:44:15 -0800 (PST) Received: from localhost ([102.222.70.76]) by smtp.gmail.com with ESMTPSA id e3-20020a05600c4e4300b00412ad64cc69sm2974014wmq.29.2024.03.07.06.44.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 Mar 2024 06:44:14 -0800 (PST) Date: Thu, 7 Mar 2024 17:44:11 +0300 From: Dan Carpenter To: Zi Yan Cc: linux-mm@kvack.org Subject: Re: [bug report] mm: huge_memory: enable debugfs to split huge pages to any order Message-ID: <8984dce7-7538-47e6-b770-213e344451ab@moroto.mountain> References: <7dda9283-b437-4cf8-ab0d-83c330deb9c0@moroto.mountain> <4EFF8F91-5B42-4E90-BFBB-FBA8DAAB8301@nvidia.com> <5520C6FB-9ED1-439C-8F61-5BD99B4788E3@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5520C6FB-9ED1-439C-8F61-5BD99B4788E3@nvidia.com> X-Rspamd-Queue-Id: D99EBC001D X-Rspam-User: X-Stat-Signature: a5js4rfezkwsa131tudmhihnz9caq8dh X-Rspamd-Server: rspam01 X-HE-Tag: 1709822656-365547 X-HE-Meta: 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 OOU5QCfJ OjbPAtdBviqnNW6WM7/ESeDNGuWs+6eZrvcNpiTfxMjm6WgPVmfEPaejq+NtTtPqg/xoHiLwpCwe0Qio= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000061, 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 Thu, Mar 07, 2024 at 09:41:17AM -0500, Zi Yan wrote: > On 7 Mar 2024, at 9:31, Dan Carpenter wrote: > > > On Thu, Mar 07, 2024 at 09:20:09AM -0500, Zi Yan wrote: > >> > >> Can you check if the patch below fixes the issue? I checked the inputs from > >> debugfs and also inside split_huge_page_to_list_to_order(). > >> > >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c > >> index a81a09236c16..4d21e57a7d07 100644 > >> --- a/mm/huge_memory.c > >> +++ b/mm/huge_memory.c > >> @@ -3052,6 +3052,9 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list, > >> VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); > >> VM_BUG_ON_FOLIO(!folio_test_large(folio), folio); > >> > >> + if (new_order >= folio_order(folio)) > >> + return -EINVAL; > >> + > >> /* Cannot split anonymous THP to order-1 */ > >> if (new_order == 1 && folio_test_anon(folio)) { > >> VM_WARN_ONCE(1, "Cannot split to order-1 folio"); > > > > From a static analysis perspective I think just this is sufficient? But > > I don't really know the code and don't object to the other parts of > > this path either. > > You are right. The other two changes are in debugfs to avoid unnecessary > folio locking operations. They are more like an optimization. Fantastic. Thanks! regards, dan carpenter