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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-44f9cda773csm36770541cf.77.2024.07.22.14.17.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jul 2024 14:17:31 -0700 (PDT) Date: Mon, 22 Jul 2024 17:17:28 -0400 From: Peter Xu To: "Liam R. Howlett" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Alex Williamson , Jason Gunthorpe , Al Viro , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Kirill A . Shutemov" , x86@kernel.org, Yan Zhao , Kevin Tian , Pei Li , David Hildenbrand , David Wang <00107082@163.com>, Bert Karwatzki , Sergey Senozhatsky Subject: Re: [PATCH] mm/x86/pat: Only untrack the pfn range if unmap region Message-ID: References: <20240712144244.3090089-1-peterx@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B9B351A000C X-Stat-Signature: nhca9s4t5bzh4wr6ekgza7rj718nfb5g X-HE-Tag: 1721683055-837173 X-HE-Meta: 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 HxQ5JJ0H 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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 Mon, Jul 22, 2024 at 04:22:45PM -0400, Liam R. Howlett wrote: > The problem report from [2] and [3] is that we are getting to a call > path that includes unmap_single_vma() without the mmap lock. This patch > fails to address that issue, it only takes the caller with the assert > out of the call path. > > Removing the function with the lock check doesn't fix the locking issue. > If there is no locking issue here, please state the case in the commit > log as you feel it is safe to use a vma pointer without the mmap_lock > held. Could you please state why there's a locking issue, and why this patch (of a x86 PAT specific issue...) would need any documentation on that? I thought it was pretty common that file truncation (or anything similar) does a file rmap walk over vmas that mapping this file, and vmas need to be alive during the rmap walk, no? Thanks, -- Peter Xu