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Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , Mike Rapoport , Nadav Amit , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Subject: Re: [PATCH v7 3/4] fs/proc/task_mmu: Implement IOCTL to get and/or the clear info about PTEs To: Peter Xu References: <20230109064519.3555250-1-usama.anjum@collabora.com> <20230109064519.3555250-4-usama.anjum@collabora.com> <31b71791-66b0-c2d8-81da-e17eff5ffbe8@collabora.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 59zkfcr1ror1jeu6nnb1w58ge341z893 X-Rspam-User: X-Rspamd-Queue-Id: 05AEE140010 X-Rspamd-Server: rspam06 X-HE-Tag: 1674743586-158868 X-HE-Meta: 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 Yo90R5RU KJoQGzTzyGCDFtrn1TOr4BXCDP7rs3JNJ4LhCQAfoINHYzcU5EhWmymAWsymhheq7TPEt2WeHlJkunEnIkTL45g1eTPa7vsuqkVOgX5WviFXMyVvGjcz8fg9ifl5cJCvSMjLXg5tXuwjFWdNV+V0WyhS0ZDdCEGKL8qoVL7Y2Vsf2letOhIVWxiTTaE8SHB+Bd2u9xlHyz/fu2iQMSZ+dQsRfpq5G8ouKq1sVYcI8vg5CEWpRB+usPPBDwqJpAw2Q7mqy6hazJM8AHT8= 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: On 1/24/23 10:30 PM, Peter Xu wrote: > On Mon, Jan 23, 2023 at 05:18:13PM +0500, Muhammad Usama Anjum wrote: >>>> + if (IS_GET_OP(p) && p->max_pages && (p->found_pages == p->max_pages)) >>>> + return -ENOSPC; >>> >>> This is the function to test "whether the walker should walk the vma >>> specified". This check should IIUC be meaningless because found_pages >>> doesn't boost during vma switching, while OTOH your pmd walker fn should do >>> proper check when increasing found_pages and return -ENOSPC properly when >>> the same condition met. That should be enough, IMHO. >> This check is needed in case we want to abort the walk at once. We return >> negative value from here which aborts the walk. Returning negative value >> from pmd_entry doesn't abort the walk. So this check is needed in the >> test_walk. > > Why? What I see locally is (walk_pmd_range): > > if (ops->pmd_entry) > err = ops->pmd_entry(pmd, addr, next, walk); > if (err) > break; Sorry, mistake on my part. I'll correct it in next version (v9). > > Thanks, > -- BR, Muhammad Usama Anjum