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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id s133-20020a37a98b000000b00706afbdeb01sm1799074qke.8.2023.01.24.09.30.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Jan 2023 09:30:34 -0800 (PST) Date: Tue, 24 Jan 2023 12:30:32 -0500 From: Peter Xu To: Muhammad Usama Anjum Cc: David Hildenbrand , Andrew Morton , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Andrei Vagin , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov , Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . 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 Message-ID: References: <20230109064519.3555250-1-usama.anjum@collabora.com> <20230109064519.3555250-4-usama.anjum@collabora.com> <31b71791-66b0-c2d8-81da-e17eff5ffbe8@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <31b71791-66b0-c2d8-81da-e17eff5ffbe8@collabora.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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; Thanks, -- Peter Xu