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Howlett" Cc: "David Hildenbrand (Arm)" , Suren Baghdasaryan , Andrew Morton , Vlastimil Babka , Jann Horn , Pedro Falcato , Shakeel Butt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/task_mmu: fix missed VMAs when reading /proc/PID/maps and friends Message-ID: References: <20261025-per_vma_maps-v1-1-c4eec45b9387@kernel.org> <8c5a8fb7-233e-4433-af45-b67cb2528b60@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: C55C6C0002 X-Stat-Signature: ory9athiz3xpj77zdgi1ojh5myb5h4mp X-Rspam-User: X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1793037909-622889 X-HE-Meta: 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 sJV3CwdW 67n5GSehrnUkyf5d5aKv5VCIY09MbpwYed2tIZCAzv6DoIB3giT4nAIwLR++33mBGs0yV8oB4XxfTLgDd/Fl6W207jPgzjbwZm6I/JSnEzXGhwdL4xhVLSGJ0MIGpcmU2TaBJ0asFS7o6tGZumhY62d1CD0maJkYwJ+RKjEEJZyvFPH9SaWInka2Kb2oYNZSp+rcTN/P3bFCT1VIn2dJpg/w6pPSjQ+xPudvpxontEQ15SGalmfhGLanFFTNNU0zP23uUNq1bzEr1tgNFrK2la5osDjQr7IcDz1pga38E+Z1ioE4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Oct 26, 2026 at 02:01:47PM -0400, Liam R. Howlett wrote: > On 26/10/26 05:26PM, Lorenzo Stoakes (ARM) wrote: > > On Mon, Oct 26, 2026 at 06:19:18PM +0100, David Hildenbrand (Arm) wrote: > > > >> + /* > > > >> + * No lock was held since the last call, so the iterator's cached range > > > >> + * may no longer be valid. Always restart by address. > > > >> + * > > > >> + * The vma_range_is_empty() checks below avoid unnecessary mmap_lock > > > >> + * fallbacks. > > > >> + */ > > > >> + vma_iter_set(vmi, from_addr); > > > > > > > > This is clearly simpler but this unconditional vmi reset is not ideal. > > > > > > Yes, exactly how I ended up where we am right now. > > > > > > I pref my current fix as something to backport that avoids performance changes. > > > > > > If you two disagree, please take it over and drag it over the finishing line in > > > a timely manner. > > > > > > I wasted enough of my weekend with this over-enginered piece of software. (had > > > to change one word before sending, can you guess which :P ) > > > > No problem, will take over. > > > > Just a follow-up, another option: the vma iterator can check the > previous end from vm_end and set the maple state to the range of the > current vma if they disagree. Using the set_range() and not > __set_range(), so the next walk will be a new walk immediately. Ack, as discussed will give that a go and see how it looks taking on board Suren's feedback also! :) -- Cheers, Lorenzo