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Received: from 30.74.144.134(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XEbHbqg_1794469212 cluster:ay36) by smtp.aliyun-inc.com; Thu, 12 Nov 2026 15:40:13 +0800 Message-ID: Date: Thu, 12 Nov 2026 15:40:11 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] fs/proc/task_mmu: don't read young/dirty from a non-present PMD in smaps To: Usama Arif , Andrew Morton , apopple@nvidia.com, byungchul@sk.com, david@kernel.org, gourry@gourry.net, jannh@google.com, joshua.hahnjy@gmail.com, liam@infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, matthew.brost@intel.com, mhocko@suse.com, pfalcato@suse.de, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, kas@kernel.org, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, kernel-team@meta.com, Nico Pache , ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev Cc: stable@vger.kernel.org References: <20261111113904.650722-1-usama.arif@linux.dev> <20261111113904.650722-3-usama.arif@linux.dev> From: Baolin Wang In-Reply-To: <20261111113904.650722-3-usama.arif@linux.dev> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: ppaqgkkfshc3mykoifanwh8bbehtk36n X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-19.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: CC42380003 X-HE-Tag: 1794469218-120879 X-HE-Meta: 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 y4qs34u0 m0JQXs7lJfHhOJ38ur5ozQM1PAhyxH/VSgDOQc0B94lw0DBpmkko/FNO8scNwoi5iII+e3Fjm0wLgGpwfk1NiQ47iW637V1D6p/ZNnygLzzVGnjwWHDnlqcVDTo0r7DO+IkBFkMly6qWkzT5OpzuYTpSEKM4CekU8LWy9pi9Tjqwdh9uKRybi49nWIi9yFbSsSVWjhdl8+6GS0hukCsiDNZXAFttTjci1gii1mkn2mPckhQKIYzUKipzqWe9gDeFvVxxRj82GgIm1YquYo0jPr/x3XxF0iQgbMvzxYydCqAGwHe0Tu3eaGvXSPSMondIAwqwTtM/AFeKuJ0ivC1cpw79B3O6UbkZ6uHqocC5Sg638HP6yxgwV5Dh+juVCGnnsP+VrnoWlwVK6OdDkBayrhUN8xo8zdmpSKA/4dq3IFMNSrYTWxuQMEAFhpTkItGhujkYSTFZ4jZqAcIzb6DWlBMcT5rw7v6c13shL 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 11/11/26 7:38 PM, Usama Arif wrote: > smaps_pmd_entry() passes pmd_young(*pmd) and pmd_dirty(*pmd) to > smaps_account() for every PMD, including migration and device-private > entries, where those bits hold part of the swap offset rather than > accessed/dirty state. smaps_pte_entry() only reads them when the entry > is present. > > On x86_64 the offset is stored inverted across bits 9-58, which overlap > _PAGE_SAVED_DIRTY, so pmd_dirty() returns garbage: a clean 2MB > device-private mapping is accounted as 2048 kB dirty, and lazyfree > accounting is suppressed. pgtable_64.h also warns that the hardware can > set the accessed and dirty bits on non-present entries by mistake. > > Only read the bits when the PMD is present. > > Fixes: c94b6923fa0a ("/proc/PID/smaps: Add PMD migration entry parsing") > Cc: stable@vger.kernel.org > Signed-off-by: Usama Arif > --- Make sense to me. Reviewed-by: Baolin Wang