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Thu, 15 Oct 2026 04:34:10 +0000 X-Mizu-Trace-ID: b288e4c6ce06f05c X-Migadu-Flow: FLOW_OUT From: Lance Yang To: kas@kernel.org Cc: akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, usama.arif@linux.dev, vbabka@kernel.org, jannh@google.com Subject: Re: [PATCH v5 1/9] mm/khugepaged: drop redundant mm_struct pin in madvise_collapse() Date: Thu, 15 Oct 2026 12:34:04 +0800 Message-ID: <20261015043404.57470-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261014171145.3292736-2-kas@kernel.org> References: <20261014171145.3292736-2-kas@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: eenbw8da3fughrmsrbw4onuygjo8js3t X-Rspamd-Queue-Id: 88E1020008 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1792038852-764797 X-HE-Meta: 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 XDCcr3xS ZyRWRoV/Xn+FPmaQL0bi3sv5wzTKgvjc+X+odpPKCGx7qy/GYws6IyijuD2Kc1GaPYSGRIso0p2vWWDhVB62XKG0TuFtfipt2sQbaiTpsMD6qo+NKczJn2MEgCAqjENYNWd03TqztmVMRLeNeNvFR6X6tHMFXTbFodBbPYxnyWoJazKiwpAFSt94z302/UumG8OtdAmi8v5of42Kv8NaqOtDfnFc5mV2FCMOSK/0uiIwMLNZGjWPwo566OgBP4vpWKg+CS2cu878i67hxL9AV51aY89OsRkyPl075dGlMwBNQyLJYkMvUn1qsnFuX9sPYfsseVDghHZSQ7lT7xzO5b375acTdnWfb9y49 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Oct 14, 2026 at 06:11:34PM +0100, Kiryl Shutsemau (Meta) wrote: >madvise_collapse() holds an mmgrab() reference across its work. It is >redundant. Every caller already holds mm_users: > > - madvise(2) works on current->mm, which lives as long as the task is in > the syscall; > - process_madvise(2) reaches a remote mm through mm_access(), which takes > an mm_users reference and holds it until the syscall returns; > - io_uring passes current->mm; > - DAMON takes one with get_task_mm() and drops it after the call. > >Drop the mmgrab()/mmdrop() pair. > >Assisted-by: LLM >Acked-by: David Hildenbrand (Arm) >Reviewed-by: Zi Yan >Reviewed-by: Baolin Wang >Signed-off-by: Kiryl Shutsemau (Meta) >--- Reviewed-by: Lance Yang