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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-2d096a20194sm3745837fac.30.2025.04.16.22.36.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 22:36:24 -0700 (PDT) Date: Wed, 16 Apr 2025 22:36:22 -0700 (PDT) From: Hugh Dickins To: David Hildenbrand cc: Gavin Guo , linux-mm@kvack.org, akpm@linux-foundation.org, willy@infradead.org, ziy@nvidia.com, linmiaohe@huawei.com, hughd@google.com, revest@google.com, kernel-dev@igalia.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: fix dereferencing invalid pmd migration entry In-Reply-To: <27d13454-280f-4966-b694-d7e58d991547@redhat.com> Message-ID: <6787d0ea-a1b9-08cf-1f48-e361058eec20@google.com> References: <20250414072737.1698513-1-gavinguo@igalia.com> <27d13454-280f-4966-b694-d7e58d991547@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Wed, 16 Apr 2025, David Hildenbrand wrote: > > Why not something like > > struct folio *entry_folio; > > if (folio) { > if (is_pmd_migration_entry(*pmd)) > entry_folio = pfn_swap_entry_folio(pmd_to_swp_entry(*pmd))); > else > entry_folio = pmd_folio(*pmd)); > > if (folio != entry_folio) > return; > } My own preference is to not add unnecessary code: if folio and pmd_migration entry, we're not interested in entry_folio. But yes it could be written in lots of other ways. Hugh