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bh=1h7SuxIdXP1BrmLiSW0TA0Y4x+A0dQHqIxOY0fZWzgw=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793706391; v=1; x=1794311191; b=M5WQx64W3OrKv3IrbfaaaUU8t9LBurF+lIi1NsZf+TH86Tb8kzcQtOfRinqCLkp6vbJeJkjn Wdwp+SEY7bV+SCApfixGc5g2PSWIhjsr5o8DnWz2b+eULeX3U8KrowNWRCDh9p9CW2PdjVmXutk fgWn2GKcQL5AnmV3qr19TWzU= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 4c5c651460189e35; Tue, 03 Nov 2026 11:46:31 +0000 X-Mizu-Trace-ID: 4c5c651460189e35 X-Migadu-Flow: FLOW_OUT From: Lance Yang To: david@kernel.org Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, ljs@kernel.org, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, kees@kernel.org, peterz@infradead.org, jannh@google.com, pfalcato@suse.de, hughd@google.com, pasha.tatashin@soleen.com, pratyush@kernel.org, willy@infradead.org, jack@suse.cz, ziy@nvidia.com, lance.yang@linux.dev, riel@surriel.com, harry@kernel.org, apopple@nvidia.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, jhubbard@nvidia.com, peterx@redhat.com, will@kernel.org, aneesh.kumar@kernel.org, npiggin@gmail.com, osalvador@suse.de, minchan@kernel.org, muchun.song@linux.dev, xu.xin@linux.dev, chengming.zhou@linux.dev, chrisl@kernel.org, shikemeng@huaweicloud.com, nphamcs@gmail.com, youngjun.park@lge.com, gourry@gourry.net, joshua.hahnjy@gmail.com, rakie.kim@sk.com, ying.huang@linux.alibaba.com, jgg@ziepe.ca, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, mason@kernel.org, stable@vger.kernel.org, usama.anjum@arm.com Subject: Re: [PATCH v3 41/47] mm/ksm: check large swap-cache folios before mapping them Date: Tue, 3 Nov 2026 19:46:26 +0800 Message-ID: <20261103114626.15764-1-lance.yang@linux.dev> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20261031-fixes_core-v3-41-d6437171ecc3@kernel.org> References: <20261031-fixes_core-v3-41-d6437171ecc3@kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Sat, Oct 31, 2026 at 10:40:10AM +0100, David Hildenbrand (Arm) wrote: >From: Chris Mason > >KSM folios are always small, but their shared swap slots can be read >back as part of a large folio in the swap cache. ksm_might_need_to_copy() >skips large folios, so another process can map a page with an incompatible >anon_vma or page index. Reverse mapping then cannot find the new >mapping, preventing migration or reclaim. > >Apply the same compatibility checks to large folios as to small ones. >Pass the page corresponding to the swap entry and copy only that page >when necessary. In do_swap_page()'s copy path, decrement only that slot's >swap count, because the source swap-cache folio can now be large. > >Fix generated by an LLM and sent by Chris Mason in private. > >Fixes: f1879e8a0c60 ("mm, swap: never bypass the swap cache even for SWP_SYNCHRONOUS_IO") >Cc: stable@vger.kernel.org >Signed-off-by: Chris Mason >Reviewed-by: Lorenzo Stoakes (ARM) >Tested-by: Muhammad Usama Anjum >Signed-off-by: David Hildenbrand (Arm) >--- LGTM1 Reviewed-by: Lance Yang