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Sun, 19 Jan 2025 17:31:02 -0800 (PST) Received: from EBJ9932692.tcent.cn ([43.134.20.116]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-21c2ceb7476sm50716265ad.56.2025.01.19.17.30.55 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sun, 19 Jan 2025 17:31:02 -0800 (PST) From: Lance Yang To: akpm@linux-foundation.org Cc: 21cnbao@gmail.com, ryan.roberts@arm.com, dev.jain@arm.com, david@redhat.com, shy828301@gmail.com, ziy@nvidia.com, libang.li@antgroup.com, baolin.wang@linux.alibaba.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, Jason@zx2c4.com, Lance Yang , Mingzhe Yang Subject: [RFC 1/1] mm/madvise: fail MADV_PAGEOUT on VM_DROPPABLE VMA Date: Mon, 20 Jan 2025 09:30:38 +0800 Message-ID: <20250120013038.6657-1-ioworker0@gmail.com> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit MADV_PAGEOUT should fail on VMAs with the VM_DROPPABLE flag. While MADV_PAGEOUT is intended to move anonymous pages to swap, VM_DROPPABLE should not be swapped out. There is an issue where using MADV_PAGEOUT on a VMA with the VM_DROPPABLE flag behaves like MADV_DONTNEED, causing the pages to be dropped. This could break the semantics of MADV_PAGEOUT, IMO. So, let's add a check to detect the VM_DROPPABLE flag before doing MADV_PAGEOUT and returns -EINVAL. Fixes: 9651fcedf7b9 ("mm: add MAP_DROPPABLE for designating always lazily freeable mappings") Signed-off-by: Mingzhe Yang Signed-off-by: Lance Yang --- mm/madvise.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/madvise.c b/mm/madvise.c index 49f3a75046f6..29d0234da8a1 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1263,6 +1263,8 @@ static int madvise_vma_behavior(struct vm_area_struct *vma, case MADV_COLD: return madvise_cold(vma, prev, start, end); case MADV_PAGEOUT: + if (vma->vm_flags & VM_DROPPABLE) + return -EINVAL; return madvise_pageout(vma, prev, start, end); case MADV_FREE: case MADV_DONTNEED: -- 2.45.2