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Sun, 19 Jan 2025 18:02:29 -0800 (PST) MIME-Version: 1.0 References: <20250120013038.6657-1-ioworker0@gmail.com> In-Reply-To: <20250120013038.6657-1-ioworker0@gmail.com> From: Barry Song <21cnbao@gmail.com> Date: Mon, 20 Jan 2025 15:02:18 +1300 X-Gm-Features: AbW1kvalCJl_MJmWr75Bni9ISm3ZQrNQ8k4dS1ekazw5Pwy7aHeC7SFmcoqrn-g Message-ID: Subject: Re: [RFC 1/1] mm/madvise: fail MADV_PAGEOUT on VM_DROPPABLE VMA To: Lance Yang Cc: akpm@linux-foundation.org, 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, Mingzhe Yang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 559E7140009 X-Stat-Signature: gytnewui176n6ybn5dreomxgi86ei6g1 X-Rspam-User: X-HE-Tag: 1737338550-660385 X-HE-Meta: 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 YGvjn9dN 6/MFBej9JY6XmApJrMMXX9wxUkiH7JHOe15p6tzVKDWgvlT5X+L5zszMDkuZgMDjBbm9eDyG8heWLZxcCuEfjpVNYLnokZHbwDJ2VzlEjYx0RuP8bkd8EmffdKPjAKbygNMc9qaFKYzfiisJEDkAJVg0yrxEzhuvNg+4NG13cTDgnww/ZNRfD95QYqDuuYIWo37DYdLCs4bbNZtYO6xT8xIvWGMKOw3ksjuyaVpvrhUSdIfEQO5G/Eo32Ut0PEVL3GIuzj4AEAomQVFPZdTGcpDm05ljcK8xQoKpPQWwpADJegW+qt5Rr+mQN0Kp1sVihSBDuQW/piI4BjLOCHLK3RoCcq5LtYY09QImoz0qgcACLWheAgh3NWuHP3BBqsW2MOmdcr7mtPkLHfIvmsSb1C6XH6jYERS5JjO4zbfvDVOw1U4KHRqksDwnwP6XKvmds7pR6 X-Bogosity: Ham, tests=bogofilter, spamicity=0.422431, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jan 20, 2025 at 2:31=E2=80=AFPM Lance Yang wr= ote: > > 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 I am not convinced this is a correct patch. try_to_unmap_one() will drop the folio. madvise_pageout(vma, prev, start, end) will still go to shrink_folio_list()= and try_to_unmap_one(). > --- > 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_stru= ct *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 > Thanks Barry