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Mon, 17 Nov 2025 09:53:04 -0800 (PST) MIME-Version: 1.0 References: <955478b5170715c895d1ef3b7f68e0cd77f76868.1763399675.git.lorenzo.stoakes@oracle.com> In-Reply-To: <955478b5170715c895d1ef3b7f68e0cd77f76868.1763399675.git.lorenzo.stoakes@oracle.com> From: Andrei Vagin Date: Mon, 17 Nov 2025 09:52:52 -0800 X-Gm-Features: AWmQ_bklapVnnz45ORmvR4yt1OrQiai2bKIStrRIIFocxcpx30j3kcA5143cdVg Message-ID: Subject: Re: [PATCH v2 1/2] mm: propagate VM_SOFTDIRTY on merge To: Lorenzo Stoakes Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B519F180014 X-Stat-Signature: t9pe9rgmcehgwbjc9y1u4sj3kg6e3buf X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1763401985-182122 X-HE-Meta: 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 H5yayfon 9+//k41V1SddH1xsUA5H+p2/80842cEomybFZ8NK064NBUsJJMd88pVppGhdsxDzBUWRx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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, Nov 17, 2025 at 9:40=E2=80=AFAM Lorenzo Stoakes wrote: > > Currently we set VM_SOFTDIRTY when a new mapping is set up (whether by > establishing a new VMA, or via merge) as implemented in __mmap_complete() > and do_brk_flags(). > > However, when performing a merge of existing mappings such as when > performing mprotect(), we may lose the VM_SOFTDIRTY flag. > > This is because currently we simply ignore VM_SOFTDIRTY for the purposes > of merge, so one VMA may possess the flag and another not, and whichever > happens to be the target VMA will be the one upon which the merge is > performed which may or may not have VM_SOFTDIRTY set. > > Now we have the concept of 'sticky' VMA flags, let's make VM_SOFTDIRTY on= e > which solves this issue. > > Additionally update VMA userland tests to propagate changes. > > Signed-off-by: Lorenzo Stoakes > Suggested-by: Vlastimil Babka > Acked-by: David Hildenbrand (Red Hat) > Reviewed-by: Pedro Falcato Acked-by: Andrey Vagin Thanks, Andrei