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Howlett" , Vlastimil Babka , Jann Horn , Matthew Wilcox , Jan Kara Subject: Re: [RFC] madvise: best-effort deferred writeback for shared file mappings Message-ID: References: <85aff663-2131-47da-ac04-8f0799a49b91@kernel.org> <1ce9cf3a-15dc-4815-ba29-2e22b05206fb@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: CDA774000B X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: kny47a9bdx1hm6mthiuwqcje7td41cdk X-HE-Tag: 1790782999-149639 X-HE-Meta: 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 ofDavh6a mLNeQ/GPFdS1EgtJAvTEv9QkMbfHatmlnqECX4qHe5WLGV7GKGTN01sbs9uzS+NFsqQWMz4VKyaI4Sc0jFnWXy3a2m8Hi4iJmuCaoczn7xdZVWLWIP9YFtO51k7qA3Fd2cCFkCQTSnuVLgVwmaXkx2Ktvc534AYZHt7r9Ki+C81caqJCXhkWaIxOlKh9d8NWNCKbAGmxa5Ep7OhEIa1A1Zz1oVCd0laDm/q+xL6SBnXRVOyGh8G/r98Wx48mxvU55LMOVlt9O58Gh/91cqZPitUkIx9UOgQFakUuspIx1ALvYdjo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Sep 30, 2026 at 11:29:09PM +0800, 天狼 wrote: > Hi David, Lorenzo, ... > Per-file deferred writeback would require minimal kernel changes and pose > a very low risk, while offering enormous benefits. I'm afraid the opposite is true. The proposed expiry hint does nothing as soon as you hit the dirty background threshold and in any case violates kernel writeback as explained. And nothing you've proposed here is upstreamable. A locked down simple process handing out memfds (as explained in detail in other mail) or a named tmpfs file survives process crash perfectly fine and is the correct shape of the solution. This is what you should pursue. -- Cheers, Lorenzo