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b=rleA7Q5F12Eow+XD+tZnHSctqeL3D9Ff1H88myZ+EhzFCsEUxCY1TeHKrN5vUd1on lSidBKoUoe4z4cE6FYjOLQmDIw47e7Uwlf/RIUdizj0rh+vJA1an0TWKtaLPnWW11+ SYU2UcATvkP8dItxb9ScLadbutkefcyaAVQhk+s93WT2rjqJOk2LyR1FxHXHuwRt8s G66+rqKRLf6H32b5HiQ72uCtPNZyyVuwsAvYzjdDhgQFiLub2wBnweSp0v9TX8w9sa mtVXpahw9aqEGyFqC2Rw32mb70iI0hqLV9Ew9maNMOjASYCmDvYEg8reM/oERKDUjs 97dsgB9d8q0RQ== Date: Wed, 8 Apr 2026 18:08:55 +0000 From: Jaegeuk Kim To: "David Hildenbrand (Arm)" Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] f2fs: do not support mmap write for large folio Message-ID: References: <20260406154940.2407853-1-jaegeuk@kernel.org> <2aee26dd-703b-47c4-9210-f70ffa6faf09@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2aee26dd-703b-47c4-9210-f70ffa6faf09@kernel.org> X-Rspamd-Server: rspam12 X-Stat-Signature: x9637kcetw6biosqshynna1qcxik1fj7 X-Rspamd-Queue-Id: C60B5C0017 X-Rspam-User: X-HE-Tag: 1775671737-617675 X-HE-Meta: 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 nCY+u2sO jTIQ0o/Gz6Zf5LzmZkm9kKnEh9e0l5qfF30pqhK56CLmdKOkVy0oeZENiTWiQNIe6MV9NNDJ9e2E3psFC36D/HSmJ707qMD9dx6MUtsFHCxGyJjDTPUhTefqAnF6Qsqx6Us4npPeqi4Y8+/Jkn5zrL4H4PMrByNEJFjRxYmf5+T14axP5swA/mLJ2G65AjdOxQ02Sz7djN05+efl4COqpDebjN/YluWBU/fv2rPvAG5RBMGHrrDlMrf6cQbdwx4b5ikyRcAHGlno/tQI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04/08, David Hildenbrand (Arm) wrote: > On 4/8/26 07:03, Christoph Hellwig wrote: > > On Tue, Apr 07, 2026 at 10:58:11PM +0000, Jaegeuk Kim wrote: > >> On 04/06, Christoph Hellwig wrote: > >>> > >>> Why? And how is this not breaking applications? > >> > >> Since we only support the large folio on the read case. > > > > In general spelling such basic out in the commit log, and even comments > > is really helpful. I'm curious how this works, though - by the time > > you read a large folio you don't know if it will ever be written to. > > Why are only large folios supported for read? > > Where is that allocation logic and how can that path even be triggered? > > Also, usually we check for large folios by testing the actual folio, not > whether the mapping supports them? https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v7.0-rc7&id=05e65c14ea59a401cec4284e9d612f9d5dc1b3f8 Currently I think it's simple to check the mapping in our case. > > -- > Cheers, > > David