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Fri, 25 Oct 2024 08:33:00 -0700 (PDT) MIME-Version: 1.0 References: <20241014182228.1941246-1-joannelkoong@gmail.com> <20241014182228.1941246-3-joannelkoong@gmail.com> <3e4ff496-f2ed-42ef-9f1a-405f32aa1c8c@linux.alibaba.com> In-Reply-To: <3e4ff496-f2ed-42ef-9f1a-405f32aa1c8c@linux.alibaba.com> From: Miklos Szeredi Date: Fri, 25 Oct 2024 17:32:49 +0200 Message-ID: Subject: Re: [PATCH v2 2/2] fuse: remove tmp folio for writebacks and internal rb tree To: Jingbo Xu Cc: Joanne Koong , Shakeel Butt , linux-fsdevel@vger.kernel.org, josef@toxicpanda.com, bernd.schubert@fastmail.fm, hannes@cmpxchg.org, linux-mm@kvack.org, kernel-team@meta.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 93FA5C0023 X-Stat-Signature: aiuf98wm1yoj5cgjfnqr8szg6frskrbc X-Rspam-User: X-HE-Tag: 1729870372-271418 X-HE-Meta: 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 yoOuxMA5 xwXKWQWe8gR3p+m1QQN6cB8tXEbhwWwWwCYgzOJYxvb/Sryo8GFXgvJN/AlLXU6u5cft+i4J7Y22J0i7VdzGPKdOQyipqWzc1alr6S1g3+h/R7lD+v4449noTQTWfeHZ6vuqS1zP+aBQ7rn5fd5y3PywijLKbeFojcPevPfvHrxMl7p7UKwvadylXmV3KyWirpZdsNrwPA919bHcTI8y/D5jYCYfTKzT/xibG2NSvv9LyfOIO3r+run53VCOOCFs/ZRwlWWQKN2co1hw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000088, 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 Fri, 25 Oct 2024 at 03:38, Jingbo Xu wrote: > Actually as for FUSE, IIUC the writeback is not guaranteed to be > completed when sync(2) returns since the temp page mechanism. When > sync(2) returns, PG_writeback is indeed cleared for all original pages > (in the address_space), while the real writeback work (initiated from > temp page) may be still in progress. Correct, this is the current behavior of fuse. I'm not against changing this for the privileged server case. I.e. a server running with certain privileges (e.g. CAP_SYS_ADMIN in the global namespace) then it should be able to opt in to waiting sync(2) behavior. > I think this is also what Miklos means in: > https://lore.kernel.org/all/CAJfpegsJKD4YT5R5qfXXE=hyqKvhpTRbD4m1wsYNbGB6k4rC2A@mail.gmail.com/ > > Though we need special handling for AS_NO_WRITEBACK_RECLAIM marked pages > in sync(2) codepath similar to what we have done for the direct reclaim > in patch 1. I'd love to get rid of the tmp page thing completely if the same guarantees can be implemented in the mm. Thanks, Miklos