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bh=NQQfCWFU8lTMyB4kZpp1AQfeK0U34PKN96OHaEuI3NM=; b=w22PAIkr9oIIXybbe3DbBV7xf0A+BT4Mu/TKdghh9H9Xrhbbc8gHzZlXoyfApOMVmx8+MtlhCUnQOKPAO9Y/hTMUvetKWYO+SwW5ByVGi17kp2HPvbbCeJ51b1wGIPtF+WJgGvwA6SvE0g8Vi4WLxwV86v6JBbLN1FW4dATGAhE= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R891e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033032089153;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0X9JeZM._1787232889; Received: from 30.42.155.165(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0X9JeZM._1787232889 cluster:ay36) by smtp.aliyun-inc.com; Thu, 20 Aug 2026 21:34:50 +0800 Message-ID: <76ee52de-1dcb-44da-b2cf-329864adca07@linux.alibaba.com> Date: Thu, 20 Aug 2026 21:34:49 +0800 X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] erofs: use the shared page cache for splice in inode_share mode To: Zhan Xusheng , Gao Xiang , Chao Yu Cc: Zhan Xusheng , linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org References: <20260820064441.1083470-1-zhanxusheng@xiaomi.com> <3d735f18-2d26-4b4c-be68-b000742e9826@linux.alibaba.com> <20260820123705.1748738-1-zhanxusheng@xiaomi.com> Content-Language: en-US From: Jingbo Xu In-Reply-To: <20260820123705.1748738-1-zhanxusheng@xiaomi.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/20/26 8:37 PM, Zhan Xusheng wrote: > On Thu, 20 Aug 2026 17:53:20 +0800, Jingbo Xu wrote: >> Please refer to backing_file_splice_read() called from >> ovl_splice_read(), file_accessed() needs to be called on the original >> file (just as what .read_iter() i.e. filemap_read() does), and the input >> @ppos needs to be updated accordingly. > > Taking the file_accessed() one, thanks. filemap_splice_read() calls it at > mm/filemap.c:3155 on whatever file it was handed, so on the backing file, > whereas backing_file_splice_read() ends in ctx->accessed(iocb->ki_filp), > which for ovl_splice_read() is the original. v2 adds file_accessed(in). > > @ppos looks already handled to me. filemap_splice_read() takes a loff_t * > and advances it itself, at mm/filemap.c:3144; its internal kiocb is seeded > from *ppos at 3083 and 3098, not the other way round. ovl_splice_read() > has to copy iocb.ki_pos back because backing_file_splice_read() takes a > struct kiocb and hands &iocb->ki_pos to vfs_splice_read(). Say if I have > that wrong. Make sense. > > One you may want for read_iter too: it clones the kiocb onto the backing > file, so filemap_read() marks that one accessed rather than the user's > file, which is the shape splice_read had. Neither is observable today, > since erofs_fc_fill_super() sets SB_RDONLY | SB_NOATIME and the backing > file is opened O_NOATIME, so both reach a no-op. That is why I left > read_iter alone here. Okay, it seems that file_accessed() shall also be added to erofs_ishare_file_read_iter()? -- Thanks, Jingbo