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Fri, 17 Feb 2023 01:18:18 -0800 (PST) X-Google-Smtp-Source: AK7set+lIxm58KEM1AennY2XsrLAcbikGNILzL6qgYViYa+ApoQ4BacvYccgWrTzqtVkNDIoILRdGOjWEC3MmtgRAVo= X-Received: by 2002:a05:6102:3b0b:b0:414:13c7:f583 with SMTP id x11-20020a0561023b0b00b0041413c7f583mr714101vsu.78.1676625497977; Fri, 17 Feb 2023 01:18:17 -0800 (PST) MIME-Version: 1.0 References: <20230214171330.2722188-1-dhowells@redhat.com> <20230214171330.2722188-9-dhowells@redhat.com> In-Reply-To: From: Ming Lei Date: Fri, 17 Feb 2023 17:18:06 +0800 Message-ID: Subject: Re: [PATCH v14 08/17] splice: Do splice read from a file without using ITER_PIPE To: David Howells Cc: Jens Axboe , Al Viro , Christoph Hellwig , Matthew Wilcox , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Hellwig , John Hubbard X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 2595B12000A X-Stat-Signature: 4cok13oup3rhnbomu1youuzpypo7irh6 X-HE-Tag: 1676625501-961614 X-HE-Meta: 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 NjuuWsy+ 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 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: On Fri, Feb 17, 2023 at 4:22 PM Ming Lei wrote: > > On Tue, Feb 14, 2023 at 05:13:21PM +0000, David Howells wrote: > > Make generic_file_splice_read() use filemap_splice_read() and > > direct_splice_read() rather than using an ITER_PIPE and call_read_iter(). > > > > With this, ITER_PIPE is no longer used. > > > > Signed-off-by: David Howells > > cc: Jens Axboe > > cc: Christoph Hellwig > > cc: Al Viro > > cc: David Hildenbrand > > cc: John Hubbard > > cc: linux-mm@kvack.org > > cc: linux-block@vger.kernel.org > > cc: linux-fsdevel@vger.kernel.org > > --- > > > > Notes: > > ver #14) > > - Split out filemap_splice_read() into a separate patch. > > > > fs/splice.c | 30 +++++++----------------------- > > 1 file changed, 7 insertions(+), 23 deletions(-) > > > > diff --git a/fs/splice.c b/fs/splice.c > > index 4c6332854b63..a93478338cec 100644 > > --- a/fs/splice.c > > +++ b/fs/splice.c > > @@ -391,29 +391,13 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, > > struct pipe_inode_info *pipe, size_t len, > > unsigned int flags) > > { > > - struct iov_iter to; > > - struct kiocb kiocb; > > - int ret; > > - > > - iov_iter_pipe(&to, ITER_DEST, pipe, len); > > - init_sync_kiocb(&kiocb, in); > > - kiocb.ki_pos = *ppos; > > - ret = call_read_iter(in, &kiocb, &to); > > - if (ret > 0) { > > - *ppos = kiocb.ki_pos; > > - file_accessed(in); > > - } else if (ret < 0) { > > - /* free what was emitted */ > > - pipe_discard_from(pipe, to.start_head); > > - /* > > - * callers of ->splice_read() expect -EAGAIN on > > - * "can't put anything in there", rather than -EFAULT. > > - */ > > - if (ret == -EFAULT) > > - ret = -EAGAIN; > > - } > > - > > - return ret; > > + if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes)) > > + return 0; > > + if (unlikely(!len)) > > + return 0; > > + if (in->f_flags & O_DIRECT) > > + return direct_splice_read(in, ppos, pipe, len, flags); > > Hello David, > > I have one question, for dio, pages need to map to userspace > memory, but direct_splice_read() just allocates pages and not > see when the user mapping is setup, can you give one hint? oops, it is ->splice_read, not ->read_iter, and pipe buffer isn't user-backed, sorry for the noise. Thanks, Ming