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Fri, 17 Feb 2023 03:22:30 -0500 X-MC-Unique: mKHUGlstPr2G68_UGsxnAw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 112C885A5A3; Fri, 17 Feb 2023 08:22:30 +0000 (UTC) Received: from T590 (ovpn-8-26.pek2.redhat.com [10.72.8.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 180E6492C3E; Fri, 17 Feb 2023 08:22:19 +0000 (UTC) Date: Fri, 17 Feb 2023 16:22:14 +0800 From: Ming Lei 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 , ming.lei@redhat.com Subject: Re: [PATCH v14 08/17] splice: Do splice read from a file without using ITER_PIPE Message-ID: References: <20230214171330.2722188-1-dhowells@redhat.com> <20230214171330.2722188-9-dhowells@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230214171330.2722188-9-dhowells@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 X-Rspam-User: X-Rspamd-Queue-Id: 79F644000C X-Rspamd-Server: rspam01 X-Stat-Signature: ru1g86zym8ih985degh9bsz3bhxxdfta X-HE-Tag: 1676622157-656759 X-HE-Meta: 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 VNURaz6B 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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 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? Thanks, Ming