From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938577AbcKWPxJ (ORCPT ); Wed, 23 Nov 2016 10:53:09 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:34030 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935769AbcKWPxE (ORCPT ); Wed, 23 Nov 2016 10:53:04 -0500 Date: Wed, 23 Nov 2016 15:53:01 +0000 From: Al Viro To: Alexei Starovoitov Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Daniel Borkmann , Martin KaFai Lau Subject: Re: sendfile from 9p fs into af_alg Message-ID: <20161123155301.GP1555@ZenIV.linux.org.uk> References: <20161123035827.GA43786@ast-mbp.thefacebook.com> <20161123044625.GL1555@ZenIV.linux.org.uk> <20161123045558.GA43893@ast-mbp.thefacebook.com> <20161123061628.GN1555@ZenIV.linux.org.uk> <20161123085809.GA46992@ast-mbp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161123085809.GA46992@ast-mbp.thefacebook.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 23, 2016 at 12:58:11AM -0800, Alexei Starovoitov wrote: > if I read it correctly 9p actually responded with 8192 bytes of requests... > whereas the file size was 9624. > For large file sizes (in megabytes) the difference between what > sendfile is reporting and actual file size can be 3x. > In the small file case (like above dump) it looks rounded to page size for some reason. OK, I think I see one bug in there; could you check if this gets it back to normal? diff --git a/fs/splice.c b/fs/splice.c index dcaf185..5a7750b 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -408,7 +408,8 @@ static ssize_t default_file_splice_read(struct file *in, loff_t *ppos, if (res <= 0) return -ENOMEM; - nr_pages = res / PAGE_SIZE; + BUG_ON(dummy); + nr_pages = DIV_ROUND_UP(res, PAGE_SIZE); vec = __vec; if (nr_pages > PIPE_DEF_BUFFERS) {