Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754451AbXFLDJT (ORCPT ); Mon, 11 Jun 2007 23:09:19 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752113AbXFLDJJ (ORCPT ); Mon, 11 Jun 2007 23:09:09 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:41365 "HELO ustc.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1751015AbXFLDJI (ORCPT ); Mon, 11 Jun 2007 23:09:08 -0400 Message-ID: <381617742.09898@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20070612030905.812075843@mail.ustc.edu.cn> References: <20070612030450.590659600@mail.ustc.edu.cn> User-Agent: quilt/0.45-1 Date: Tue, 12 Jun 2007 11:00:34 +0800 From: Fengguang Wu To: Andrew Morton Cc: Jens Axboe , linux-kernel@vger.kernel.org Subject: [PATCH 2/2] readahead: pass real splice size Content-Disposition: inline; filename=readahead-fix-splice-size.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2269 Lines: 63 Pass real splice size to page_cache_readahead_ondemand(). The splice code works in chunks of 16 pages internally. The readahead code should be told of the overall splice size, instead of the internal chunk size. Otherwize bad things may happen. Imagine some 17-page random splice reads. The code before this patch will result in two readahead calls: readahead(16); readahead(1); That leads to one 16-page I/O and one 32-page I/O: one extra I/O and 31 readahead miss pages. Signed-off-by: Fengguang Wu --- fs/splice.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) --- linux-2.6.22-rc3-mm1.orig/fs/splice.c +++ linux-2.6.22-rc3-mm1/fs/splice.c @@ -267,7 +267,7 @@ __generic_file_splice_read(struct file * unsigned int flags) { struct address_space *mapping = in->f_mapping; - unsigned int loff, nr_pages; + unsigned int loff, nr_pages, req_pages; struct page *pages[PIPE_BUFFERS]; struct partial_page partial[PIPE_BUFFERS]; struct page *page; @@ -284,10 +284,8 @@ __generic_file_splice_read(struct file * index = *ppos >> PAGE_CACHE_SHIFT; loff = *ppos & ~PAGE_CACHE_MASK; - nr_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; - - if (nr_pages > PIPE_BUFFERS) - nr_pages = PIPE_BUFFERS; + req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT; + nr_pages = min(req_pages, (unsigned)PIPE_BUFFERS); /* * Now fill in the holes: @@ -307,7 +305,7 @@ __generic_file_splice_read(struct file * */ if (spd.nr_pages < nr_pages) page_cache_readahead_ondemand(mapping, &in->f_ra, in, - NULL, index, nr_pages - spd.nr_pages); + NULL, index, req_pages - spd.nr_pages); while (spd.nr_pages < nr_pages) { /* @@ -363,7 +361,7 @@ __generic_file_splice_read(struct file * if (PageReadahead(page)) page_cache_readahead_ondemand(mapping, &in->f_ra, in, - page, index, nr_pages - page_nr); + page, index, req_pages - page_nr); /* * If the page isn't uptodate, we may need to start io on it -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/