Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262380AbVCBSLa (ORCPT ); Wed, 2 Mar 2005 13:11:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262398AbVCBSGu (ORCPT ); Wed, 2 Mar 2005 13:06:50 -0500 Received: from mail.tv-sign.ru ([213.234.233.51]:59042 "EHLO several.ru") by vger.kernel.org with ESMTP id S262394AbVCBSDa (ORCPT ); Wed, 2 Mar 2005 13:03:30 -0500 Message-ID: <42260F2C.FCAA1915@tv-sign.ru> Date: Wed, 02 Mar 2005 22:08:28 +0300 From: Oleg Nesterov X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.20 i686) X-Accept-Language: en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Cc: Ram Pai , Steven Pratt , Andrew Morton Subject: [PATCH 1/2] readahead: simplify ra->size testing Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2180 Lines: 57 On top of "readahead: cleanup blockable_page_cache_readahead()", see http://marc.theaimsgroup.com/?l=linux-kernel&m=110927049500942 Currently page_cache_readahead() treats ra->size == 0 (first read) and ra->size == -1 (ra_off was called) separately, but does exactly the same in both cases. With this patch we may assume that the reading starts in 'ra_off()' state, so we don't need to consider the first read as a special case. Signed-off-by: Oleg Nesterov --- 2.6.11/mm/readahead.c~ 2005-02-04 21:33:40.000000000 +0300 +++ 2.6.11/mm/readahead.c 2005-02-04 21:33:57.000000000 +0300 @@ -55,7 +55,7 @@ static inline void ra_off(struct file_ra { ra->start = 0; ra->flags = 0; - ra->size = -1; + ra->size = 0; ra->ahead_start = 0; ra->ahead_size = 0; return; @@ -452,7 +452,7 @@ page_cache_readahead(struct address_spac * perturbing the readahead window expansion logic. * If size is zero, there is no read ahead window so we need one */ - if (offset == ra->prev_page && req_size == 1 && ra->size != 0) + if (offset == ra->prev_page && req_size == 1) goto out; ra->prev_page = offset; @@ -471,9 +471,7 @@ page_cache_readahead(struct address_spac * at start of file, and grow the window fast. Or detect first * sequential access */ - if ((ra->size == 0 && offset == 0) /* first io and start of file */ - || (ra->size == -1 && sequential)) { - /* First sequential */ + if (sequential && ra->size == 0) { ra->size = get_init_ra_size(newsize, max); ra->start = offset; if (!blockable_page_cache_readahead(mapping, filp, offset, @@ -499,7 +497,7 @@ page_cache_readahead(struct address_spac * partial page reads and first access were handled above, * so this must be the next page otherwise it is random */ - if (!sequential || (ra->size == 0)) { + if (!sequential) { ra_off(ra); blockable_page_cache_readahead(mapping, filp, offset, newsize, ra, 1); - 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/