From: Robin Dong Subject: [PATCH v3] ext4: avoid wasted extent cache lookup if !PUNCH_OUT_EXT Date: Wed, 29 Jun 2011 08:57:51 +0800 Message-ID: <1309309071-2244-1-git-send-email-sanbai@taobao.com> Cc: Robin Dong To: linux-ext4@vger.kernel.org Return-path: Received: from mail-iw0-f174.google.com ([209.85.214.174]:47994 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750821Ab1F2A6B (ORCPT ); Tue, 28 Jun 2011 20:58:01 -0400 Received: by iwn6 with SMTP id 6so619727iwn.19 for ; Tue, 28 Jun 2011 17:58:00 -0700 (PDT) Sender: linux-ext4-owner@vger.kernel.org List-ID: This patch avoids an extraneous lookup of the extent cache in ext4_ext_map_blocks() when the flag EXT4_GET_BLOCKS_PUNCH_OUT_EXT is absent. The existing logic was performing the lookup but not making use of the result. The patch simply reverses the order of evaluation in the condition. Since ext4_ext_in_cache() does not initialize newex on misses, bypassing its invocation does not introduce any new issue in this regard. Signed-off-by: Robin Dong Reviewed-by: Lukas Czerner Reviewed-by: Eric Gouriou --- fs/ext4/extents.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index eb63c7b..fed2633 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -3358,8 +3358,8 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode, trace_ext4_ext_map_blocks_enter(inode, map->m_lblk, map->m_len, flags); /* check in cache */ - if (ext4_ext_in_cache(inode, map->m_lblk, &newex) && - ((flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) == 0)) { + if (!(flags & EXT4_GET_BLOCKS_PUNCH_OUT_EXT) && + ext4_ext_in_cache(inode, map->m_lblk, &newex)) { if (!newex.ee_start_lo && !newex.ee_start_hi) { if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) { /* -- 1.7.1