From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758392Ab0KPOYz (ORCPT ); Tue, 16 Nov 2010 09:24:55 -0500 Received: from ipmail05.adl6.internode.on.net ([150.101.137.143]:32788 "EHLO ipmail05.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758625Ab0KPOYH (ORCPT ); Tue, 16 Nov 2010 09:24:07 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AogKAKMh4kx5Ldur/2dsb2JhbACUX4ECjH1yvmaFSwSKWIUQ Message-Id: <20101116142030.809122063@kernel.dk> User-Agent: quilt/0.48-1 Date: Wed, 17 Nov 2010 01:09:27 +1100 From: Nick Piggin To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org Subject: [patch 27/28] fs: use RCU in shrink_dentry_list to reduce lock nesting References: <20101116140900.039761100@kernel.dk> Content-Disposition: inline; filename=dcache-lru-scanning-rcu.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Nick Piggin --- fs/dcache.c | 38 +++++++++++++++++++++----------------- 1 file changed, 21 insertions(+), 17 deletions(-) Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c 2010-11-17 00:52:38.000000000 +1100 +++ linux-2.6/fs/dcache.c 2010-11-17 01:05:37.000000000 +1100 @@ -580,16 +580,16 @@ static void shrink_dentry_list(struct li { struct dentry *dentry; + rcu_read_lock(); while (!list_empty(list)) { struct dentry *parent; dentry = list_entry(list->prev, struct dentry, d_lru); - if (!spin_trylock(&dentry->d_lock)) { -relock1: - spin_unlock(&dcache_lru_lock); - cpu_relax(); - spin_lock(&dcache_lru_lock); + /* Don't need RCU dereference because we recheck under lock */ + spin_lock(&dentry->d_lock); + if (dentry != list_entry(list->prev, struct dentry, d_lru)) { + spin_unlock(&dentry->d_lock); continue; } @@ -599,14 +599,16 @@ static void shrink_dentry_list(struct li * it - just keep it off the LRU list. */ if (dentry->d_count) { - __dentry_lru_del(dentry); + dentry_lru_del(dentry); spin_unlock(&dentry->d_lock); continue; } + if (!spin_trylock(&dcache_inode_lock)) { -relock2: +relock: spin_unlock(&dentry->d_lock); - goto relock1; + cpu_relax(); + continue; } if (IS_ROOT(dentry)) parent = NULL; @@ -614,15 +616,15 @@ static void shrink_dentry_list(struct li parent = dentry->d_parent; if (parent && !spin_trylock(&parent->d_lock)) { spin_unlock(&dcache_inode_lock); - goto relock2; + goto relock; } - __dentry_lru_del(dentry); - spin_unlock(&dcache_lru_lock); + dentry_lru_del(dentry); + rcu_read_unlock(); prune_one_dentry(dentry, parent); - /* dcache_inode_lock and dentry->d_lock dropped */ - spin_lock(&dcache_lru_lock); + rcu_read_lock(); } + rcu_read_unlock(); } /** @@ -671,13 +673,13 @@ static void __shrink_dcache_sb(struct su break; } } - - *count = cnt; - shrink_dentry_list(&tmp); - if (!list_empty(&referenced)) list_splice(&referenced, &sb->s_dentry_lru); spin_unlock(&dcache_lru_lock); + + shrink_dentry_list(&tmp); + + *count = cnt; } /** @@ -769,7 +771,9 @@ void shrink_dcache_sb(struct super_block spin_lock(&dcache_lru_lock); while (!list_empty(&sb->s_dentry_lru)) { list_splice_init(&sb->s_dentry_lru, &tmp); + spin_unlock(&dcache_lru_lock); shrink_dentry_list(&tmp); + spin_lock(&dcache_lru_lock); } spin_unlock(&dcache_lru_lock); }