Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754486Ab0FXDQl (ORCPT ); Wed, 23 Jun 2010 23:16:41 -0400 Received: from cantor2.suse.de ([195.135.220.15]:36010 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142Ab0FXDPr (ORCPT ); Wed, 23 Jun 2010 23:15:47 -0400 Message-Id: <20100624030729.395195069@suse.de> User-Agent: quilt/0.48-4.4 Date: Thu, 24 Jun 2010 13:02:36 +1000 From: npiggin@suse.de To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: John Stultz , Frank Mayhar Subject: [patch 24/52] fs: dcache reduce d_parent locking References: <20100624030212.676457061@suse.de> Content-Disposition: inline; filename=fs-dget_parent-opt.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2070 Lines: 78 Use RCU property of dcache to simplify locking in some places where we take d_parent and d_lock. Comment: don't need rcu_deref because we take the spinlock and recheck it. Signed-off-by: Nick Piggin -- Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c +++ linux-2.6/fs/dcache.c @@ -311,23 +311,18 @@ struct dentry *dget_parent(struct dentry struct dentry *ret; repeat: - spin_lock(&dentry->d_lock); + rcu_read_lock(); ret = dentry->d_parent; - if (!ret) - goto out; - if (dentry == ret) { - ret->d_count++; - goto out; - } - if (!spin_trylock(&ret->d_lock)) { - spin_unlock(&dentry->d_lock); + spin_lock(&ret->d_lock); + if (unlikely(ret != dentry->d_parent)) { + spin_unlock(&ret->d_lock); + rcu_read_unlock(); goto repeat; } + rcu_read_unlock(); BUG_ON(!ret->d_count); ret->d_count++; spin_unlock(&ret->d_lock); -out: - spin_unlock(&dentry->d_lock); return ret; } EXPORT_SYMBOL(dget_parent); @@ -601,14 +596,22 @@ static void prune_one_dentry(struct dent if (inode) spin_lock(&inode->i_lock); again: - spin_lock(&dentry->d_lock); - if (dentry->d_parent && dentry != dentry->d_parent) { - if (!spin_trylock(&dentry->d_parent->d_lock)) { - spin_unlock(&dentry->d_lock); + rcu_read_lock(); + parent = dentry->d_parent; + if (parent) { + spin_lock(&parent->d_lock); + if (unlikely(parent != dentry->d_parent)) { + spin_unlock(&parent->d_lock); + rcu_read_unlock(); goto again; } - parent = dentry->d_parent; - } + if (parent != dentry) + spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); + else + parent = NULL; + } else + spin_lock(&dentry->d_lock); + rcu_read_unlock(); dentry->d_count--; if (dentry->d_count) { if (parent) -- 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/