From: Nick Piggin <npiggin@kernel.dk>
Date: Fri, 7 Jan 2011 06:49:42 +0000 (+1100)
Subject: fs: dcache reduce dcache_inode_lock
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=357f8e658bba8a085c4a5d4331e30894be8096b8;p=openwrt%2Fstaging%2Fblogic.git

fs: dcache reduce dcache_inode_lock

dcache_inode_lock can be avoided in d_delete() and d_materialise_unique()
in cases where it is not required.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index ccdc5c2512df..01f016799fd4 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1828,10 +1828,15 @@ void d_delete(struct dentry * dentry)
 	/*
 	 * Are we the only user?
 	 */
-	spin_lock(&dcache_inode_lock);
+again:
 	spin_lock(&dentry->d_lock);
 	isdir = S_ISDIR(dentry->d_inode->i_mode);
 	if (dentry->d_count == 1) {
+		if (!spin_trylock(&dcache_inode_lock)) {
+			spin_unlock(&dentry->d_lock);
+			cpu_relax();
+			goto again;
+		}
 		dentry->d_flags &= ~DCACHE_CANT_MOUNT;
 		dentry_iput(dentry);
 		fsnotify_nameremove(dentry, isdir);
@@ -1842,7 +1847,6 @@ void d_delete(struct dentry * dentry)
 		__d_drop(dentry);
 
 	spin_unlock(&dentry->d_lock);
-	spin_unlock(&dcache_inode_lock);
 
 	fsnotify_nameremove(dentry, isdir);
 }
@@ -2164,14 +2168,15 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 
 	BUG_ON(!d_unhashed(dentry));
 
-	spin_lock(&dcache_inode_lock);
-
 	if (!inode) {
 		actual = dentry;
 		__d_instantiate(dentry, NULL);
-		goto found_lock;
+		d_rehash(actual);
+		goto out_nolock;
 	}
 
+	spin_lock(&dcache_inode_lock);
+
 	if (S_ISDIR(inode->i_mode)) {
 		struct dentry *alias;
 
@@ -2198,10 +2203,9 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 	actual = __d_instantiate_unique(dentry, inode);
 	if (!actual)
 		actual = dentry;
-	else if (unlikely(!d_unhashed(actual)))
-		goto shouldnt_be_hashed;
+	else
+		BUG_ON(!d_unhashed(actual));
 
-found_lock:
 	spin_lock(&actual->d_lock);
 found:
 	spin_lock(&dcache_hash_lock);
@@ -2217,10 +2221,6 @@ out_nolock:
 
 	iput(inode);
 	return actual;
-
-shouldnt_be_hashed:
-	spin_unlock(&dcache_inode_lock);
-	BUG();
 }
 EXPORT_SYMBOL_GPL(d_materialise_unique);