From: Miklos Szeredi <mszeredi@suse.cz>
Date: Fri, 2 May 2014 19:38:39 +0000 (-0400)
Subject: dcache: don't need rcu in shrink_dentry_list()
X-Git-Tag: v3.12.32~127
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=72b7f65091199b7ae38ad658c5ce8246f1496976;p=thirdparty%2Fkernel%2Fstable.git

dcache: don't need rcu in shrink_dentry_list()

commit 60942f2f235ce7b817166cdf355eed729094834d upstream.

Since now the shrink list is private and nobody can free the dentry while
it is on the shrink list, we can remove RCU protection from this.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index b688034caa4dd..4b2cb57d6541c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -818,23 +818,9 @@ static void shrink_dentry_list(struct list_head *list)
 {
 	struct dentry *dentry, *parent;
 
-	rcu_read_lock();
-	for (;;) {
-		dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
-		if (&dentry->d_lru == list)
-			break; /* empty */
-
-		/*
-		 * Get the dentry lock, and re-verify that the dentry is
-		 * this on the shrinking list. If it is, we know that
-		 * DCACHE_SHRINK_LIST and DCACHE_LRU_LIST are set.
-		 */
+	while (!list_empty(list)) {
+		dentry = list_entry(list->prev, struct dentry, d_lru);
 		spin_lock(&dentry->d_lock);
-		if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
-			spin_unlock(&dentry->d_lock);
-			continue;
-		}
-
 		/*
 		 * The dispose list is isolated and dentries are not accounted
 		 * to the LRU here, so we can simply remove it from the list
@@ -850,23 +836,20 @@ static void shrink_dentry_list(struct list_head *list)
 			spin_unlock(&dentry->d_lock);
 			continue;
 		}
-		rcu_read_unlock();
 
 		parent = dentry_kill(dentry, 0);
 		/*
 		 * If dentry_kill returns NULL, we have nothing more to do.
 		 */
-		if (!parent) {
-			rcu_read_lock();
+		if (!parent)
 			continue;
-		}
+
 		if (unlikely(parent == dentry)) {
 			/*
 			 * trylocks have failed and d_lock has been held the
 			 * whole time, so it could not have been added to any
 			 * other lists. Just add it back to the shrink list.
 			 */
-			rcu_read_lock();
 			d_shrink_add(dentry, list);
 			spin_unlock(&dentry->d_lock);
 			continue;
@@ -880,9 +863,7 @@ static void shrink_dentry_list(struct list_head *list)
 		dentry = parent;
 		while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
 			dentry = dentry_kill(dentry, 1);
-		rcu_read_lock();
 	}
-	rcu_read_unlock();
 }
 
 static enum lru_status