1 files changed, 10 insertions, 31 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index f2d945688025..9b4e7fd0ee66 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -992,9 +992,11 @@ EXPORT_SYMBOL(d_prune_aliases);
 
 /*
  * Lock a dentry from shrink list.
+ * Called under rcu_read_lock() and dentry->d_lock; the former
+ * guarantees that nothing we access will be freed under us.
  * Note that dentry is *not* protected from concurrent dentry_kill(),
- * d_delete(), etc.  It is protected from freeing (by the fact of
- * being on a shrink list), but everything else is fair game.
+ * d_delete(), etc.
+ *
  * Return false if dentry has been disrupted or grabbed, leaving
  * the caller to kick it off-list.  Otherwise, return true and have
  * that dentry's inode and parent both locked.
@@ -1009,7 +1011,6 @@ static bool shrink_lock_dentry(struct dentry *dentry)
 
 	inode = dentry->d_inode;
 	if (inode && unlikely(!spin_trylock(&inode->i_lock))) {
-		rcu_read_lock();	/* to protect inode */
 		spin_unlock(&dentry->d_lock);
 		spin_lock(&inode->i_lock);
 		spin_lock(&dentry->d_lock);
@@ -1018,16 +1019,13 @@ static bool shrink_lock_dentry(struct dentry *dentry)
 		/* changed inode means that somebody had grabbed it */
 		if (unlikely(inode != dentry->d_inode))
 			goto out;
-		rcu_read_unlock();
 	}
 
 	parent = dentry->d_parent;
 	if (IS_ROOT(dentry) || likely(spin_trylock(&parent->d_lock)))
 		return true;
 
-	rcu_read_lock();		/* to protect parent */
 	spin_unlock(&dentry->d_lock);
-	parent = READ_ONCE(dentry->d_parent);
 	spin_lock(&parent->d_lock);
 	if (unlikely(parent != dentry->d_parent)) {
 		spin_unlock(&parent->d_lock);
@@ -1035,15 +1033,12 @@ static bool shrink_lock_dentry(struct dentry *dentry)
 		goto out;
 	}
 	spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-	if (likely(!dentry->d_lockref.count)) {
-		rcu_read_unlock();
+	if (likely(!dentry->d_lockref.count))
 		return true;
-	}
 	spin_unlock(&parent->d_lock);
 out:
 	if (inode)
 		spin_unlock(&inode->i_lock);
-	rcu_read_unlock();
 	return false;
 }
 
@@ -1051,12 +1046,13 @@ static void shrink_dentry_list(struct list_head *list)
 {
 	while (!list_empty(list)) {
 		struct dentry *dentry, *parent;
-		struct inode *inode;
 
 		dentry = list_entry(list->prev, struct dentry, d_lru);
 		spin_lock(&dentry->d_lock);
+		rcu_read_lock();
 		if (!shrink_lock_dentry(dentry)) {
 			bool can_free = false;
+			rcu_read_unlock();
 			d_shrink_del(dentry);
 			if (dentry->d_lockref.count < 0)
 				can_free = dentry->d_flags & DCACHE_MAY_FREE;
@@ -1065,6 +1061,7 @@ static void shrink_dentry_list(struct list_head *list)
 				dentry_free(dentry);
 			continue;
 		}
+		rcu_read_unlock();
 		d_shrink_del(dentry);
 		parent = dentry->d_parent;
 		__dentry_kill(dentry);
@@ -1077,26 +1074,8 @@ static void shrink_dentry_list(struct list_head *list)
 		 * fragmentation.
 		 */
 		dentry = parent;
-		while (dentry && !lockref_put_or_lock(&dentry->d_lockref)) {
-			parent = lock_parent(dentry);
-			if (dentry->d_lockref.count != 1) {
-				dentry->d_lockref.count--;
-				spin_unlock(&dentry->d_lock);
-				if (parent)
-					spin_unlock(&parent->d_lock);
-				break;
-			}
-			inode = dentry->d_inode;	/* can't be NULL */
-			if (unlikely(!spin_trylock(&inode->i_lock))) {
-				spin_unlock(&dentry->d_lock);
-				if (parent)
-					spin_unlock(&parent->d_lock);
-				cpu_relax();
-				continue;
-			}
-			__dentry_kill(dentry);
-			dentry = parent;
-		}
+		while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
+			dentry = dentry_kill(dentry);
 	}
 }