1 files changed, 36 insertions, 47 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index be18598c7fd7..a88948b8bd17 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -301,6 +301,27 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
 	return parent;
 }
 
+/*
+ * Unhash a dentry without inserting an RCU walk barrier or checking that
+ * dentry->d_lock is locked.  The caller must take care of that, if
+ * appropriate.
+ */
+static void __d_shrink(struct dentry *dentry)
+{
+	if (!d_unhashed(dentry)) {
+		struct hlist_bl_head *b;
+		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
+			b = &dentry->d_sb->s_anon;
+		else
+			b = d_hash(dentry->d_parent, dentry->d_name.hash);
+
+		hlist_bl_lock(b);
+		__hlist_bl_del(&dentry->d_hash);
+		dentry->d_hash.pprev = NULL;
+		hlist_bl_unlock(b);
+	}
+}
+
 /**
  * d_drop - drop a dentry
  * @dentry: dentry to drop
@@ -319,17 +340,7 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
 void __d_drop(struct dentry *dentry)
 {
 	if (!d_unhashed(dentry)) {
-		struct hlist_bl_head *b;
-		if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
-			b = &dentry->d_sb->s_anon;
-		else
-			b = d_hash(dentry->d_parent, dentry->d_name.hash);
-
-		hlist_bl_lock(b);
-		__hlist_bl_del(&dentry->d_hash);
-		dentry->d_hash.pprev = NULL;
-		hlist_bl_unlock(b);
-
+		__d_shrink(dentry);
 		dentry_rcuwalk_barrier(dentry);
 	}
 }
@@ -784,6 +795,7 @@ relock:
 
 /**
  * prune_dcache_sb - shrink the dcache
+ * @sb: superblock
  * @nr_to_scan: number of entries to try to free
  *
  * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
@@ -828,44 +840,24 @@ EXPORT_SYMBOL(shrink_dcache_sb);
 static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 {
 	struct dentry *parent;
-	unsigned detached = 0;
 
 	BUG_ON(!IS_ROOT(dentry));
 
-	/* detach this root from the system */
-	spin_lock(&dentry->d_lock);
-	dentry_lru_del(dentry);
-	__d_drop(dentry);
-	spin_unlock(&dentry->d_lock);
-
 	for (;;) {
 		/* descend to the first leaf in the current subtree */
-		while (!list_empty(&dentry->d_subdirs)) {
-			struct dentry *loop;
-
-			/* this is a branch with children - detach all of them
-			 * from the system in one go */
-			spin_lock(&dentry->d_lock);
-			list_for_each_entry(loop, &dentry->d_subdirs,
-					    d_u.d_child) {
-				spin_lock_nested(&loop->d_lock,
-						DENTRY_D_LOCK_NESTED);
-				dentry_lru_del(loop);
-				__d_drop(loop);
-				spin_unlock(&loop->d_lock);
-			}
-			spin_unlock(&dentry->d_lock);
-
-			/* move to the first child */
+		while (!list_empty(&dentry->d_subdirs))
 			dentry = list_entry(dentry->d_subdirs.next,
 					    struct dentry, d_u.d_child);
-		}
 
 		/* consume the dentries from this leaf up through its parents
 		 * until we find one with children or run out altogether */
 		do {
 			struct inode *inode;
 
+			/* detach from the system */
+			dentry_lru_del(dentry);
+			__d_shrink(dentry);
+
 			if (dentry->d_count != 0) {
 				printk(KERN_ERR
 				       "BUG: Dentry %p{i=%lx,n=%s}"
@@ -886,14 +878,10 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 				list_del(&dentry->d_u.d_child);
 			} else {
 				parent = dentry->d_parent;
-				spin_lock(&parent->d_lock);
 				parent->d_count--;
 				list_del(&dentry->d_u.d_child);
-				spin_unlock(&parent->d_lock);
 			}
 
-			detached++;
-
 			inode = dentry->d_inode;
 			if (inode) {
 				dentry->d_inode = NULL;
@@ -938,9 +926,7 @@ void shrink_dcache_for_umount(struct super_block *sb)
 
 	dentry = sb->s_root;
 	sb->s_root = NULL;
-	spin_lock(&dentry->d_lock);
 	dentry->d_count--;
-	spin_unlock(&dentry->d_lock);
 	shrink_dcache_for_umount_subtree(dentry);
 
 	while (!hlist_bl_empty(&sb->s_anon)) {
@@ -1743,7 +1729,7 @@ seqretry:
 		 */
 		if (read_seqcount_retry(&dentry->d_seq, *seq))
 			goto seqretry;
-		if (parent->d_flags & DCACHE_OP_COMPARE) {
+		if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
 			if (parent->d_op->d_compare(parent, *inode,
 						dentry, i,
 						tlen, tname, name))
@@ -2138,8 +2124,9 @@ static void dentry_unlock_parents_for_move(struct dentry *dentry,
  * @target: new dentry
  *
  * Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way.  Caller hold
- * rename_lock.
+ * dcache entries should not be moved in this way. Caller must hold
+ * rename_lock, the i_mutex of the source and target directories,
+ * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
  */
 static void __d_move(struct dentry * dentry, struct dentry * target)
 {
@@ -2202,7 +2189,8 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
  * @target: new dentry
  *
  * Update the dcache to reflect the move of a file name. Negative
- * dcache entries should not be moved in this way.
+ * dcache entries should not be moved in this way. See the locking
+ * requirements for __d_move.
  */
 void d_move(struct dentry *dentry, struct dentry *target)
 {
@@ -2320,7 +2308,8 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
  * @inode: inode to bind to the dentry, to which aliases may be attached
  *
  * Introduces an dentry into the tree, substituting an extant disconnected
- * root directory alias in its place if there is one
+ * root directory alias in its place if there is one. Caller must hold the
+ * i_mutex of the parent directory.
  */
 struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 {