3 files changed, 51 insertions, 27 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 7ecfe95..9d0ef5e1 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -177,22 +177,6 @@ static int fuse_dentry_revalidate(struct dentry *entry, struct nameidata *nd)
 	return 1;
 }
 
-/*
- * Check if there's already a hashed alias of this directory inode.
- * If yes, then lookup and mkdir must not create a new alias.
- */
-static int dir_alias(struct inode *inode)
-{
-	if (S_ISDIR(inode->i_mode)) {
-		struct dentry *alias = d_find_alias(inode);
-		if (alias) {
-			dput(alias);
-			return 1;
-		}
-	}
-	return 0;
-}
-
 static int invalid_nodeid(u64 nodeid)
 {
 	return !nodeid || nodeid == FUSE_ROOT_ID;
@@ -208,6 +192,24 @@ static int valid_mode(int m)
 		S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
 }
 
+/*
+ * Add a directory inode to a dentry, ensuring that no other dentry
+ * refers to this inode.  Called with fc->inst_mutex.
+ */
+static int fuse_d_add_directory(struct dentry *entry, struct inode *inode)
+{
+	struct dentry *alias = d_find_alias(inode);
+	if (alias) {
+		/* This tries to shrink the subtree below alias */
+		fuse_invalidate_entry(alias);
+		dput(alias);
+		if (!list_empty(&inode->i_dentry))
+			return -EBUSY;
+	}
+	d_add(entry, inode);
+	return 0;
+}
+
 static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 				  struct nameidata *nd)
 {
@@ -243,11 +245,17 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 	if (err && err != -ENOENT)
 		return ERR_PTR(err);
 
-	if (inode && dir_alias(inode)) {
-		iput(inode);
-		return ERR_PTR(-EIO);
-	}
-	d_add(entry, inode);
+	if (inode && S_ISDIR(inode->i_mode)) {
+		mutex_lock(&fc->inst_mutex);
+		err = fuse_d_add_directory(entry, inode);
+		mutex_unlock(&fc->inst_mutex);
+		if (err) {
+			iput(inode);
+			return ERR_PTR(err);
+		}
+	} else
+		d_add(entry, inode);
+
 	entry->d_op = &fuse_dentry_operations;
 	if (!err)
 		fuse_change_timeout(entry, &outarg);
@@ -403,12 +411,22 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req,
 	}
 	fuse_put_request(fc, req);
 
-	if (dir_alias(inode)) {
-		iput(inode);
-		return -EIO;
-	}
+	if (S_ISDIR(inode->i_mode)) {
+		struct dentry *alias;
+		mutex_lock(&fc->inst_mutex);
+		alias = d_find_alias(inode);
+		if (alias) {
+			/* New directory must have moved since mkdir */
+			mutex_unlock(&fc->inst_mutex);
+			dput(alias);
+			iput(inode);
+			return -EBUSY;
+		}
+		d_instantiate(entry, inode);
+		mutex_unlock(&fc->inst_mutex);
+	} else
+		d_instantiate(entry, inode);
 
-	d_instantiate(entry, inode);
 	fuse_change_timeout(entry, &outarg);
 	fuse_invalidate_attr(dir);
 	return 0;
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 69c7750..91edb89 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -239,6 +239,9 @@ struct fuse_conn {
 	/** Lock protecting accessess to  members of this structure */
 	spinlock_t lock;
 
+	/** Mutex protecting against directory alias creation */
+	struct mutex inst_mutex;
+
 	/** Refcount */
 	atomic_t count;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 4ee8f72..fc42035 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -379,6 +379,7 @@ static struct fuse_conn *new_conn(void)
 	fc = kzalloc(sizeof(*fc), GFP_KERNEL);
 	if (fc) {
 		spin_lock_init(&fc->lock);
+		mutex_init(&fc->inst_mutex);
 		atomic_set(&fc->count, 1);
 		init_waitqueue_head(&fc->waitq);
 		init_waitqueue_head(&fc->blocked_waitq);
@@ -398,8 +399,10 @@ static struct fuse_conn *new_conn(void)
 
 void fuse_conn_put(struct fuse_conn *fc)
 {
-	if (atomic_dec_and_test(&fc->count))
+	if (atomic_dec_and_test(&fc->count)) {
+		mutex_destroy(&fc->inst_mutex);
 		kfree(fc);
+	}
 }
 
 struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)