3 files changed, 51 insertions, 27 deletions

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 7ecfe95795cd..9d0ef5e18740 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 69c7750d55b8..91edb8932d90 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 4ee8f72e6380..fc4203570370 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)