cachefiles: use path_get instead of lone dget

Dentry references should not be acquired without a corresponding
vfsmount ref.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/cachefiles/daemon.c

@@ -553,7 +553,7 @@ static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
 {
 	struct fs_struct *fs;
-	struct dentry *dir;
+	struct path path;
 	const struct cred *saved_cred;
 	int ret;
 
@@ -575,22 +575,23 @@ static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
 	/* extract the directory dentry from the cwd */
 	fs = current->fs;
 	read_lock(&fs->lock);
-	dir = dget(fs->pwd.dentry);
+	path = fs->pwd;
+	path_get(&path);
 	read_unlock(&fs->lock);
 
-	if (!S_ISDIR(dir->d_inode->i_mode))
+	if (!S_ISDIR(path.dentry->d_inode->i_mode))
 		goto notdir;
 
 	cachefiles_begin_secure(cache, &saved_cred);
-	ret = cachefiles_cull(cache, dir, args);
+	ret = cachefiles_cull(cache, path.dentry, args);
 	cachefiles_end_secure(cache, saved_cred);
 
-	dput(dir);
+	path_put(&path);
 	_leave(" = %d", ret);
 	return ret;
 
 notdir:
-	dput(dir);
+	path_put(&path);
 	kerror("cull command requires dirfd to be a directory");
 	return -ENOTDIR;
 
@@ -629,7 +630,7 @@ static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
 {
 	struct fs_struct *fs;
-	struct dentry *dir;
+	struct path path;
 	const struct cred *saved_cred;
 	int ret;
 
@@ -651,22 +652,23 @@ static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
 	/* extract the directory dentry from the cwd */
 	fs = current->fs;
 	read_lock(&fs->lock);
-	dir = dget(fs->pwd.dentry);
+	path = fs->pwd;
+	path_get(&path);
 	read_unlock(&fs->lock);
 
-	if (!S_ISDIR(dir->d_inode->i_mode))
+	if (!S_ISDIR(path.dentry->d_inode->i_mode))
 		goto notdir;
 
 	cachefiles_begin_secure(cache, &saved_cred);
-	ret = cachefiles_check_in_use(cache, dir, args);
+	ret = cachefiles_check_in_use(cache, path.dentry, args);
 	cachefiles_end_secure(cache, saved_cred);
 
-	dput(dir);
+	path_put(&path);
 	//_leave(" = %d", ret);
 	return ret;
 
 notdir:
-	dput(dir);
+	path_put(&path);
 	kerror("inuse command requires dirfd to be a directory");
 	return -ENOTDIR;