ubifs: split allocation of ubifs_info into a separate function

preparation to ubifs sget() race fixes
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ubifs/super.c

@@ -1971,17 +1971,12 @@ static struct ubi_volume_desc *open_ubi(const char *name, int mode)
 	return ERR_PTR(-EINVAL);
 }
 
-static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
+static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi)
 {
-	struct ubi_volume_desc *ubi = sb->s_fs_info;
 	struct ubifs_info *c;
-	struct inode *root;
-	int err;
 
 	c = kzalloc(sizeof(struct ubifs_info), GFP_KERNEL);
-	if (!c)
-		return -ENOMEM;
-
+	if (c) {
 		spin_lock_init(&c->cnt_lock);
 		spin_lock_init(&c->cs_lock);
 		spin_lock_init(&c->buds_lock);
@@ -2014,13 +2009,27 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
 		INIT_LIST_HEAD(&c->orph_new);
 		c->no_chk_data_crc = 1;
 
-	c->vfs_sb = sb;
 		c->highest_inum = UBIFS_FIRST_INO;
 		c->lhead_lnum = c->ltail_lnum = UBIFS_LOG_LNUM;
 
 		ubi_get_volume_info(ubi, &c->vi);
 		ubi_get_device_info(c->vi.ubi_num, &c->di);
+	}
+	return c;
+}
 
+static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct ubi_volume_desc *ubi = sb->s_fs_info;
+	struct ubifs_info *c;
+	struct inode *root;
+	int err;
+
+	c = alloc_ubifs_info(ubi);
+	if (!c)
+		return -ENOMEM;
+
+	c->vfs_sb = sb;
 	/* Re-open the UBI device in read-write mode */
 	c->ubi = ubi_open_volume(c->vi.ubi_num, c->vi.vol_id, UBI_READWRITE);
 	if (IS_ERR(c->ubi)) {