staging: erofs: kill all failure handling in fill_super()

.kill_sb() will do that instead in order to remove duplicated code.

Note that the initialzation of managed_cache is now moved
after s_root is assigned since it's more preferred to iput()
in .put_super() and all inodes should be evicted before
the end of generic_shutdown_super(sb).
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-12-gaoxiang25@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/erofs/super.c

@@ -343,12 +343,13 @@ static const struct address_space_operations managed_cache_aops = {
 	.invalidatepage = managed_cache_invalidatepage,
 };
 
-static struct inode *erofs_init_managed_cache(struct super_block *sb)
+static int erofs_init_managed_cache(struct super_block *sb)
 {
-	struct inode *inode = new_inode(sb);
+	struct erofs_sb_info *const sbi = EROFS_SB(sb);
+	struct inode *const inode = new_inode(sb);
 
 	if (unlikely(!inode))
-		return ERR_PTR(-ENOMEM);
+		return -ENOMEM;
 
 	set_nlink(inode, 1);
 	inode->i_size = OFFSET_MAX;
@@ -357,37 +358,38 @@ static struct inode *erofs_init_managed_cache(struct super_block *sb)
 	mapping_set_gfp_mask(inode->i_mapping,
 			     GFP_NOFS | __GFP_HIGHMEM |
 			     __GFP_MOVABLE |  __GFP_NOFAIL);
-	return inode;
+	sbi->managed_cache = inode;
+	return 0;
 }
-
+#else
+static int erofs_init_managed_cache(struct super_block *sb) { return 0; }
 #endif
 
 static int erofs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode *inode;
 	struct erofs_sb_info *sbi;
-	int err = -EINVAL;
+	int err;
 
 	infoln("fill_super, device -> %s", sb->s_id);
 	infoln("options -> %s", (char *)data);
 
+	sb->s_magic = EROFS_SUPER_MAGIC;
+
 	if (unlikely(!sb_set_blocksize(sb, EROFS_BLKSIZ))) {
 		errln("failed to set erofs blksize");
-		goto err;
+		return -EINVAL;
 	}
 
 	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
-	if (unlikely(!sbi)) {
-		err = -ENOMEM;
-		goto err;
-	}
-	sb->s_fs_info = sbi;
+	if (unlikely(!sbi))
+		return -ENOMEM;
 
+	sb->s_fs_info = sbi;
 	err = superblock_read(sb);
 	if (err)
-		goto err_sbread;
+		return err;
 
-	sb->s_magic = EROFS_SUPER_MAGIC;
 	sb->s_flags |= SB_RDONLY | SB_NOATIME;
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_time_gran = 1;
@@ -397,13 +399,12 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
 #ifdef CONFIG_EROFS_FS_XATTR
 	sb->s_xattr = erofs_xattr_handlers;
 #endif
-
 	/* set erofs default mount options */
 	default_options(sbi);
 
 	err = parse_options(sb, data);
-	if (err)
-		goto err_parseopt;
+	if (unlikely(err))
+		return err;
 
 	if (!silent)
 		infoln("root inode @ nid %llu", ROOT_NID(sbi));
@@ -417,93 +418,78 @@ static int erofs_fill_super(struct super_block *sb, void *data, int silent)
 	INIT_RADIX_TREE(&sbi->workstn_tree, GFP_ATOMIC);
 #endif
 
-#ifdef EROFS_FS_HAS_MANAGED_CACHE
-	sbi->managed_cache = erofs_init_managed_cache(sb);
-	if (IS_ERR(sbi->managed_cache)) {
-		err = PTR_ERR(sbi->managed_cache);
-		goto err_init_managed_cache;
-	}
-#endif
-
 	/* get the root inode */
 	inode = erofs_iget(sb, ROOT_NID(sbi), true);
-	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
-		goto err_iget;
-	}
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
 
-	if (!S_ISDIR(inode->i_mode)) {
+	if (unlikely(!S_ISDIR(inode->i_mode))) {
 		errln("rootino(nid %llu) is not a directory(i_mode %o)",
 		      ROOT_NID(sbi), inode->i_mode);
-		err = -EINVAL;
 		iput(inode);
-		goto err_iget;
+		return -EINVAL;
 	}
 
 	sb->s_root = d_make_root(inode);
-	if (!sb->s_root) {
-		err = -ENOMEM;
-		goto err_iget;
-	}
+	if (unlikely(!sb->s_root))
+		return -ENOMEM;
 
 	erofs_shrinker_register(sb);
+	/* sb->s_umount is already locked, SB_ACTIVE and SB_BORN are not set */
+	err = erofs_init_managed_cache(sb);
+	if (unlikely(err))
+		return err;
 
 	if (!silent)
 		infoln("mounted on %s with opts: %s.", sb->s_id, (char *)data);
 	return 0;
-	/*
-	 * please add a label for each exit point and use
-	 * the following name convention, thus new features
-	 * can be integrated easily without renaming labels.
-	 */
-err_iget:
-#ifdef EROFS_FS_HAS_MANAGED_CACHE
-	iput(sbi->managed_cache);
-err_init_managed_cache:
-#endif
-err_parseopt:
-err_sbread:
-	sb->s_fs_info = NULL;
-	kfree(sbi);
-err:
-	return err;
+}
+
+static struct dentry *erofs_mount(struct file_system_type *fs_type, int flags,
+				  const char *dev_name, void *data)
+{
+	return mount_bdev(fs_type, flags, dev_name, data, erofs_fill_super);
 }
 
 /*
  * could be triggered after deactivate_locked_super()
  * is called, thus including umount and failed to initialize.
  */
-static void erofs_put_super(struct super_block *sb)
+static void erofs_kill_sb(struct super_block *sb)
 {
-	struct erofs_sb_info *sbi = EROFS_SB(sb);
+	struct erofs_sb_info *sbi;
+
+	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
+	infoln("unmounting for %s", sb->s_id);
 
-	/* for cases which are failed in "read_super" */
+	kill_block_super(sb);
+
+	sbi = EROFS_SB(sb);
 	if (!sbi)
 		return;
+	kfree(sbi);
+	sb->s_fs_info = NULL;
+}
 
-	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
+/* called when ->s_root is non-NULL */
+static void erofs_put_super(struct super_block *sb)
+{
+	struct erofs_sb_info *const sbi = EROFS_SB(sb);
 
-	infoln("unmounted for %s", sb->s_id);
+	DBG_BUGON(!sbi);
 
 	erofs_shrinker_unregister(sb);
 #ifdef EROFS_FS_HAS_MANAGED_CACHE
 	iput(sbi->managed_cache);
+	sbi->managed_cache = NULL;
 #endif
-	kfree(sbi);
-	sb->s_fs_info = NULL;
-}
-
-static struct dentry *erofs_mount(struct file_system_type *fs_type, int flags,
-				  const char *dev_name, void *data)
-{
-	return mount_bdev(fs_type, flags, dev_name, data, erofs_fill_super);
 }
 
 static struct file_system_type erofs_fs_type = {
 	.owner          = THIS_MODULE,
 	.name           = "erofs",
 	.mount          = erofs_mount,
-	.kill_sb        = kill_block_super,
+	.kill_sb        = erofs_kill_sb,
 	.fs_flags       = FS_REQUIRES_DEV,
 };
 MODULE_ALIAS_FS("erofs");