[PATCH 04/16] btrfs: extract btree inode init code into its own init/exit helpers

[Qu Wenruo <wqu@suse.com>]

Just like how we handle init_btrfs_fs(), here we also use an array to
handle the open_ctree() sequence.

This patch will do the first step by introducing the arrays, and put
btree_inode init/exit code into two helpers:

- open_ctree_btree_inode_init
- open_ctree_btree_inode_exit

[EXPOSED LABEL MISMATCH]
- Bad btrfs_mapping_tree_free() call
  Currently in fail_alloc tag, we call not only iput() on btree_inode, but
  also free the fs_info->mapping_tree, which is not correct.

  As the first time we touch mapping_tree is at btrfs_read_sys_array(),
  thus the btrfs_mapping_tree_free() call is already a label mismatch.

  This will be addressed when we refactor the chunk tree init code.

- Bad invalidate_inode_pages2() call
  After initiliazing the btree inode, we should invalidate all the page
  cache for metadata before we put the btree inode.

  But the old code is calling invalidate_inode_pages2() before stopping
  all workers.

  This is addressed by this patch as we're really the last exit function
  to be executed, thus we're safe to call invalidate_inode_pages2() then
  iput().

[SPECIAL HANDLING]
After init_mount_fs_info() if we hit some error, we don't need to undo
the work of init_mount_fs_info(), as caller will call btrfs_free_fs_info()
to free it anyway.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/disk-io.c | 116 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 82 insertions(+), 34 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5fbf73daa388..79507c384146 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3290,6 +3290,69 @@ int btrfs_start_pre_rw_mount(struct btrfs_fs_info *fs_info)
 	return ret;
 }
 
+static int open_ctree_btree_inode_init(struct btrfs_fs_info *fs_info)
+{
+	int ret;
+
+	/*
+	 * The members initialized inside init_mount_fs_info() will be
+	 * handled in btrfs_free_fs_info() by the caller.
+	 * Thus we don't need to handle its error here.
+	 */
+	ret = init_mount_fs_info(fs_info);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * These need to be init'ed before we start creating inodes and such.
+	 *
+	 * And this 
+	 */
+	fs_info->tree_root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID,
+					      GFP_KERNEL);
+	fs_info->chunk_root = btrfs_alloc_root(fs_info, BTRFS_CHUNK_TREE_OBJECTID,
+					       GFP_KERNEL);
+	if (!fs_info->tree_root || !fs_info->chunk_root)
+		goto enomem;
+	fs_info->btree_inode = new_inode(fs_info->sb);
+	if (!fs_info->btree_inode)
+		goto enomem;
+
+	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
+	btrfs_init_btree_inode(fs_info);
+	invalidate_bdev(fs_info->fs_devices->latest_dev->bdev);
+	return 0;
+enomem:
+	btrfs_put_root(fs_info->tree_root);
+	btrfs_put_root(fs_info->chunk_root);
+	fs_info->tree_root = NULL;
+	fs_info->chunk_root = NULL;
+	return -ENOMEM;
+}
+
+static void open_ctree_btree_inode_exit(struct btrfs_fs_info *fs_info)
+{
+	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
+	iput(fs_info->btree_inode);
+	btrfs_put_root(fs_info->tree_root);
+	btrfs_put_root(fs_info->chunk_root);
+	fs_info->tree_root = NULL;
+	fs_info->chunk_root = NULL;
+}
+
+struct init_sequence {
+	int (*init_func)(struct btrfs_fs_info *fs_info);
+	void (*exit_func)(struct btrfs_fs_info *fs_info);
+};
+
+static const struct init_sequence open_ctree_seq[] = {
+	{
+		.init_func = open_ctree_btree_inode_init,
+		.exit_func = open_ctree_btree_inode_exit,
+	}
+};
+
+
 int __cold open_ctree(struct super_block *sb, char *options)
 {
 	u32 sectorsize;
@@ -3298,47 +3361,26 @@ int __cold open_ctree(struct super_block *sb, char *options)
 	u64 generation;
 	u64 features;
 	u16 csum_type;
+	bool open_ctree_res[ARRAY_SIZE(open_ctree_seq)] = {0};
 	struct btrfs_super_block *disk_super;
 	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
 	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
-	struct btrfs_root *tree_root;
-	struct btrfs_root *chunk_root;
 	int ret;
 	int err = -EINVAL;
 	int level;
+	int i;
 
 	fs_info->sb = sb;
 
 	/* Caller should have already initialized fs_info->fs_devices. */
 	ASSERT(fs_info->fs_devices);
 
-	ret = init_mount_fs_info(fs_info);
-	if (ret) {
-		err = ret;
-		goto fail;
-	}
-
-	/* These need to be init'ed before we start creating inodes and such. */
-	tree_root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID,
-				     GFP_KERNEL);
-	fs_info->tree_root = tree_root;
-	chunk_root = btrfs_alloc_root(fs_info, BTRFS_CHUNK_TREE_OBJECTID,
-				      GFP_KERNEL);
-	fs_info->chunk_root = chunk_root;
-	if (!tree_root || !chunk_root) {
-		err = -ENOMEM;
-		goto fail;
-	}
-
-	fs_info->btree_inode = new_inode(fs_info->sb);
-	if (!fs_info->btree_inode) {
-		err = -ENOMEM;
-		goto fail;
+	for (i = 0; i < ARRAY_SIZE(open_ctree_seq); i++) {
+		ret = open_ctree_seq[i].init_func(fs_info);
+		if (ret < 0)
+			goto fail;
+		open_ctree_res[i] = true;
 	}
-	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
-	btrfs_init_btree_inode(fs_info);
-
-	invalidate_bdev(fs_devices->latest_dev->bdev);
 
 	/*
 	 * Read super block and check the signature bytes only
@@ -3557,14 +3599,15 @@ int __cold open_ctree(struct super_block *sb, char *options)
 
 	generation = btrfs_super_chunk_root_generation(disk_super);
 	level = btrfs_super_chunk_root_level(disk_super);
-	ret = load_super_root(chunk_root, btrfs_super_chunk_root(disk_super),
+	ret = load_super_root(fs_info->chunk_root,
+			      btrfs_super_chunk_root(disk_super),
 			      generation, level);
 	if (ret) {
 		btrfs_err(fs_info, "failed to read chunk root");
 		goto fail_tree_roots;
 	}
 
-	read_extent_buffer(chunk_root->node, fs_info->chunk_tree_uuid,
+	read_extent_buffer(fs_info->chunk_root->node, fs_info->chunk_tree_uuid,
 			   offsetof(struct btrfs_header, chunk_tree_uuid),
 			   BTRFS_UUID_SIZE);
 
@@ -3688,7 +3731,7 @@ int __cold open_ctree(struct super_block *sb, char *options)
 		goto fail_sysfs;
 
 	fs_info->transaction_kthread = kthread_run(transaction_kthread,
-						   tree_root,
+						   fs_info->tree_root,
 						   "btrfs-transaction");
 	if (IS_ERR(fs_info->transaction_kthread))
 		goto fail_cleaner;
@@ -3803,17 +3846,22 @@ int __cold open_ctree(struct super_block *sb, char *options)
 	if (fs_info->data_reloc_root)
 		btrfs_drop_and_free_fs_root(fs_info, fs_info->data_reloc_root);
 	free_root_pointers(fs_info, true);
-	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 
 fail_sb_buffer:
 	btrfs_stop_all_workers(fs_info);
 	btrfs_free_block_groups(fs_info);
 fail_alloc:
 	btrfs_mapping_tree_free(&fs_info->mapping_tree);
-
-	iput(fs_info->btree_inode);
 fail:
+	for (i = ARRAY_SIZE(open_ctree_seq) - 1; i >= 0; i--) {
+		if (!open_ctree_res[i] || !open_ctree_seq[i].exit_func)
+			continue;
+		open_ctree_seq[i].exit_func(fs_info);
+		open_ctree_res[i] = false;
+	}
 	btrfs_close_devices(fs_info->fs_devices);
+	if (ret < 0)
+		err = ret;
 	return err;
 }
 ALLOW_ERROR_INJECTION(open_ctree, ERRNO);
-- 
2.37.3