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btrfs-progs: ctree: introduce function to create an empty tree

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Introduce a new function, btrfs_create_tree(), to create an empty tree.

Currently, there is only one caller to create new tree, namely data
reloc tree in mkfs.  However it's copying fs tree to create a new root.

This copy fs tree method is not a good idea if we only need an empty
tree.

So here introduce a new function, btrfs_create_tree() to create new tree.
Which will handle the following things:

1) New tree root leaf
   Using generic tree allocation

2) New root item in tree root

3) Modify special tree root pointers in fs_info
   Only quota_root is supported yet, but can be expended easily

This patch provides the basis to implement quota support in mkfs.

Signed-off-by: Qu Wenruo <wqu@suse.com>
[ solved minor conflicts ]
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2020-03-18 17:21:43 -03:00 committed by David Sterba
parent ca4cbfaba5
commit e0e047f292
2 changed files with 109 additions and 1 deletions
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108
ctree.c
View File

@ -21,8 +21,9 @@
#include "print-tree.h"
#include "repair.h"
#include "common/internal.h"
#include "kernel-lib/sizes.h"
#include "common/messages.h"
#include "common/utils.h"
#include "kernel-lib/sizes.h"
#include "volumes.h"
static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
@ -182,6 +183,111 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
return 0;
}
/*
* Create a new tree root, with root objectid set to @objectid.
*
* NOTE: Doesn't support tree with non-zero offset, like data reloc tree.
*/
int btrfs_create_root(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 objectid)
{
struct extent_buffer *node;
struct btrfs_root *new_root;
struct btrfs_disk_key disk_key;
struct btrfs_key location;
struct btrfs_root_item root_item = { 0 };
int ret;
new_root = malloc(sizeof(*new_root));
if (!new_root)
return -ENOMEM;
btrfs_setup_root(new_root, fs_info, objectid);
if (!is_fstree(objectid))
new_root->track_dirty = 1;
add_root_to_dirty_list(new_root);
new_root->objectid = objectid;
new_root->root_key.objectid = objectid;
new_root->root_key.type = BTRFS_ROOT_ITEM_KEY;
new_root->root_key.offset = 0;
node = btrfs_alloc_free_block(trans, new_root, fs_info->nodesize,
objectid, &disk_key, 0, 0, 0);
if (IS_ERR(node)) {
ret = PTR_ERR(node);
error("failed to create root node for tree %llu: %d (%m)",
objectid, ret);
return ret;
}
new_root->node = node;
btrfs_set_header_generation(node, trans->transid);
btrfs_set_header_backref_rev(node, BTRFS_MIXED_BACKREF_REV);
btrfs_clear_header_flag(node,
BTRFS_HEADER_FLAG_RELOC | BTRFS_HEADER_FLAG_WRITTEN);
btrfs_set_header_owner(node, objectid);
btrfs_set_header_nritems(node, 0);
btrfs_set_header_level(node, 0);
ret = btrfs_inc_ref(trans, new_root, node, 0);
if (ret < 0)
goto free;
/*
* Special tree roots may need to modify pointers in @fs_info
* Only quota is supported yet.
*/
switch (objectid) {
case BTRFS_QUOTA_TREE_OBJECTID:
if (fs_info->quota_root) {
error("quota root already exists");
ret = -EEXIST;
goto free;
}
fs_info->quota_root = new_root;
fs_info->quota_enabled = 1;
break;
/*
* Essential trees can't be created by this function, yet.
* As we expect such skeleton exists, or a lot of functions like
* btrfs_alloc_free_block() doesn't work at all
*/
case BTRFS_ROOT_TREE_OBJECTID:
case BTRFS_EXTENT_TREE_OBJECTID:
case BTRFS_CHUNK_TREE_OBJECTID:
case BTRFS_FS_TREE_OBJECTID:
ret = -EEXIST;
goto free;
default:
/* Subvolume trees don't need special handling */
if (is_fstree(objectid))
break;
/* Other special trees are not supported yet */
ret = -ENOTTY;
goto free;
}
btrfs_mark_buffer_dirty(node);
btrfs_set_root_bytenr(&root_item, btrfs_header_bytenr(node));
btrfs_set_root_level(&root_item, 0);
btrfs_set_root_generation(&root_item, trans->transid);
btrfs_set_root_dirid(&root_item, 0);
btrfs_set_root_refs(&root_item, 1);
btrfs_set_root_used(&root_item, fs_info->nodesize);
location.objectid = objectid;
location.type = BTRFS_ROOT_ITEM_KEY;
location.offset = 0;
ret = btrfs_insert_root(trans, fs_info->tree_root, &location, &root_item);
if (ret < 0)
goto free;
return ret;
free:
free_extent_buffer(node);
free(new_root);
return ret;
}
/*
* check if the tree block can be shared by multiple trees
*/

2
ctree.h
View File

@ -2642,6 +2642,8 @@ int btrfs_copy_root(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct extent_buffer *buf,
struct extent_buffer **cow_ret, u64 new_root_objectid);
int btrfs_create_root(struct btrfs_trans_handle *trans,
struct btrfs_fs_info *fs_info, u64 objectid);
int btrfs_extend_item(struct btrfs_root *root, struct btrfs_path *path,
u32 data_size);
int btrfs_truncate_item(struct btrfs_root *root, struct btrfs_path *path,