The function btrfs_mksubvol() is very different between btrfs-progs and
kernel, the former version is really just linking a subvolume to another
directory inode, but the kernel version is really to make a completely
new subvolume.
Instead of same-named function, introduce btrfs_link_subvolume() and use
it to replace the old btrfs_mksubvol().
This is done by:
- Introduce btrfs_link_subvolume()
Which does extra checks before doing any modification:
* Make sure the target inode is a directory
* Make sure no filename conflict
Then do the linkage:
* Add the dir_item/dir_index into the parent inode
* Add the forward and backward root refs into tree root
- Introduce link_image_subvolume() helper
Currently btrfs_mksubvol() has a dedicated convert filename retry
behavior, which is unnecessary and should be done by the convert code.
Now move the filename retry behavior into the helper.
- Remove btrfs_mksubvol()
Since there is only one caller utilizing btrfs_mksubvol(), and it's
now gone, we can remove the old btrfs_mksubvol().
Signed-off-by: Qu Wenruo <wqu@suse.com>
There are two different subvolume/data reloc tree creation routines:
- create_subvol() from convert/main.c
* calls btrfs_copy_root() to create an empty root
This is not safe, as it relies on the source root to be empty.
* calls btrfs_read_fs_root() to add it to the cache and trace it
properly
* calls btrfs_make_root_dir() to initialize the empty new root
- create_data_reloc_tree() from mkfs/main.c
* calls btrfs_create_tree() to create an empty root
* Manually add the root to fs_root cache
This is only safe for data reloc tree as it's never updated
inside btrfs-progs.
But not safe for other subvolume trees.
* manually setup the root dir
Both have their good and bad aspects, so here we introduce a new helper,
btrfs_make_subvolume():
- Calls btrfs_create_tree() to create an empty root
- Calls btrfs_read_fs_root() to setup the cache and tracking properly
- Calls btrfs_make_root_dir() to initialize the root dir
- Calls btrfs_update_root() to reflect the rootdir change
So this new helper can replace both create_subvol() and
create_data_reloc_tree().
Signed-off-by: Qu Wenruo <wqu@suse.com>
