btrfs: remove unused extent state bits

The last users are long gone.

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: use enum for wq endio metadata type

The enum exists but is not consistently used.

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: fix error labels in init_btrfs_fs

btrfs_interface_init rarely fails but we could leak the prelim_ref slab.

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: use slab for end_io_wq structures

The structure is frequently reused.  Rename it according to the slab
name.

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: remove unused members from struct scrub_warning

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: let merge_reloc_roots return void

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: hide typecast to definition of BTRFS_SEND_TRANS_STUB

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: drop constant param from btrfs_release_extent_buffer_page

All callers use the same value, simplify the function.

Signed-off-by: David Sterba <dsterba@suse.cz>
btrfs: kill extent_buffer_page helper

It used to be more complex but now it's just a simple array access.

Signed-off-by: David Sterba <dsterba@suse.cz>