btrfs: remove folio checked subpage bitmap tracking

The folio checked flag is only utilized by the COW fixup mechanism
inside btrfs.

Since the COW fixup is already removed from non-experimental builds,
there is no need to keep the checked subpage bitmap.

This will saves us some space for large folios, for example for a single
256K sized large folio on 4K page sized systems:

 Old bitmap size = 6 * (256K / 4K / 8) = 48 bytes
 New bitmap size = 5 * (256K / 4K / 8) = 40 bytes

This will be more obvious when we're going to support huge folios (order
= 9).

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions