bcachefs: Add a feature bit for indicating fs has no alloc info WIP

If a filesystem is going to only be used read-only, and will be a
deployable image, we can strip out alloc info for a substantial
reduction in metadata size - around half, due to backpointers.

Alloc info will be regenerated on first read-write mount.

Remounting RW is disallowed for now, since we don't yet have
check_allocations running in RW mode.

XXX make scrub work (no repair)
XXX look at mount wall clock time/profile

XXX we also really don't want to be pinning btree roots in memory
anymore, since a lot of them aren't used

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

0 files changed, 0 insertions, 0 deletions