bcachefs: bch_member.btree_allocated_bitmap

This adds a small (64 bit) per-device bitmap that tracks ranges that
have btree nodes, for accelerating btree node scan if it is ever needed.

- New helpers, bch2_dev_btree_bitmap_marked() and
bch2_dev_bitmap_mark(), for checking and updating the bitmap

- Interior btree update path updates the bitmaps when required

- The check_allocations pass has a new fsck_err check,
btree_bitmap_not_marked

- New on disk format version, mi_btree_mitmap, which indicates the new
bitmap is present

- Upgrade table lists the required recovery pass and expected fsck error

- Btree node scan uses the bitmap to skip ranges if we're on the new
version

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

bcachefs: Split out recovery_passes.c

We've grown a fair amount of code for managing recovery passes; tracking
which ones we're running, which ones need to be run, and flagging in the
superblock which ones need to be run on the next recovery.

So it's worth splitting out into its own file, this code is pretty
different from the code in recovery.c.

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

bcachefs: reconstruct_alloc cleanup

Now that we've got the errors_silent mechanism, we don't have to check
if the reconstruct_alloc option is set all over the place.

Also - users no longer have to explicitly select fsck and fix_errors.

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

bcachefs: BTREE_ID_subvolume_children

Add a btree to record a parent -> child subvolume relationships,
according to the filesystem heirarchy.

The subvolume_children btree is a bitset btree: if a bit is set at pos
p, that means p.offset is a child of subvolume p.inode.

This will be used for efficiently listing subvolumes, as well as
recursive deletion.

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

bcachefs: bch_subvolume::fs_path_parent

Record the filesystem path heirarchy for subvolumes in bch_subvolume

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

bcachefs: fsck_err()s don't need to manually check c->sb.version anymore

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

bcachefs: Upgrades now specify errors to fix, like downgrades

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

bcachefs: bch_sb_field_downgrade

Add a new superblock section that contains a list of
{ minor version, recovery passes, errors_to_fix }

that is - a list of recovery passes that must be run when downgrading
past a given version, and a list of errors to silently fix.

The upcoming disk accounting rewrite is not going to be fully
compatible: we're going to have to regenerate accounting both when
upgrading to the new version, and also from downgrading from the new
version, since the new method of doing disk space accounting is a
completely different architecture based on deltas, and synchronizing
them for every jounal entry write to maintain compatibility is going to
be too expensive and impractical.

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