The next patch will be adding a disk accounting counter type which is
not kept in the in-memory eytzinger tree.

As prep, fold __bch2_accounting_mem_mod() into
bch2_accounting_mem_mod_locked() so that we can check for that counter
type and bail out without calling bpos_to_disk_accounting_pos() twice.

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

bkey_fsck_err() was added as an interface that looks like fsck_err(),
but previously all it did was ensure that the appropriate error counter
was incremented in the superblock.

This is a cleanup and bugfix patch that converts it to a wrapper around
fsck_err(). This is needed to fix an issue with the upgrade path to
disk_accounting_v3, where the "silent fix" error list now includes
bkey_fsck errors; fsck_err() handles this in a unified way, and since we
need to change printing of bkey fsck errors from the caller to the inner
bkey_fsck_err() calls, this ends up being a pretty big change.

Als,, rename .invalid() methods to .validate(), for clarity, while we're
changing the function signature anyways (to drop the printbuf argument).

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

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

This helps ensure key cache reclaim isn't contending with threads
waiting for the key cache to be helped, and fixes a severe performance
bug.

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

As part of improving btree key cache coherency, the bkey_cached.valid
flag is going away.

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

gc_pos is now based on keys, not nodes, for invariantness w.r.t. splits
and merges

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

Make things more consistent and ensure that we're using u64 bitfields -
key types and btree ids are already around 32 bits.

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

the order in which btree_gc walks keys have changed, so we no longer
have the sort of issues with online fsck this assertion was warning
about.

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

Rewrite fsck/gc for the new accounting scheme.

This adds a second set of in-memory accounting counters for gc to use;
like with other parts of gc we run all trigger in TRIGGER_GC mode, then
compare what we calculated to existing in-memory accounting at the end.

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

Main part of the disk accounting rewrite.

This is a wholesale rewrite of the existing disk space accounting, which
relies on percepu counters that are sharded by journal buffer, and
rolled up and added to each journal write.

With the new scheme, every set of counters is a distinct key in the
accounting btree; this fixes scaling limitations of the old scheme,
where counters took up space in each journal entry and required multiple
percpu counters.

Now, in memory accounting requires a single set of percpu counters - not
multiple for each in flight journal buffer - and in the future we'll
probably also have counters that don't use in memory percpu counters,
they're not strictly required.

An accounting update is now a normal btree update, using the btree write
buffer path. At transaction commit time, we apply accounting updates to
the in memory counters, which are percpu counters indexed in an
eytzinger tree by the accounting key.

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