Add async objs list for
- promote_op
- bch_read_bio
- btree_read_bio
- btree_write_bio

This gets us introspection on in-flight async ops, and because under the
hood it uses fast_lists (percpu slot buffer on top of a radix tree),
it'll be fast enough to enable in production.

This will be very helpful for debugging "something got stuck" issues,
which have been cropping up from time to time (in the CI, especially
with folio writeback).

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

There's something going on with the data move path; log the original key
being moved for debugging.

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

Add a new data op to walk all data and metadata in a filesystem,
checking if it can be read successfully, and on error repairing from
another copy if possible.

- New helper: bch2_dev_idx_is_online(), so that we can bail out and
  report to userspace when we're unable to scrub because the device is
  offline

- data_update_opts, which controls the data move path, now understands
  scrub: data is only read, not written. The read path is responsible
  for rewriting on read error, as with other reads.

- scrub_pred skips data extents that don't have checksums

- bch_ioctl_data has a new scrub member, which has a data_types field
  for data types to check - i.e. all data types, or only metadata.

- Add new entries to bch_move_stats so that we can report numbers for
  corrected and uncorrected errors

- Add a new enum to bch_ioctl_data_event for explicitly reporting
  completion and return code (i.e. device offline)

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

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

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

Add a new helper for bch2_moving_ctxt_to_text(), which may be used to
debug if moving_ios are getting stuck.

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

We had a bug report where the data update path was creating an extent
that failed to validate because it had too many pointers; almost all of
them were cached.

To fix this, we have:
- want_cached_ptr(), a new helper that checks if we even want a cached
  pointer (is on appropriate target, device is readable).

- bch2_extent_set_ptr_cached() now only sets a pointer cached if we want
  it.

- bch2_extent_normalize_by_opts() now ensures that we only have a single
  cached pointer that we want.

While working on this, it was noticed that this doesn't work well with
reflinked data and per-file options. Another patch series is coming that
plumbs through additional io path options through bch_extent_rebalance,
with improved option handling.

Reported-by: Reed Riley <reed@riley.engineer>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

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

Previously, there was a bug where if an extent had greater durability
than required (because we needed to move a durability=1 pointer and
ended up putting it on a durability 2 device), we would submit a write
for replicas=2 - the durability of the pointer being rewritten - instead
of the number of replicas required to bring it back up to the
data_replicas option.

This, plus the allocation path sometimes allocating on a greater
durability device than requested, meant that extents could continue
having more and more replicas added as they were being rewritten.

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

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