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

Add a tracepoint for any time we return an error and unwind.

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

The new guard(), scoped_guard() allow for more natural code.

Some of the uses with creative flow control have been left.

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

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

Detect buckets with missing backpointers, and run repair on demand.

__bch2_move_data_phys() now calls
bch2_check_bucket_backpointer_mismatch() as it walks buckets, which
checks for missing backpointers by comparing backpointers against bucket
sector counts.

When missing backpointers are detected, we kick off
bch2_check_extents_to_backpointers() asynchronously - right away if
we're trying to evacuate, or with a threshold if we're just running
copygc.

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

Add some more helpers, and mismatches is now a superset of the empty
bitmap - simplifies most checks.

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

We want recovery.curr_pass to be private to the recovery passes code,
for better showing recovery pass status; also, it may rewind and is
generally not the correct member to use.

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

bch_fs has gotten obnoxiously big, let's start organizing thins a bit
better.

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

We'd like users to be able to debug without building custom kernels, so
this will help us get rid of CONFIG_BCACHEFS_DEBUG, at least for most
things.

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

More self healing work: we're going to be calling
check_bucket_backpointer_mismatch() at runtime, outside of fsck.

Then when we need to we'll kick off the full
check_extents_to_backpointers recovery pass.

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