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

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

Continuing on with the self healing theme, we should be running any
check and repair code at runtime that we can - instead of declaring the
filesystemt inconsistent.

This will also let us skip running the backpointers -> extents fsck pass
except in debug mode.

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

Instead of walking every extent and every backpointer it points to,
first sum up backpointers in each bucket and check for mismatches, and
only look for missing backpointers if mismatches were detected, and only
check extents in those buckets.

This is a major fsck scalability improvement, since the two backpointers
passes (backpointers -> extents and extents -> backpointers) are the
most expensive fsck passes by far.

Additionally, to speed up the upgrade for backpointer bucket gens, or in
situations when we have to rebuild alloc info, add a special case for
when no backpointers are found in a bucket - don't check each individual
backpointer (in particular, avoiding the write buffer flushes), just
recreate them.

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

In an upcoming patch bch2_backpointer_get_key() will be repairing when
it finds a dangling backpointer; it will need to flush the btree write
buffer before it can definitively say there's an error.

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

bch_backpointer no longer contains the bucket_offset field, it's just a
direct LBA mapping (with low bits to account for compressed extent
splitting), so we don't need to refer to the device to construct it
anymore.

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

New on disk format version: backpointers new include the generation
number of the bucket they refer to, and the obsolete bucket_offset field
(no longer needed because we no longer store backpointers in alloc keys)
is gone.

This is an expensive forced upgrade - hopefully the last; we have to run
the extents_to_backpointers recovery pass to regenerate backpointers.

It's a forced incompatible upgrade because the alternative would've been
permamently making backpointers bigger, and as one of the biggest btrees
(along with the extents btree) that's not an ideal option.

It's worth it though, because this allows us to make the
check_extents_to_backpointers pass drastically cheaper: an upcoming
patch changes it to sum up backpointers in a bucket and check the sum
against the sector counts for that bucket, only looking for missing
backpointers if they don't match (and then only for specific buckets).

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

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

Reported-by: syzbot+997f0573004dcb964555@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add a new parameter to bkey validate functions, and use it to improve
invalid bkey error messages: we can now print the btree and depth it
came from, or if it came from the journal, or is a btree root.

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