ca->io_ref does not protect against the filesystem going way,
c->write_ref does. Much like

0b50b7313ef2 bcachefs: Fix refcounting in discard path

the other async paths need fixing.

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

bch_dev->io_ref does not protect against the filesystem going away;
bch_fs->writes does.

Thus the filesystem write ref needs to be the last ref we release.

Reported-by: syzbot+9e0404b505e604f67e41@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

we allow new fields to be added to existing key types, and new versions
should treat them as being zeroed; this was not handled in
alloc_v4_validate.

Reported-by: syzbot+3b2968fa4953885dd66a@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Comparing the wrong bpos - this was missed because normally
bucket_gens_init() runs on brand new filesystems, but this bug caused it
to overwrite bucket_gens keys with 0s when upgrading ancient
filesystems.

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

On testing on an old mangled filesystem, we missed a case.

Fixes: bd864bc2d907 ("bcachefs: Fix bch2_trigger_alloc when upgrading from old versions")
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>

bch2_trigger_alloc was assuming that the new key would always be newly
created and thus always an alloc_v4 key, but - not when called from
btree_gc.

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

This fixes an accounting mismatch for cached data.

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

gc_lock is now only for synchronization between check_alloc_info and
interior btree updates - nothing else

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

fsck_err() now optionally takes a btree_trans; if the current thread has
one, it is required that it be passed.

The next patch will use this to unlock when waiting for user input.

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