Fsck wants to do transaction commits from an outer context; it may have
other repair to do (i.e. duplicate backpointers).

But when calling backpointer_not_found() from runtime code, i.e. runtime
self healing, we should be doing the commit - the outer context expects
to just be doing lookups.

This fixes bugs where we get stuck spinning, reported as "RCU lock hold
time warnings.

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

peek_slot() doesn't normally return bkey_s_c_null - except when we ask
for a key at a btree level that doesn't exist, which can happen here.

We might want to revisit this, but we'll have to look over all the
places where we use peek_slot() on interior nodes.

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

This was planned to be done ages ago, now finally completed; there are
places where we have quite a few btree_trans objects on the stack, so
this reduces stack usage somewhat.

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

We now have separate per device io_refs for read and write access.

This fixes a device removal bug where the discard workers were still
running while we're removing alloc info for that device.

It's also a bit of hardening; we no longer allow writes to devices that
are read-only.

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

Build up and emit the error message for an inconsistency error all at
once, instead of spread over multiple printk calls, so they're not
jumbled in the dmesg log.

Also, add better indenting.

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

Add the new helper printbuf_indent_add_nextline(), and use it in
__bch2_fsck_err() to centralize setting the indentation of multiline
fsck errors.

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

state_lock guards against devices coming or leaving, changing state, or
the filesystem changing between ro <-> rw.

But it's not necessary for running recovery passes, and holding it
blocks asynchronous events that would cause us to go RO or kick out
devices.

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

New data types might be added later, so we don't want to disallow
unknown data types - that'll be a compatibility hassle later. Instead,
ignore them.

Reported-by: syzbot+3a290f5ff67ca3023834@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

These are counted as stripe data in the corresponding alloc keys.

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

Cached pointers now have backpointers.

This means that we'll be able to kill cached pointers in the
bucket_invalidate path, when invalidating/reusing buckets containing
cached data, instead of leaving them around to be cleaned up by gc_gens
garbago collection - which requires a full metadata scan.

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