bch2_backpointer_get_key() returns bkey_s_c_null when the target isn't
found.

backpointer_get_key() flags the error, so there's nothing else to do
here - just skip it and move on.

Link: https://github.com/koverstreet/bcachefs/issues/847
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>

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>

We're hitting some issues with uninitialized struct padding, flagged by
kmsan.

They appear to be falso positives, otherwise bch2_accounting_validate()
would have flagged them as "junk at end". But for now, we'll need to
initialize disk_accounting_pos with memset().

This adds a new helper, bch2_disk_accounting_mod2(), that initializes a
disk_accounting_pos and does the accounting mod all at once - so overall
things actually get slightly more ergonomic.

BCH_DISK_ACCOUNTING_replicas keys are left for now; KMSAN isn't warning
about them and they're a bit special.

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

Replace these with proper private error codes, so that when we get an
error message we're not sifting through the entire codebase to see where
it came from.

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

the discard option is special, because it's both a filesystem and a
device option.

When set at the filesytsem level, it's supposed to propagate to (if set
persistently via sysfs) or override (if non persistently as a mount
option) the devices - that now works correctly.

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

Use error type alloc_v3_unpack_error in bch2_alloc_v3_validate().

Fixes: b65db750e2bb ("bcachefs: Enumerate fsck errors")
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add a persistent LRU for stripes, ordered by "number of empty blocks",
i.e. order in which we wish to reuse them.

This will replace the in-memory stripes heap, so we can kill off reading
stripes into memory at startup.

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