bcachefs: bch2_kthread_io_clock_wait() no longer sleeps until full amount

Drop t he loop in bch2_kthread_io_clock_wait(): this allows the code
that uses it to be woken up for other reasons, and fixes a bug where
rebalance wouldn't wake up when a scan was requested.

This raises the possibility of spurious wakeups, but callers should
always be able to handle that reasonably well.

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

bcachefs: Private error codes: ENOMEM

This adds private error codes for most (but not all) of our ENOMEM uses,
which makes it easier to track down assorted allocation failures.

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

bcachefs: Printbuf rework

This converts bcachefs to the modern printbuf interface/implementation,
synced with the version to be submitted upstream.

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

bcachefs: Heap allocate printbufs

This patch changes printbufs dynamically allocate and reallocate a
buffer as needed. Stack usage has become a bit of a problem, and a major
cause of that has been static size string buffers on the stack.

The most involved part of this refactoring is that printbufs must now be
exited with printbuf_exit().

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

bcachefs: Persist 64 bit io clocks

Originally, bcachefs - going back to bcache - stored, for each bucket, a
16 bit counter corresponding to how long it had been since the bucket
was read from. But, this required periodically rescaling counters on
every bucket to avoid wraparound. That wasn't an issue in bcache, where
we'd perodically rewrite the per bucket metadata all at once, but in
bcachefs we're trying to avoid having to walk every single bucket.

This patch switches to persisting 64 bit io clocks, corresponding to the
64 bit bucket timestaps introduced in the previous patch with
KEY_TYPE_alloc_v2.

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

bcachefs: Convert various code to printbuf

printbufs know how big the buffer is that was allocated, so we can get
rid of the random PAGE_SIZEs all over the place.

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

bcachefs: Add debug code to print btree transactions

Intented to help debug deadlocks, since we can't use lockdep to check
btree node lock ordering.

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

bcachefs: Make io timers less buggy

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

bcachefs: Inline fast path of bch2_increment_clock()

Shaving more cycles.

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

bcachefs: add functionality for heaps to update backpointers

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

bcachefs: Initial commit

Initially forked from drivers/md/bcache, bcachefs is a new copy-on-write
filesystem with every feature you could possibly want.

Website: https://bcachefs.org

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