PG: make the reservation sets more descriptively named

These sets won't precisely be the backfill_targets or actingbackfill
shortly.

%s/sorted_backfill_set/remote_shards_to_reserve_backfill/g
%s/acting_osd_it/remote_recovery_reservation_it/g
%s/sorted_actingbackfill_set/remote_shards_to_reserve_recovery/g

Signed-off-by: Samuel Just <sam.just@inktank.com>
PG: recover from each osd at most once

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG: create max hitset size

Otherwise, hit_set_create could create an unbounded size hitset
object.

Fixes: #9339
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
PG::choose_acting: let the pg go down if acting is smaller than min_size

Even if the backfill peer would bring us up to min_size, we can't go
active since build_prior will not consider the interval maybe_went_rw.

Fixes: #9497
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
PG::find_best_info: let history.last_epoch_started provide a lower bound

If we find a info.history.last_epoch_started above any
info.last_epoch_started, we must be missing updates and
min_last_update_acceptable should provisionally be max().

Fixes: #9482
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
Merge remote-tracking branches 'origin/wip-9497' and 'origin/wip-9482' into wip-log-crash-firefly
PGLog::claim_log_and_clear_rollback_info: fix rollback_info_trimmed_to

We have been setting it to the old head value.  This is usually
harmless since the new head will virtually always be ahead of the
old head for claim_log_and_clear_rollback_info, but can cause trouble
in some edge cases.

Fixes: #9481
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 0769310ccd4e0dceebd8ea601e8eb5c0928e0603)
Merge remote-tracking branch 'origin/wip-9339' into wip-sam-testing-firefly
ReplicatedPG::start_flush: remove superfluous loop

Signed-off-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 66c7439ea0888777b5cfc08bcb0fbd7bfd8653c3)
ReplicatedPG:start_flush send a second delete

Suppose we start with the following in the cache pool:

30:[29,21,20,15,10,4]:[22(21), 15(15,10), 4(4)]+head

The object doesn't exist at 29 or 20.

First, we flush 4 leaving the backing pool with:

3:[]+head

Then, we begin to flush 15 with a delete with snapc 4:[4] leaving the
backing pool with:

4:[4]:[4(4)]

Then, we finish flushing 15 with snapc 9:[4] with leaving the backing
pool with:

9:[4]:[4(4)]+head

Next, snaps 10 and 15 are removed causing clone 10 to be removed leaving
the cache with:

30:[29,21,20,4]:[22(21),4(4)]+head

We next begin to flush 22 by sending a delete with snapc 4(4) since
prev_snapc is 4 <---------- here is the bug

The backing pool ignores this request since 4 < 9 (ORDERSNAP) leaving it
with:

9:[4]:[4(4)]

Then, we complete flushing 22 with snapc 19:[4] leaving the backing pool
with:

19:[4]:[4(4)]+head

Then, we begin to flush head by deleting with snapc 22:[21,20,4] leaving
the backing pool with:

22[21,20,4]:[22(21,20), 4(4)]

Finally, we flush head leaving the backing pool with:

30:[29,21,20,4]:[22(21*,20*),4(4)]+head

When we go to flush clone 22, all we know is that 22 is dirty, has snaps
[21], and 4 is clean. As part of flushing 22, we need to do two things:
1) Ensure that the current head is cloned as cloneid 4 with snaps [4] by
sending a delete at snapc 4:[4].
2) Flush the data at snap sequence < 21 by sending a copyfrom with snapc
20:[20,4].

Unfortunately, it is possible that 1, 1&2, or 1 and part of the flush
process for some other now non-existent clone have already been
performed.  Because of that, between 1) and 2), we need to send
a second delete ensuring that the object does not exist at 20.

Fixes: #9054
Backport: firefly
Related: 66c7439ea0888777b5cfc08bcb0fbd7bfd8653c3
Signed-off-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 4843fd510b33a71999cdf9c2cfa2b4c318fa80fd)
PG: mark_log_for_rewrite on resurrection

Fixes: #8777
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 8346e10755027e982f26bab4642334fd91cc31aa)
PG: wait until we've build the missing set to discover_all_missing

Fixes: #9179
Backport: firefly
Signed-off-by: Samuel Just <sam.just@inktank.com>
(cherry picked from commit 970d9830a3a6e8568337c660fb8b4c4a60a2b3bf)

Conflicts:
	src/osd/PG.cc
Merge remote-tracking branch 'origin/wip-9240' into wip-sam-testing-firefly
Merge branch 'wip-sam-testing-firefly' into firefly