merge_read_item() fails to update found->seq when combining delta items
from multiple finalized log trees. Add a test case to replicate the
conditions of this issue.
Each of 5 mounts sets totl value 1 on 2500 shared keys, giving an
expected total of 5 per key. Any total > 5 proves double-counting
from a stale seq.
The log_merge_force_partial trigger forces many partial merges per
cycle, creating the conditions where stale-seq items get spliced into
fs_root while finalized logs still exist. Parallel readers on all
mounts race against this window to detect double-counted values.
Signed-off-by: Auke Kok <auke.kok@versity.com>
e91feb18a3