dm cache: fix problematic dual use of a single migration count variable
Introduce a new variable to count the number of allocated migration
structures. The existing variable cache->nr_migrations became
overloaded. It was used to:
i) track of the number of migrations in flight for the purposes of
quiescing during suspend.
ii) to estimate the amount of background IO occuring.
Recent discard changes meant that REQ_DISCARD bios are processed with
a migration. Discards are not background IO so nr_migrations was not
incremented. However this could cause quiescing to complete early.
(i) is now handled with a new variable cache->nr_allocated_migrations.
cache->nr_migrations has been renamed cache->nr_io_migrations.
cleanup_migration() is now called free_io_migration(), since it
decrements that variable.
Also, remove the unused cache->next_migration variable that got replaced
with with prealloc_structs a while ago.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org
1 file changed
