dm table: fix discard support
Remove 'discards_supported' from the dm_table structure. The same
information can be easily discovered from the table's target(s) in
dm_table_supports_discards().
Before this fix dm_table_supports_discards() would skip checking the
individual targets' 'discards_supported' flag if any one target in the
table didn't set num_discard_requests > 0. Now the per-target
'discards_supported' flag is effective at insuring the final DM device
advertises discard support. But, to be clear, targets that don't
support discards (!num_discard_requests) will not receive discard
requests.
Also DMWARN if a target sets 'discards_supported' override but forgets
to set 'num_discard_requests'.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 41abc6d..aeb0fa1 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1179,7 +1179,8 @@
/*
* Even though the device advertised discard support,
- * reconfiguration might have changed that since the
+ * that does not mean every target supports it, and
+ * reconfiguration might also have changed that since the
* check was performed.
*/
if (!ti->num_discard_requests)
