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-table.c b/drivers/md/dm-table.c
index bfe9c23..3909fa2 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -54,7 +54,6 @@
sector_t *highs;
struct dm_target *targets;
- unsigned discards_supported:1;
unsigned integrity_supported:1;
/*
@@ -209,7 +208,6 @@
INIT_LIST_HEAD(&t->devices);
INIT_LIST_HEAD(&t->target_callbacks);
atomic_set(&t->holders, 0);
- t->discards_supported = 1;
if (!num_targets)
num_targets = KEYS_PER_NODE;
@@ -791,8 +789,9 @@
t->highs[t->num_targets++] = tgt->begin + tgt->len - 1;
- if (!tgt->num_discard_requests)
- t->discards_supported = 0;
+ if (!tgt->num_discard_requests && tgt->discards_supported)
+ DMWARN("%s: %s: ignoring discards_supported because num_discard_requests is zero.",
+ dm_device_name(t->md), type);
return 0;
@@ -1359,19 +1358,19 @@
struct dm_target *ti;
unsigned i = 0;
- if (!t->discards_supported)
- return 0;
-
/*
* Unless any target used by the table set discards_supported,
* require at least one underlying device to support discards.
* t->devices includes internal dm devices such as mirror logs
* so we need to use iterate_devices here, which targets
- * supporting discard must provide.
+ * supporting discard selectively must provide.
*/
while (i < dm_table_get_num_targets(t)) {
ti = dm_table_get_target(t, i++);
+ if (!ti->num_discard_requests)
+ continue;
+
if (ti->discards_supported)
return 1;
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)