From: Mike Snitzer 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 Signed-off-by: Alasdair G Kergon --- drivers/md/dm-table.c | 15 +++++++-------- drivers/md/dm.c | 3 ++- 2 files changed, 9 insertions(+), 9 deletions(-) Index: linux/drivers/md/dm-table.c =================================================================== --- linux.orig/drivers/md/dm-table.c +++ linux/drivers/md/dm-table.c @@ -54,7 +54,6 @@ struct dm_table { sector_t *highs; struct dm_target *targets; - unsigned discards_supported:1; unsigned integrity_supported:1; /* @@ -209,7 +208,6 @@ int dm_table_create(struct dm_table **re 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 @@ int dm_table_add_target(struct dm_table 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 @@ bool dm_table_supports_discards(struct d 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; Index: linux/drivers/md/dm.c =================================================================== --- linux.orig/drivers/md/dm.c +++ linux/drivers/md/dm.c @@ -1179,7 +1179,8 @@ static int __clone_and_map_discard(struc /* * 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)