Commit 936688d7 authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon
Browse files

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: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 283a8328

drivers/md/dm-table.c

+7 −8
Original line number Diff line number Diff line
@@ -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 **result, fmode_t mode, 
	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, const char *type, 


	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 dm_table *t) 
	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;

drivers/md/dm.c

+2 −1
Original line number Diff line number Diff line
@@ -1179,7 +1179,8 @@ static int __clone_and_map_discard(struct clone_info *ci) 


		/*

		 * 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)

CRA Git | Maintained and supported by SUSTech CRA and CCSE