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authorMike Snitzer <snitzer@redhat.com>2010-08-12 04:14:08 +0100
committerAlasdair G Kergon <agk@redhat.com>2010-08-12 04:14:08 +0100
commit5ae89a8720c28caf35c4e53711d77df2856c404e (patch)
tree712ddc158309d7ad77e3c19e70f0ae9fafb94446 /drivers/md/dm-table.c
parent5ebaee6d290279d1df6ce45d6d54de8cfc473273 (diff)
downloadop-kernel-dev-5ae89a8720c28caf35c4e53711d77df2856c404e.zip
op-kernel-dev-5ae89a8720c28caf35c4e53711d77df2856c404e.tar.gz
dm: linear support discard
Allow discards to be passed through to linear mappings if at least one underlying device supports it. Discards will be forwarded only to devices that support them. A target that supports discards should set num_discard_requests to indicate how many times each discard request must be submitted to it. Verify table's underlying devices support discards prior to setting the associated DM device as capable of discards (via QUEUE_FLAG_DISCARD). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Reviewed-by: Joe Thornber <thornber@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-table.c')
-rw-r--r--drivers/md/dm-table.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index bc60ef7..f9fc07d 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -54,6 +54,8 @@ struct dm_table {
sector_t *highs;
struct dm_target *targets;
+ unsigned discards_supported:1;
+
/*
* Indicates the rw permissions for the new logical
* device. This should be a combination of FMODE_READ
@@ -203,6 +205,7 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
INIT_LIST_HEAD(&t->devices);
atomic_set(&t->holders, 0);
+ t->discards_supported = 1;
if (!num_targets)
num_targets = KEYS_PER_NODE;
@@ -770,6 +773,9 @@ 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;
+
return 0;
bad:
@@ -1135,6 +1141,11 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
else
queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);
+ if (!dm_table_supports_discards(t))
+ queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
+ else
+ queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+
dm_table_set_integrity(t);
/*
@@ -1281,6 +1292,39 @@ struct mapped_device *dm_table_get_md(struct dm_table *t)
return t->md;
}
+static int device_discard_capable(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ struct request_queue *q = bdev_get_queue(dev->bdev);
+
+ return q && blk_queue_discard(q);
+}
+
+bool dm_table_supports_discards(struct dm_table *t)
+{
+ struct dm_target *ti;
+ unsigned i = 0;
+
+ if (!t->discards_supported)
+ return 0;
+
+ /*
+ * Ensure that at least one underlying device supports 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.
+ */
+ while (i < dm_table_get_num_targets(t)) {
+ ti = dm_table_get_target(t, i++);
+
+ if (ti->type->iterate_devices &&
+ ti->type->iterate_devices(ti, device_discard_capable, NULL))
+ return 1;
+ }
+
+ return 0;
+}
+
EXPORT_SYMBOL(dm_vcalloc);
EXPORT_SYMBOL(dm_get_device);
EXPORT_SYMBOL(dm_put_device);
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