Commit d54eaa5a authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon
Browse files

dm: prepare to support WRITE SAME

Allow targets to opt in to WRITE SAME support by setting
'num_write_same_requests' in the dm_target structure.

A dm device will only advertise WRITE SAME support if all its
targets and all its underlying devices support it.
Signed-off-by: default avatarMike Snitzer <>
Signed-off-by: default avatarAlasdair G Kergon <>
parent 9c5091f2
......@@ -1414,6 +1414,33 @@ static bool dm_table_all_devices_attribute(struct dm_table *t,
return 1;
static int device_not_write_same_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 && !q->limits.max_write_same_sectors;
static bool dm_table_supports_write_same(struct dm_table *t)
struct dm_target *ti;
unsigned i = 0;
while (i < dm_table_get_num_targets(t)) {
ti = dm_table_get_target(t, i++);
if (!ti->num_write_same_requests)
return false;
if (!ti->type->iterate_devices ||
!ti->type->iterate_devices(ti, device_not_write_same_capable, NULL))
return false;
return true;
void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
struct queue_limits *limits)
......@@ -1445,7 +1472,8 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
q->limits.max_write_same_sectors = 0;
if (!dm_table_supports_write_same(t))
q->limits.max_write_same_sectors = 0;
......@@ -205,6 +205,11 @@ struct dm_target {
unsigned num_discard_requests;
* The number of WRITE SAME requests that will be submitted to the target.
unsigned num_write_same_requests;
/* target specific data */
void *private;
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