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dm: prepare to support WRITE SAME

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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: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mike Snitzer 2012-12-21 20:23:36 +00:00 committed by Alasdair G Kergon
parent 9c5091f2ee
commit d54eaa5a0f
2 changed files with 34 additions and 1 deletions
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30
drivers/md/dm-table.c
View File

@ -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,
else
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;
dm_table_set_integrity(t);

5
include/linux/device-mapper.h
View File

@ -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;