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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 <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 9c5091f2

drivers/md/dm-table.c

+29 −1
Original line number Diff line number Diff line
@@ -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)

{
@@ -1445,6 +1472,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q, 
	else

		queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);



	if (!dm_table_supports_write_same(t))

		q->limits.max_write_same_sectors = 0;



	dm_table_set_integrity(t);

include/linux/device-mapper.h

+5 −0
Original line number Diff line number Diff line
@@ -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;