Commit 00065f92 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm zero: add discard support 



Add zero_io_hints() and set discard limits so that the zero target
advertises support for discards.

The zero target will ignore discards.

This is useful when the user combines dm-zero with other
discard-supporting targets in the same table; without dm-zero support,
discards would be disabled for the whole combined device.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Tested-by: default avatarMilan Broz <gmazyland@gmail.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 85c938e8

drivers/md/dm-zero.c

+11 −1
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv) 
	 * Silently drop discards, avoiding -EOPNOTSUPP.

	 */

	ti->num_discard_bios = 1;

	ti->discards_supported = true;



	return 0;

}
@@ -45,6 +46,7 @@ static int zero_map(struct dm_target *ti, struct bio *bio) 
		zero_fill_bio(bio);

		break;

	case REQ_OP_WRITE:

	case REQ_OP_DISCARD:

		/* writes get silently dropped */

		break;

	default:
@@ -57,13 +59,21 @@ static int zero_map(struct dm_target *ti, struct bio *bio) 
	return DM_MAPIO_SUBMITTED;

}



static void zero_io_hints(struct dm_target *ti, struct queue_limits *limits)

{

	limits->max_discard_sectors = UINT_MAX;

	limits->max_hw_discard_sectors = UINT_MAX;

	limits->discard_granularity = 512;

}



static struct target_type zero_target = {

	.name   = "zero",

	.version = {1, 1, 0},

	.version = {1, 2, 0},

	.features = DM_TARGET_NOWAIT,

	.module = THIS_MODULE,

	.ctr    = zero_ctr,

	.map    = zero_map,

	.io_hints = zero_io_hints,

};



static int __init dm_zero_init(void)