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Commit 23508a96 authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon
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dm: add WRITE SAME support 



WRITE SAME bios have a payload that contain a single page.  When
cloning WRITE SAME bios DM has no need to modify the bi_io_vec
attributes (and doing so would be detrimental).  DM need only alter the
start and end of the WRITE SAME bio accordingly.

Rather than duplicate __clone_and_map_discard, factor out a common
function that is also used by __clone_and_map_write_same.

Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent d54eaa5a

drivers/md/dm.c

+39 −5
Original line number Diff line number Diff line
@@ -1174,7 +1174,28 @@ static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti) 
	ci->sector_count = 0;

}



static int __clone_and_map_discard(struct clone_info *ci)

typedef unsigned (*get_num_requests_fn)(struct dm_target *ti);



static unsigned get_num_discard_requests(struct dm_target *ti)

{

	return ti->num_discard_requests;

}



static unsigned get_num_write_same_requests(struct dm_target *ti)

{

	return ti->num_write_same_requests;

}



typedef bool (*is_split_required_fn)(struct dm_target *ti);



static bool is_split_required_for_discard(struct dm_target *ti)

{

	return ti->split_discard_requests;

}



static int __clone_and_map_changing_extent_only(struct clone_info *ci,

						get_num_requests_fn get_num_requests,

						is_split_required_fn is_split_required)

{

	struct dm_target *ti;

	sector_t len;
@@ -1185,15 +1206,15 @@ static int __clone_and_map_discard(struct clone_info *ci) 
			return -EIO;



		/*

		 * Even though the device advertised discard support,

		 * that does not mean every target supports it, and

		 * Even though the device advertised support for this type of

		 * request, that does not mean every target supports it, and

		 * reconfiguration might also have changed that since the

		 * check was performed.

		 */

		if (!ti->num_discard_requests)

		if (!get_num_requests || !get_num_requests(ti))

			return -EOPNOTSUPP;



		if (!ti->split_discard_requests)

		if (is_split_required && !is_split_required(ti))

			len = min(ci->sector_count, max_io_len_target_boundary(ci->sector, ti));

		else

			len = min(ci->sector_count, max_io_len(ci->sector, ti));
@@ -1206,6 +1227,17 @@ static int __clone_and_map_discard(struct clone_info *ci) 
	return 0;

}



static int __clone_and_map_discard(struct clone_info *ci)

{

	return __clone_and_map_changing_extent_only(ci, get_num_discard_requests,

						    is_split_required_for_discard);

}



static int __clone_and_map_write_same(struct clone_info *ci)

{

	return __clone_and_map_changing_extent_only(ci, get_num_write_same_requests, NULL);

}



static int __clone_and_map(struct clone_info *ci)

{

	struct bio *bio = ci->bio;
@@ -1215,6 +1247,8 @@ static int __clone_and_map(struct clone_info *ci) 


	if (unlikely(bio->bi_rw & REQ_DISCARD))

		return __clone_and_map_discard(ci);

	else if (unlikely(bio->bi_rw & REQ_WRITE_SAME))

		return __clone_and_map_write_same(ci);



	ti = dm_table_find_target(ci->map, ci->sector);

	if (!dm_target_is_valid(ti))