Commit 1dd40c3e authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm: introduce dm_accept_partial_bio 



The function dm_accept_partial_bio allows the target to specify how many
sectors of the current bio it will process.  If the target only wants to
accept part of the bio, it calls dm_accept_partial_bio and the DM core
sends the rest of the data in next bio.

Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent e0d6609a

drivers/md/dm.c

+51 −8
Original line number Diff line number Diff line
@@ -1110,6 +1110,46 @@ int dm_set_target_max_io_len(struct dm_target *ti, sector_t len) 
}

EXPORT_SYMBOL_GPL(dm_set_target_max_io_len);



/*

 * A target may call dm_accept_partial_bio only from the map routine.  It is

 * allowed for all bio types except REQ_FLUSH.

 *

 * dm_accept_partial_bio informs the dm that the target only wants to process

 * additional n_sectors sectors of the bio and the rest of the data should be

 * sent in a next bio.

 *

 * A diagram that explains the arithmetics:

 * +--------------------+---------------+-------+

 * |         1          |       2       |   3   |

 * +--------------------+---------------+-------+

 *

 * <-------------- *tio->len_ptr --------------->

 *                      <------- bi_size ------->

 *                      <-- n_sectors -->

 *

 * Region 1 was already iterated over with bio_advance or similar function.

 *	(it may be empty if the target doesn't use bio_advance)

 * Region 2 is the remaining bio size that the target wants to process.

 *	(it may be empty if region 1 is non-empty, although there is no reason

 *	 to make it empty)

 * The target requires that region 3 is to be sent in the next bio.

 *

 * If the target wants to receive multiple copies of the bio (via num_*bios, etc),

 * the partially processed part (the sum of regions 1+2) must be the same for all

 * copies of the bio.

 */

void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors)

{

	struct dm_target_io *tio = container_of(bio, struct dm_target_io, clone);

	unsigned bi_size = bio->bi_iter.bi_size >> SECTOR_SHIFT;

	BUG_ON(bio->bi_rw & REQ_FLUSH);

	BUG_ON(bi_size > *tio->len_ptr);

	BUG_ON(n_sectors > bi_size);

	*tio->len_ptr -= bi_size - n_sectors;

	bio->bi_iter.bi_size = n_sectors << SECTOR_SHIFT;

}

EXPORT_SYMBOL_GPL(dm_accept_partial_bio);



static void __map_bio(struct dm_target_io *tio)

{

	int r;
@@ -1200,11 +1240,13 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci, 


static void __clone_and_map_simple_bio(struct clone_info *ci,

				       struct dm_target *ti,

				       unsigned target_bio_nr, unsigned len)

				       unsigned target_bio_nr, unsigned *len)

{

	struct dm_target_io *tio = alloc_tio(ci, ti, ci->bio->bi_max_vecs, target_bio_nr);

	struct bio *clone = &tio->clone;



	tio->len_ptr = len;



	/*

	 * Discard requests require the bio's inline iovecs be initialized.

	 * ci->bio->bi_max_vecs is BIO_INLINE_VECS anyway, for both flush
@@ -1212,13 +1254,13 @@ static void __clone_and_map_simple_bio(struct clone_info *ci, 
	 */

	 __bio_clone_fast(clone, ci->bio);

	if (len)

		bio_setup_sector(clone, ci->sector, len);

		bio_setup_sector(clone, ci->sector, *len);



	__map_bio(tio);

}



static void __send_duplicate_bios(struct clone_info *ci, struct dm_target *ti,

				  unsigned num_bios, unsigned len)

				  unsigned num_bios, unsigned *len)

{

	unsigned target_bio_nr;
@@ -1233,13 +1275,13 @@ static int __send_empty_flush(struct clone_info *ci) 


	BUG_ON(bio_has_data(ci->bio));

	while ((ti = dm_table_get_target(ci->map, target_nr++)))

		__send_duplicate_bios(ci, ti, ti->num_flush_bios, 0);

		__send_duplicate_bios(ci, ti, ti->num_flush_bios, NULL);



	return 0;

}



static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti,

				     sector_t sector, unsigned len)

				     sector_t sector, unsigned *len)

{

	struct bio *bio = ci->bio;

	struct dm_target_io *tio;
@@ -1254,7 +1296,8 @@ static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti 


	for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {

		tio = alloc_tio(ci, ti, 0, target_bio_nr);

		clone_bio(tio, bio, sector, len);

		tio->len_ptr = len;

		clone_bio(tio, bio, sector, *len);

		__map_bio(tio);

	}

}
@@ -1306,7 +1349,7 @@ static int __send_changing_extent_only(struct clone_info *ci, 
		else

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



		__send_duplicate_bios(ci, ti, num_bios, len);

		__send_duplicate_bios(ci, ti, num_bios, &len);



		ci->sector += len;

	} while (ci->sector_count -= len);
@@ -1345,7 +1388,7 @@ static int __split_and_process_non_flush(struct clone_info *ci) 


	len = min_t(sector_t, max_io_len(ci->sector, ti), ci->sector_count);



	__clone_and_map_data_bio(ci, ti, ci->sector, len);

	__clone_and_map_data_bio(ci, ti, ci->sector, &len);



	ci->sector += len;

	ci->sector_count -= len;

include/linux/device-mapper.h

+2 −0
Original line number Diff line number Diff line
@@ -291,6 +291,7 @@ struct dm_target_io { 
	struct dm_io *io;

	struct dm_target *ti;

	unsigned target_bio_nr;

	unsigned *len_ptr;

	struct bio clone;

};
@@ -401,6 +402,7 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid); 
struct gendisk *dm_disk(struct mapped_device *md);

int dm_suspended(struct dm_target *ti);

int dm_noflush_suspending(struct dm_target *ti);

void dm_accept_partial_bio(struct bio *bio, unsigned n_sectors);

union map_info *dm_get_rq_mapinfo(struct request *rq);



struct queue_limits *dm_get_queue_limits(struct mapped_device *md);

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