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dm: introduce dm_accept_partial_bio

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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: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2014-03-14 18:41:24 -04:00 committed by Mike Snitzer
parent e0d6609a5f
commit 1dd40c3ecd
2 changed files with 53 additions and 8 deletions
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59
drivers/md/dm.c
View File

@ -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;

2
include/linux/device-mapper.h
View File

@ -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);