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dm: introduce num_flush_requests 

Introduce num_flush_requests for a target to set to say how many flush
instructions (empty barriers) it wants to receive.  These are sent by
__clone_and_map_empty_barrier with map_info->flush_request going from 0
to (num_flush_requests - 1).

Old targets without flush support won't receive any flush requests.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2009-06-22 10:12:20 +01:00 committed by Alasdair G Kergon
parent 27eaa14975
commit f9ab94cee3
2 changed files with 50 additions and 0 deletions
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39
drivers/md/dm.c
View File

@ -750,6 +750,40 @@ static struct bio *clone_bio(struct bio *bio, sector_t sector,
return clone;
}
static void __flush_target(struct clone_info *ci, struct dm_target *ti,
unsigned flush_nr)
{
struct dm_target_io *tio = alloc_tio(ci->md);
struct bio *clone;
tio->io = ci->io;
tio->ti = ti;
memset(&tio->info, 0, sizeof(tio->info));
tio->info.flush_request = flush_nr;
clone = bio_alloc_bioset(GFP_NOIO, 0, ci->md->bs);
__bio_clone(clone, ci->bio);
clone->bi_destructor = dm_bio_destructor;
__map_bio(ti, clone, tio);
}
static int __clone_and_map_empty_barrier(struct clone_info *ci)
{
unsigned target_nr = 0, flush_nr;
struct dm_target *ti;
while ((ti = dm_table_get_target(ci->map, target_nr++)))
for (flush_nr = 0; flush_nr < ti->num_flush_requests;
flush_nr++)
__flush_target(ci, ti, flush_nr);
ci->sector_count = 0;
return 0;
}
static int __clone_and_map(struct clone_info *ci)
{
struct bio *clone, *bio = ci->bio;
@ -757,6 +791,9 @@ static int __clone_and_map(struct clone_info *ci)
sector_t len = 0, max;
struct dm_target_io *tio;
if (unlikely(bio_empty_barrier(bio)))
return __clone_and_map_empty_barrier(ci);
ti = dm_table_find_target(ci->map, ci->sector);
if (!dm_target_is_valid(ti))
return -EIO;
@ -877,6 +914,8 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
ci.io->md = md;
ci.sector = bio->bi_sector;
ci.sector_count = bio_sectors(bio);
if (unlikely(bio_empty_barrier(bio)))
ci.sector_count = 1;
ci.idx = bio->bi_idx;
start_io_acct(ci.io);

11
include/linux/device-mapper.h
View File

@ -21,6 +21,7 @@ typedef enum { STATUSTYPE_INFO, STATUSTYPE_TABLE } status_type_t;
union map_info {
void *ptr;
unsigned long long ll;
unsigned flush_request;
};
/*
@ -167,6 +168,16 @@ struct dm_target {
/* Always a power of 2 */
sector_t split_io;
/*
* A number of zero-length barrier requests that will be submitted
* to the target for the purpose of flushing cache.
*
* The request number will be placed in union map_info->flush_request.
* It is a responsibility of the target driver to remap these requests
* to the real underlying devices.
*/
unsigned num_flush_requests;
/*
* These are automatically filled in by
* dm_table_get_device.