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authorAlasdair G Kergon <agk@redhat.com>2013-03-01 22:45:49 +0000
committerAlasdair G Kergon <agk@redhat.com>2013-03-01 22:45:49 +0000
commitb0d8ed4d96a26ef3ac54a4aa8911c9413070662e (patch)
treeb43cc88d671e85840a625cdb0de75754182043ac /drivers/md
parentdf5d2e9089c7d5b8c46f767e4278610ea3e815b9 (diff)
dm: add target num_write_bios fn
Add a num_write_bios function to struct target. If an instance of a target sets this, it will be queried before the target's mapping function is called on a write bio, and the response controls the number of copies of the write bio that the target will receive. This provides a convenient way for a target to send the same data to more than one device. The new cache target uses this in writethrough mode, to send the data both to the cache and the backing device. Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm.c22
1 files changed, 15 insertions, 7 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index e417cf0a69e..7e469260fe5 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1152,15 +1152,23 @@ static void __clone_and_map_data_bio(struct clone_info *ci, struct dm_target *ti
{
struct bio *bio = ci->bio;
struct dm_target_io *tio;
+ unsigned target_bio_nr;
+ unsigned num_target_bios = 1;
- tio = alloc_tio(ci, ti, nr_iovecs, 0);
-
- if (split_bvec)
- clone_split_bio(tio, bio, sector, idx, offset, len);
- else
- clone_bio(tio, bio, sector, idx, bv_count, len);
+ /*
+ * Does the target want to receive duplicate copies of the bio?
+ */
+ if (bio_data_dir(bio) == WRITE && ti->num_write_bios)
+ num_target_bios = ti->num_write_bios(ti, bio);
- __map_bio(tio);
+ for (target_bio_nr = 0; target_bio_nr < num_target_bios; target_bio_nr++) {
+ tio = alloc_tio(ci, ti, nr_iovecs, target_bio_nr);
+ if (split_bvec)
+ clone_split_bio(tio, bio, sector, idx, offset, len);
+ else
+ clone_bio(tio, bio, sector, idx, bv_count, len);
+ __map_bio(tio);
+ }
}
typedef unsigned (*get_num_bios_fn)(struct dm_target *ti);