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>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7d9ca70..badb751 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -750,6 +750,40 @@
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 @@
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 @@
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);