[dm-devel] [PATCH 7/17] bottom-layer barrier support (fwd)

[Mikulas Patocka]

dm-__clone_and_map_empty_barrier.patch

Introduce __clone_and_map_empty_barrier that will pass empty barrier
to the targets. Each target receives as many requests as it set up
in num_flush_requests.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>

---
 drivers/md/dm.c |   32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

Index: linux-2.6.30-rc2-devel/drivers/md/dm.c
===================================================================
--- linux-2.6.30-rc2-devel.orig/drivers/md/dm.c	2009-04-15 16:35:46.000000000 +0200
+++ linux-2.6.30-rc2-devel/drivers/md/dm.c	2009-04-15 16:35:49.000000000 +0200
@@ -761,6 +761,8 @@ static struct bio *clone_bio(struct bio 
 	return clone;
 }
 
+static int __clone_and_map_empty_barrier(struct clone_info *ci);
+
 static int __clone_and_map(struct clone_info *ci)
 {
 	struct bio *clone, *bio = ci->bio;
@@ -768,6 +770,9 @@ static int __clone_and_map(struct clone_
 	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;
@@ -861,6 +866,31 @@ static int __clone_and_map(struct clone_
 	return 0;
 }
 
+static int __clone_and_map_empty_barrier(struct clone_info *ci)
+{
+	unsigned i, j, n;
+	n = dm_table_get_num_targets(ci->map);
+	for (i = 0; i < n; i++) {
+		struct bio *clone;
+		struct dm_target *ti = dm_table_get_target(ci->map, i);
+		for (j = 0; j < ti->num_flush_requests; j++) {
+			struct dm_target_io *tio = alloc_tio(ci->md);
+			tio->io = ci->io;
+			tio->ti = ti;
+			memset(&tio->info, 0, sizeof(tio->info));
+			tio->info.flush_request = j;
+
+			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);
+		}
+	}
+	ci->sector_count = 0;
+	return 0;
+}
+
 /*
  * Split the bio into several clones and submit it to targets.
  */
@@ -888,6 +918,8 @@ static void __split_and_process_bio(stru
 	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);