[dm-devel] [PATCH 8/17] bottom-layer barrier support

[Mikulas Patocka <mpatocka redhat com>]

dm-flush-make-empty-barrier.patch

Modify dm_flush so that is passes empty barrier flushes to the targets.

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

---
 drivers/md/dm.c |   10 ++++++++++
 1 file changed, 10 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 16:35:49.000000000 +0200
+++ linux-2.6.30-rc2-devel/drivers/md/dm.c	2009-04-15 16:35:54.000000000 +0200
@@ -175,6 +175,9 @@ struct mapped_device {
 
 	/* sysfs handle */
 	struct kobject kobj;
+
+	/* zero-length barrier that will be cloned and submitted to targets */
+	struct bio barrier_bio;
 };
 
 #define MIN_IOS 256
@@ -1475,6 +1478,13 @@ static int dm_wait_for_completion(struct
 static void dm_flush(struct mapped_device *md)
 {
 	dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
+
+	bio_init(&md->barrier_bio);
+	md->barrier_bio.bi_bdev = md->bdev;
+	md->barrier_bio.bi_rw = WRITE_BARRIER;
+	__split_and_process_bio(md, &md->barrier_bio);
+
+	dm_wait_for_completion(md, TASK_UNINTERRUPTIBLE);
 }
 
 static void process_barrier(struct mapped_device *md, struct bio *bio)