From: Mikulas Patocka <mpatocka@redhat.com>
Date: Mon, 22 Jun 2009 09:12:21 +0000 (+0100)
Subject: dm: send empty barriers to targets in dm_flush
X-Git-Tag: v2.6.31-rc1~8^2~28
X-Git-Url: http://pileus.org/git/?a=commitdiff_plain;h=52b1fd5a27c625c78373e024bf570af3c9d44a79;p=~andy%2Flinux

dm: send empty barriers to targets in dm_flush

Pass empty barrier flushes to the targets in dm_flush().

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 edf9f246769..36142e947ff 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -164,6 +164,9 @@ 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
@@ -1477,6 +1480,13 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
 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)