dm io: handle empty barriers
Accept empty barriers in dm-io.
dm-io will process empty write barrier requests just like the other
read/write requests.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index f6a714c..10f457c 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -309,7 +309,11 @@
unsigned num_bvecs;
sector_t remaining = where->count;
- while (remaining) {
+ /*
+ * where->count may be zero if rw holds a write barrier and we
+ * need to send a zero-sized barrier.
+ */
+ do {
/*
* Allocate a suitably sized-bio.
*/
@@ -339,7 +343,7 @@
atomic_inc(&io->count);
submit_bio(rw, bio);
- }
+ } while (remaining);
}
static void dispatch_io(int rw, unsigned int num_regions,
@@ -360,7 +364,7 @@
*/
for (i = 0; i < num_regions; i++) {
*dp = old_pages;
- if (where[i].count)
+ if (where[i].count || (rw & (1 << BIO_RW_BARRIER)))
do_region(rw, i, where + i, dp, io);
}