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@xxxxxxxxxx>
---
drivers/md/dm-io.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
Index: linux-2.6.30-rc2-devel/drivers/md/dm-io.c
===================================================================
--- linux-2.6.30-rc2-devel.orig/drivers/md/dm-io.c 2009-04-24 09:24:26.000000000 +0200
+++ linux-2.6.30-rc2-devel/drivers/md/dm-io.c 2009-04-24 09:27:07.000000000 +0200
@@ -285,8 +285,12 @@ static void do_region(int rw, unsigned r
unsigned offset;
unsigned num_bvecs;
sector_t remaining = where->count;
+ /*
+ * "count" may be zero when "rw" indicates a write barrier request.
+ * In this case, we must send a zero-sized barrier.
+ */
- while (remaining) {
+ do {
/*
* Allocate a suitably sized-bio: we add an extra
* bvec for bio_get/set_region() and decrement bi_max_vecs
@@ -323,7 +327,7 @@ static void do_region(int rw, unsigned r
atomic_inc(&io->count);
submit_bio(rw, bio);
- }
+ } while (remaining);
}
static void dispatch_io(int rw, unsigned int num_regions,
@@ -342,7 +346,7 @@ static void dispatch_io(int rw, unsigned
*/
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);
}
--
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