dm log: fix unitialized bio operation flags

Commit e604714 ("dm: use bio op accessors") switched DM over to
using bio_set_op_attrs() but didn't take care to initialize
lc->io_req.bi_op_flags in dm-log.c:rw_header().  This caused
rw_header()'s call to dm_io() to make bio->bi_op_flags be uninitialized
in dm-io.c:do_region(), which ultimately resulted in a SCSI BUG() in
sd_init_command().

Also, adjust rw_header() and its callers to use REQ_OP_{READ|WRITE}.

Fixes: e604714 ("dm: use bio op accessors")
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@seagate.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-log.c

@@ -291,9 +291,10 @@ static void header_from_disk(struct log_header_core *core, struct log_header_dis
 	core->nr_regions = le64_to_cpu(disk->nr_regions);
 }
 
-static int rw_header(struct log_c *lc, int rw)
+static int rw_header(struct log_c *lc, int op)
 {
-	lc->io_req.bi_op = rw;
+	lc->io_req.bi_op = op;
+	lc->io_req.bi_op_flags = 0;
 
 	return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
 }
@@ -316,7 +317,7 @@ static int read_header(struct log_c *log)
 {
 	int r;
 
-	r = rw_header(log, READ);
+	r = rw_header(log, REQ_OP_READ);
 	if (r)
 		return r;
 
@@ -630,7 +631,7 @@ static int disk_resume(struct dm_dirty_log *log)
 	header_to_disk(&lc->header, lc->disk_header);
 
 	/* write the new header */
-	r = rw_header(lc, WRITE);
+	r = rw_header(lc, REQ_OP_WRITE);
 	if (!r) {
 		r = flush_header(lc);
 		if (r)
@@ -698,7 +699,7 @@ static int disk_flush(struct dm_dirty_log *log)
 			log_clear_bit(lc, lc->clean_bits, i);
 	}
 
-	r = rw_header(lc, WRITE);
+	r = rw_header(lc, REQ_OP_WRITE);
 	if (r)
 		fail_log_device(lc);
 	else {