1 files changed, 8 insertions, 3 deletions

diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index ed9c86cd053e..4789c42d9a3a 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -353,7 +353,7 @@ static int sync_io(struct dm_io_client *client, unsigned int num_regions,
 {
         struct io io;
 
-        if (num_regions > 1 && rw != WRITE) {
+        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
                 WARN_ON(1);
                 return -EIO;
         }
@@ -390,7 +390,7 @@ static int async_io(struct dm_io_client *client, unsigned int num_regions,
 {
         struct io *io;
 
-        if (num_regions > 1 && rw != WRITE) {
+        if (num_regions > 1 && (rw & RW_MASK) != WRITE) {
                 WARN_ON(1);
                 fn(1, context);
                 return -EIO;
@@ -436,7 +436,12 @@ static int dp_init(struct dm_io_request *io_req, struct dpages *dp)
 }
 
 /*
- * New collapsed (a)synchronous interface
+ * New collapsed (a)synchronous interface.
+ *
+ * If the IO is asynchronous (i.e. it has notify.fn), you must either unplug
+ * the queue with blk_unplug() some time later or set the BIO_RW_SYNC bit in
+ * io_req->bi_rw. If you fail to do one of these, the IO will be submitted to
+ * the disk after q->unplug_delay, which defaults to 3ms in blk-settings.c.
  */
 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
           struct dm_io_region *where, unsigned long *sync_error_bits)