3 files changed, 22 insertions, 4 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index b42e71bb9e67..d8544e1a4c1f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -482,9 +482,13 @@ static int clone_endio(struct bio *bio, unsigned int done, int error)
                 r = endio(tio->ti, bio, error, &tio->info);
                 if (r < 0)
                         error = r;
-                else if (r > 0)
-                        /* the target wants another shot at the io */
+                else if (r == DM_ENDIO_INCOMPLETE)
+                        /* The target will handle the io */
                         return 1;
+                else if (r) {
+                        DMWARN("unimplemented target endio return value: %d", r);
+                        BUG();
+                }
         }
 
         dec_pending(tio->io, error);
@@ -542,7 +546,7 @@ static void __map_bio(struct dm_target *ti, struct bio *clone,
         atomic_inc(&tio->io->io_count);
         sector = clone->bi_sector;
         r = ti->type->map(ti, clone, &tio->info);
-        if (r > 0) {
+        if (r == DM_MAPIO_REMAPPED) {
                 /* the bio has been remapped so dispatch it */
 
                 blk_add_trace_remap(bdev_get_queue(clone->bi_bdev), clone,
@@ -560,6 +564,9 @@ static void __map_bio(struct dm_target *ti, struct bio *clone,
                 clone->bi_private = md->bs;
                 bio_put(clone);
                 free_tio(md, tio);
+        } else if (r) {
+                DMWARN("unimplemented target map return value: %d", r);
+                BUG();
         }
 }
 
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 81c98d6e35e9..293d5ce62a21 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -33,6 +33,17 @@
 #define SECTOR_SHIFT 9
 
 /*
+ * Definitions of return values from target end_io function.
+ */
+#define DM_ENDIO_INCOMPLETE     1
+
+/*
+ * Definitions of return values from target map function.
+ */
+#define DM_MAPIO_SUBMITTED      0
+#define DM_MAPIO_REMAPPED       1
+
+/*
  * Suspend feature flags
  */
 #define DM_SUSPEND_LOCKFS_FLAG          (1 << 0)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 9194ff2d08c0..2e5c42346c38 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -39,7 +39,7 @@ typedef void (*dm_dtr_fn) (struct dm_target *ti);
  * The map function must return:
  * < 0: error
  * = 0: The target will handle the io by resubmitting it later
- * > 0: simple remap complete
+ * = 1: simple remap complete
  */
 typedef int (*dm_map_fn) (struct dm_target *ti, struct bio *bio,
                           union map_info *map_context);