1 files changed, 18 insertions, 5 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index b5b9118c0636..5e553c50c215 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1467,7 +1467,19 @@ static int snapshot_iterate_devices(struct dm_target *ti,
 /*-----------------------------------------------------------------
  * Origin methods
  *---------------------------------------------------------------*/
-static int __origin_write(struct list_head *snapshots, struct bio *bio)
+
+/*
+ * If no exceptions need creating, DM_MAPIO_REMAPPED is returned and any
+ * supplied bio was ignored.  The caller may submit it immediately.
+ * (No remapping actually occurs as the origin is always a direct linear
+ * map.)
+ *
+ * If further exceptions are required, DM_MAPIO_SUBMITTED is returned
+ * and any supplied bio is added to a list to be submitted once all
+ * the necessary exceptions exist.
+ */
+static int __origin_write(struct list_head *snapshots, sector_t sector,
+                          struct bio *bio)
 {
         int r = DM_MAPIO_REMAPPED, first = 0;
         struct dm_snapshot *snap;
@@ -1486,14 +1498,14 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                         goto next_snapshot;
 
                 /* Nothing to do if writing beyond end of snapshot */
-                if (bio->bi_sector >= dm_table_get_size(snap->ti->table))
+                if (sector >= dm_table_get_size(snap->ti->table))
                         goto next_snapshot;
 
                 /*
                  * Remember, different snapshots can have
                  * different chunk sizes.
                  */
-                chunk = sector_to_chunk(snap->store, bio->bi_sector);
+                chunk = sector_to_chunk(snap->store, sector);
 
                 /*
                  * Check exception table to see if block
@@ -1543,7 +1555,8 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                                 first = 1;
                         }
 
-                        bio_list_add(&primary_pe->origin_bios, bio);
+                        if (bio)
+                                bio_list_add(&primary_pe->origin_bios, bio);
 
                         r = DM_MAPIO_SUBMITTED;
                 }
@@ -1599,7 +1612,7 @@ static int do_origin(struct dm_dev *origin, struct bio *bio)
         down_read(&_origins_lock);
         o = __lookup_origin(origin->bdev);
         if (o)
-                r = __origin_write(&o->snapshots, bio);
+                r = __origin_write(&o->snapshots, bio->bi_sector, bio);
         up_read(&_origins_lock);
 
         return r;