1 files changed, 53 insertions, 12 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 0d4710175885..44aba29154fc 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1212,6 +1212,53 @@ static int __clone_and_map_empty_barrier(struct clone_info *ci)
         return 0;
 }
 
+/*
+ * Perform all io with a single clone.
+ */
+static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti)
+{
+        struct bio *clone, *bio = ci->bio;
+        struct dm_target_io *tio;
+
+        tio = alloc_tio(ci, ti);
+        clone = clone_bio(bio, ci->sector, ci->idx,
+                          bio->bi_vcnt - ci->idx, ci->sector_count,
+                          ci->md->bs);
+        __map_bio(ti, clone, tio);
+        ci->sector_count = 0;
+}
+
+static int __clone_and_map_discard(struct clone_info *ci)
+{
+        struct dm_target *ti;
+        sector_t max;
+
+        ti = dm_table_find_target(ci->map, ci->sector);
+        if (!dm_target_is_valid(ti))
+                return -EIO;
+
+        /*
+         * Even though the device advertised discard support,
+         * reconfiguration might have changed that since the
+         * check was performed.
+         */
+
+        if (!ti->num_discard_requests)
+                return -EOPNOTSUPP;
+
+        max = max_io_len(ci->md, ci->sector, ti);
+
+        if (ci->sector_count > max)
+                /*
+                 * FIXME: Handle a discard that spans two or more targets.
+                 */
+                return -EOPNOTSUPP;
+
+        __clone_and_map_simple(ci, ti);
+
+        return 0;
+}
+
 static int __clone_and_map(struct clone_info *ci)
 {
         struct bio *clone, *bio = ci->bio;
@@ -1222,27 +1269,21 @@ static int __clone_and_map(struct clone_info *ci)
         if (unlikely(bio_empty_barrier(bio)))
                 return __clone_and_map_empty_barrier(ci);
 
+        if (unlikely(bio->bi_rw & REQ_DISCARD))
+                return __clone_and_map_discard(ci);
+
         ti = dm_table_find_target(ci->map, ci->sector);
         if (!dm_target_is_valid(ti))
                 return -EIO;
 
         max = max_io_len(ci->md, ci->sector, ti);
 
-        /*
-         * Allocate a target io object.
-         */
-        tio = alloc_tio(ci, ti);
-
         if (ci->sector_count <= max) {
                 /*
                  * Optimise for the simple case where we can do all of
                  * the remaining io with a single clone.
                  */
-                clone = clone_bio(bio, ci->sector, ci->idx,
-                                  bio->bi_vcnt - ci->idx, ci->sector_count,
-                                  ci->md->bs);
-                __map_bio(ti, clone, tio);
-                ci->sector_count = 0;
+                __clone_and_map_simple(ci, ti);
 
         } else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
                 /*
@@ -1263,6 +1304,7 @@ static int __clone_and_map(struct clone_info *ci)
                         len += bv_len;
                 }
 
+                tio = alloc_tio(ci, ti);
                 clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len,
                                   ci->md->bs);
                 __map_bio(ti, clone, tio);
@@ -1286,12 +1328,11 @@ static int __clone_and_map(struct clone_info *ci)
                                         return -EIO;
 
                                 max = max_io_len(ci->md, ci->sector, ti);
-
-                                tio = alloc_tio(ci, ti);
                         }
 
                         len = min(remaining, max);
 
+                        tio = alloc_tio(ci, ti);
                         clone = split_bvec(bio, ci->sector, ci->idx,
                                            bv->bv_offset + offset, len,
                                            ci->md->bs);