5 files changed, 105 insertions, 12 deletions

diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
index 9200dbf2391a..f043b5f433b2 100644
--- a/drivers/md/dm-linear.c
+++ b/drivers/md/dm-linear.c
@@ -53,6 +53,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         }
 
         ti->num_flush_requests = 1;
+        ti->num_discard_requests = 1;
         ti->private = lc;
         return 0;
 
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index bc60ef77a0d8..f9fc07d7a4b9 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -54,6 +54,8 @@ struct dm_table {
         sector_t *highs;
         struct dm_target *targets;
 
+        unsigned discards_supported:1;
+
         /*
          * Indicates the rw permissions for the new logical
          * device.  This should be a combination of FMODE_READ
@@ -203,6 +205,7 @@ int dm_table_create(struct dm_table **result, fmode_t mode,
 
         INIT_LIST_HEAD(&t->devices);
         atomic_set(&t->holders, 0);
+        t->discards_supported = 1;
 
         if (!num_targets)
                 num_targets = KEYS_PER_NODE;
@@ -770,6 +773,9 @@ int dm_table_add_target(struct dm_table *t, const char *type,
 
         t->highs[t->num_targets++] = tgt->begin + tgt->len - 1;
 
+        if (!tgt->num_discard_requests)
+                t->discards_supported = 0;
+
         return 0;
 
  bad:
@@ -1135,6 +1141,11 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
         else
                 queue_flag_set_unlocked(QUEUE_FLAG_CLUSTER, q);
 
+        if (!dm_table_supports_discards(t))
+                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
+        else
+                queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+
         dm_table_set_integrity(t);
 
         /*
@@ -1281,6 +1292,39 @@ struct mapped_device *dm_table_get_md(struct dm_table *t)
         return t->md;
 }
 
+static int device_discard_capable(struct dm_target *ti, struct dm_dev *dev,
+                                  sector_t start, sector_t len, void *data)
+{
+        struct request_queue *q = bdev_get_queue(dev->bdev);
+
+        return q && blk_queue_discard(q);
+}
+
+bool dm_table_supports_discards(struct dm_table *t)
+{
+        struct dm_target *ti;
+        unsigned i = 0;
+
+        if (!t->discards_supported)
+                return 0;
+
+        /*
+         * Ensure that at least one underlying device supports discards.
+         * t->devices includes internal dm devices such as mirror logs
+         * so we need to use iterate_devices here, which targets
+         * supporting discard must provide.
+         */
+        while (i < dm_table_get_num_targets(t)) {
+                ti = dm_table_get_target(t, i++);
+
+                if (ti->type->iterate_devices &&
+                    ti->type->iterate_devices(ti, device_discard_capable, NULL))
+                        return 1;
+        }
+
+        return 0;
+}
+
 EXPORT_SYMBOL(dm_vcalloc);
 EXPORT_SYMBOL(dm_get_device);
 EXPORT_SYMBOL(dm_put_device);
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);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 0d7b374c5dc2..0c2dd5f4af76 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -61,6 +61,7 @@ int dm_table_any_congested(struct dm_table *t, int bdi_bits);
 int dm_table_any_busy_target(struct dm_table *t);
 unsigned dm_table_get_type(struct dm_table *t);
 bool dm_table_request_based(struct dm_table *t);
+bool dm_table_supports_discards(struct dm_table *t);
 int dm_table_alloc_md_mempools(struct dm_table *t);
 void dm_table_free_md_mempools(struct dm_table *t);
 struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 531a6f2635ae..751ce21dea7b 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -180,6 +180,12 @@ struct dm_target {
          */
         unsigned num_flush_requests;
 
+        /*
+         * The number of discard requests that will be submitted to the
+         * target.  map_info->request_nr is used just like num_flush_requests.
+         */
+        unsigned num_discard_requests;
+
         /* target specific data */
         void *private;