dm: split discard requests on target boundaries

Update __clone_and_map_discard to loop across all targets in a DM
device's table when it processes a discard bio.  If a discard crosses a
target boundary it must be split accordingly.

Update __issue_target_requests and __issue_target_request to allow a
cloned discard bio to have a custom start sector and size.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 23 insertions, 24 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 561313a7dac2..ac384b2a6a33 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1193,7 +1193,7 @@ static struct dm_target_io *alloc_tio(struct clone_info *ci,
 }
 
 static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
-                                   unsigned request_nr)
+                                   unsigned request_nr, sector_t len)
 {
         struct dm_target_io *tio = alloc_tio(ci, ti);
         struct bio *clone;
@@ -1208,17 +1208,21 @@ static void __issue_target_request(struct clone_info *ci, struct dm_target *ti,
         clone = bio_alloc_bioset(GFP_NOIO, ci->bio->bi_max_vecs, ci->md->bs);
         __bio_clone(clone, ci->bio);
         clone->bi_destructor = dm_bio_destructor;
+        if (len) {
+                clone->bi_sector = ci->sector;
+                clone->bi_size = to_bytes(len);
+        }
 
         __map_bio(ti, clone, tio);
 }
 
 static void __issue_target_requests(struct clone_info *ci, struct dm_target *ti,
-                                    unsigned num_requests)
+                                    unsigned num_requests, sector_t len)
 {
         unsigned request_nr;
 
         for (request_nr = 0; request_nr < num_requests; request_nr++)
-                __issue_target_request(ci, ti, request_nr);
+                __issue_target_request(ci, ti, request_nr, len);
 }
 
 static int __clone_and_map_empty_barrier(struct clone_info *ci)
@@ -1227,7 +1231,7 @@ static int __clone_and_map_empty_barrier(struct clone_info *ci)
         struct dm_target *ti;
 
         while ((ti = dm_table_get_target(ci->map, target_nr++)))
-                __issue_target_requests(ci, ti, ti->num_flush_requests);
+                __issue_target_requests(ci, ti, ti->num_flush_requests, 0);
 
         ci->sector_count = 0;
 
@@ -1253,32 +1257,27 @@ static void __clone_and_map_simple(struct clone_info *ci, struct dm_target *ti)
 static int __clone_and_map_discard(struct clone_info *ci)
 {
         struct dm_target *ti;
-        sector_t max;
+        sector_t len;
 
-        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.
-         */
+        do {
+                ti = dm_table_find_target(ci->map, ci->sector);
+                if (!dm_target_is_valid(ti))
+                        return -EIO;
 
-        if (!ti->num_discard_requests)
-                return -EOPNOTSUPP;
-
-        max = max_io_len(ci->sector, ti);
-
-        if (ci->sector_count > max)
                 /*
-                 * FIXME: Handle a discard that spans two or more targets.
+                 * Even though the device advertised discard support,
+                 * reconfiguration might have changed that since the
+                 * check was performed.
                  */
-                return -EOPNOTSUPP;
+                if (!ti->num_discard_requests)
+                        return -EOPNOTSUPP;
 
-        __issue_target_requests(ci, ti, ti->num_discard_requests);
+                len = min(ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
 
-        ci->sector_count = 0;
+                __issue_target_requests(ci, ti, ti->num_discard_requests, len);
+
+                ci->sector += len;
+        } while (ci->sector_count -= len);
 
         return 0;
 }