dm: eliminate 'split_discard_bios' flag from DM target interface

There is no need to have DM core split discards on behalf of a DM target
now that blk_queue_split() handles splitting discards based on the
queue_limits.  A DM target just needs to set max_discard_sectors,
discard_granularity, etc, in queue_limits.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-cache-target.c

@@ -2496,7 +2496,6 @@ static int cache_create(struct cache_args *ca, struct cache **result)
 
 	ti->num_discard_bios = 1;
 	ti->discards_supported = true;
-	ti->split_discard_bios = false;
 
 	ti->per_io_data_size = sizeof(struct per_bio_data);
 

drivers/md/dm-raid.c

@@ -2986,11 +2986,6 @@ static void configure_discard_support(struct raid_set *rs)
 		}
 	}
 
-	/*
-	 * RAID1 and RAID10 personalities require bio splitting,
-	 * RAID0/4/5/6 don't and process large discard bios properly.
-	 */
-	ti->split_discard_bios = !!(rs_is_raid1(rs) || rs_is_raid10(rs));
 	ti->num_discard_bios = 1;
 }
 
@@ -3747,6 +3742,15 @@ static void raid_io_hints(struct dm_target *ti, struct queue_limits *limits)
 
 	blk_limits_io_min(limits, chunk_size);
 	blk_limits_io_opt(limits, chunk_size * mddev_data_stripes(rs));
+
+	/*
+	 * RAID1 and RAID10 personalities require bio splitting,
+	 * RAID0/4/5/6 don't and process large discard bios properly.
+	 */
+	if (rs_is_raid1(rs) || rs_is_raid10(rs)) {
+		limits->discard_granularity = chunk_size;
+		limits->max_discard_sectors = chunk_size;
+	}
 }
 
 static void raid_postsuspend(struct dm_target *ti)

drivers/md/dm-thin.c

@@ -4227,7 +4227,6 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	if (tc->pool->pf.discard_enabled) {
 		ti->discards_supported = true;
 		ti->num_discard_bios = 1;
-		ti->split_discard_bios = false;
 	}
 
 	mutex_unlock(&dm_thin_pool_table.mutex);

drivers/md/dm-zoned-target.c

@@ -727,7 +727,6 @@ static int dmz_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	ti->per_io_data_size = sizeof(struct dmz_bioctx);
 	ti->flush_supported = true;
 	ti->discards_supported = true;
-	ti->split_discard_bios = true;
 
 	/* The exposed capacity is the number of chunks that can be mapped */
 	ti->len = (sector_t)dmz_nr_chunks(dmz->metadata) << dev->zone_nr_sectors_shift;

drivers/md/dm.c

@@ -1478,17 +1478,10 @@ static unsigned get_num_write_zeroes_bios(struct dm_target *ti)
 	return ti->num_write_zeroes_bios;
 }
 
-typedef bool (*is_split_required_fn)(struct dm_target *ti);
-
-static bool is_split_required_for_discard(struct dm_target *ti)
-{
-	return ti->split_discard_bios;
-}
-
 static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
-				       unsigned num_bios, bool is_split_required)
+				       unsigned num_bios)
 {
-	unsigned len;
+	unsigned len = ci->sector_count;
 
 	/*
 	 * Even though the device advertised support for this type of
@@ -1499,11 +1492,6 @@ static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *
 	if (!num_bios)
 		return -EOPNOTSUPP;
 
-	if (!is_split_required)
-		len = min((sector_t)ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
-	else
-		len = min((sector_t)ci->sector_count, max_io_len(ci->sector, ti));
-
 	__send_duplicate_bios(ci, ti, num_bios, &len);
 
 	ci->sector += len;
@@ -1514,23 +1502,22 @@ static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *
 
 static int __send_discard(struct clone_info *ci, struct dm_target *ti)
 {
-	return __send_changing_extent_only(ci, ti, get_num_discard_bios(ti),
-					   is_split_required_for_discard(ti));
+	return __send_changing_extent_only(ci, ti, get_num_discard_bios(ti));
 }
 
 static int __send_secure_erase(struct clone_info *ci, struct dm_target *ti)
 {
-	return __send_changing_extent_only(ci, ti, get_num_secure_erase_bios(ti), false);
+	return __send_changing_extent_only(ci, ti, get_num_secure_erase_bios(ti));
 }
 
 static int __send_write_same(struct clone_info *ci, struct dm_target *ti)
 {
-	return __send_changing_extent_only(ci, ti, get_num_write_same_bios(ti), false);
+	return __send_changing_extent_only(ci, ti, get_num_write_same_bios(ti));
 }
 
 static int __send_write_zeroes(struct clone_info *ci, struct dm_target *ti)
 {
-	return __send_changing_extent_only(ci, ti, get_num_write_zeroes_bios(ti), false);
+	return __send_changing_extent_only(ci, ti, get_num_write_zeroes_bios(ti));
 }
 
 static bool is_abnormal_io(struct bio *bio)

include/linux/device-mapper.h

@@ -315,12 +315,6 @@ struct dm_target {
 	 * whether or not its underlying devices have support.
 	 */
 	bool discards_supported:1;
-
-	/*
-	 * Set if the target required discard bios to be split
-	 * on max_io_len boundary.
-	 */
-	bool split_discard_bios:1;
 };
 
 /* Each target can link one of these into the table */

include/uapi/linux/dm-ioctl.h

@@ -270,9 +270,9 @@ enum {
 #define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR	4
-#define DM_VERSION_MINOR	39
+#define DM_VERSION_MINOR	40
 #define DM_VERSION_PATCHLEVEL	0
-#define DM_VERSION_EXTRA	"-ioctl (2018-04-03)"
+#define DM_VERSION_EXTRA	"-ioctl (2019-01-18)"
 
 /* Status bits */
 #define DM_READONLY_FLAG	(1 << 0) /* In/Out */