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>

7 files changed, 17 insertions, 35 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index b29a8327eed1..adc529f12b6b 100644
--- a/drivers/md/dm-cache-target.c
+++ b/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);
 
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index adcfe8ae10aa..9fdef6897316 100644
--- a/drivers/md/dm-raid.c
+++ b/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)
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index e83b63608262..0d9ded0f5e50 100644
--- a/drivers/md/dm-thin.c
+++ b/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);
diff --git a/drivers/md/dm-zoned-target.c b/drivers/md/dm-zoned-target.c
index 6af5babe6837..8865c1709e16 100644
--- a/drivers/md/dm-zoned-target.c
+++ b/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;
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7a774fcd0194..55f12df3589d 100644
--- a/drivers/md/dm.c
+++ b/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)
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index e528baebad69..0f5b3d7c6cb3 100644
--- a/include/linux/device-mapper.h
+++ b/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 */
diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index d1e49514977b..f396a82dfd3e 100644
--- a/include/uapi/linux/dm-ioctl.h
+++ b/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 */