dm: fix __send_changing_extent_only() to send first bio and chain remainder

__send_changing_extent_only() must follow the same pattern that was
established with commit "dm: ensure bio submission follows a depth-first
tree walk".  That is: submit first bio up to split boundary and then
split the remainder to further submissions.

Suggested-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 9d255e5c968892091a41c9f3783bd368f7786efa..4e7682afebfa9be03f4ece3db7eb39e12da05e01 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1348,56 +1348,50 @@ 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,
+static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
                                       get_num_bios_fn get_num_bios,
                                       is_split_required_fn is_split_required)
 {
-       struct dm_target *ti;
        unsigned len;
        unsigned num_bios;
 
-       do {
-               ti = dm_table_find_target(ci->map, ci->sector);
-               if (!dm_target_is_valid(ti))
-                       return -EIO;
-
-               /*
-                * Even though the device advertised support for this type of
-                * request, that does not mean every target supports it, and
-                * reconfiguration might also have changed that since the
-                * check was performed.
-                */
-               num_bios = get_num_bios ? get_num_bios(ti) : 0;
-               if (!num_bios)
-                       return -EOPNOTSUPP;
+       /*
+        * Even though the device advertised support for this type of
+        * request, that does not mean every target supports it, and
+        * reconfiguration might also have changed that since the
+        * check was performed.
+        */
+       num_bios = get_num_bios ? get_num_bios(ti) : 0;
+       if (!num_bios)
+               return -EOPNOTSUPP;
 
-               if (is_split_required && !is_split_required(ti))
-                       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));
+       if (is_split_required && !is_split_required(ti))
+               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);
+       __send_duplicate_bios(ci, ti, num_bios, &len);
 
-               ci->sector += len;
-       } while (ci->sector_count -= len);
+       ci->sector += len;
+       ci->sector_count -= len;
 
        return 0;
 }
 
-static int __send_discard(struct clone_info *ci)
+static int __send_discard(struct clone_info *ci, struct dm_target *ti)
 {
-       return __send_changing_extent_only(ci, get_num_discard_bios,
+       return __send_changing_extent_only(ci, ti, get_num_discard_bios,
                                           is_split_required_for_discard);
 }
 
-static int __send_write_same(struct clone_info *ci)
+static int __send_write_same(struct clone_info *ci, struct dm_target *ti)
 {
-       return __send_changing_extent_only(ci, get_num_write_same_bios, NULL);
+       return __send_changing_extent_only(ci, ti, get_num_write_same_bios, NULL);
 }
 
-static int __send_write_zeroes(struct clone_info *ci)
+static int __send_write_zeroes(struct clone_info *ci, struct dm_target *ti)
 {
-       return __send_changing_extent_only(ci, get_num_write_zeroes_bios, NULL);
+       return __send_changing_extent_only(ci, ti, get_num_write_zeroes_bios, NULL);
 }
 
 /*
@@ -1410,17 +1404,17 @@ static int __split_and_process_non_flush(struct clone_info *ci)
        unsigned len;
        int r;
 
-       if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
-               return __send_discard(ci);
-       else if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
-               return __send_write_same(ci);
-       else if (unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES))
-               return __send_write_zeroes(ci);
-
        ti = dm_table_find_target(ci->map, ci->sector);
        if (!dm_target_is_valid(ti))
                return -EIO;
 
+       if (unlikely(bio_op(bio) == REQ_OP_DISCARD))
+               return __send_discard(ci, ti);
+       else if (unlikely(bio_op(bio) == REQ_OP_WRITE_SAME))
+               return __send_write_same(ci, ti);
+       else if (unlikely(bio_op(bio) == REQ_OP_WRITE_ZEROES))
+               return __send_write_zeroes(ci, ti);
+
        if (bio_op(bio) == REQ_OP_ZONE_REPORT)
                len = ci->sector_count;
        else