dm: remove unused 'num_write_bios' target interface

No DM target provides num_write_bios and none has since dm-cache's
brief use in 2013.

Having the possibility of num_write_bios > 1 complicates bio
allocation.  So remove the interface and assume there is only one bio
needed.

If a target ever needs more, it must provide a suitable bioset and
allocate itself based on its particular needs.

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

1 files changed, 0 insertions, 15 deletions

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index a5538433c927..5a68b366e664 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -221,14 +221,6 @@ struct target_type {
 #define dm_target_is_wildcard(type)     ((type)->features & DM_TARGET_WILDCARD)
 
 /*
- * Some targets need to be sent the same WRITE bio severals times so
- * that they can send copies of it to different devices.  This function
- * examines any supplied bio and returns the number of copies of it the
- * target requires.
- */
-typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio);
-
-/*
  * A target implements own bio data integrity.
  */
 #define DM_TARGET_INTEGRITY             0x00000010
@@ -291,13 +283,6 @@ struct dm_target {
          */
         unsigned per_io_data_size;
 
-        /*
-         * If defined, this function is called to find out how many
-         * duplicate bios should be sent to the target when writing
-         * data.
-         */
-        dm_num_write_bios_fn num_write_bios;
-
         /* target specific data */
         void *private;