1 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index d5f984b07466..1e483fa7afb4 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -175,6 +175,14 @@ struct target_type {
 #define DM_TARGET_IMMUTABLE             0x00000004
 #define dm_target_is_immutable(type)    ((type)->features & DM_TARGET_IMMUTABLE)
 
+/*
+ * 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);
+
 struct dm_target {
         struct dm_table *table;
         struct target_type *type;
@@ -214,6 +222,13 @@ struct dm_target {
          */
         unsigned per_bio_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;