---

yaml
---
r: 375255
b: refs/heads/master
c: 058ce5c
h: refs/heads/master
i:
  375253: 444a042
  375251: 6841ddf
  375247: eec122f
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 88a488f6243c98b38ac5191d4255e09d3b1c6455
+refs/heads/master: 058ce5ca8155a4c8eeac9b9e8a70e6664996337b

trunk/include/linux/device-mapper.h

@@ -79,11 +79,26 @@ typedef int (*dm_ioctl_fn) (struct dm_target *ti, unsigned int cmd,
 typedef int (*dm_merge_fn) (struct dm_target *ti, struct bvec_merge_data *bvm,
 			    struct bio_vec *biovec, int max_size);
 
+/*
+ * These iteration functions are typically used to check (and combine)
+ * properties of underlying devices.
+ * E.g. Does at least one underlying device support flush?
+ *      Does any underlying device not support WRITE_SAME?
+ *
+ * The callout function is called once for each contiguous section of
+ * an underlying device.  State can be maintained in *data.
+ * Return non-zero to stop iterating through any further devices.
+ */
 typedef int (*iterate_devices_callout_fn) (struct dm_target *ti,
 					   struct dm_dev *dev,
 					   sector_t start, sector_t len,
 					   void *data);
 
+/*
+ * This function must iterate through each section of device used by the
+ * target until it encounters a non-zero return code, which it then returns.
+ * Returns zero if no callout returned non-zero.
+ */
 typedef int (*dm_iterate_devices_fn) (struct dm_target *ti,
 				      iterate_devices_callout_fn fn,
 				      void *data);