path: root/drivers/md/dm-path-selector.h
diff options
authorKiyoshi Ueda <>2009-06-22 10:12:27 +0100
committerAlasdair G Kergon <>2009-06-22 10:12:27 +0100
commit02ab823fd1a27d193bda06b74fdad685a20a3e5e (patch)
tree04b3db6e494f483fef34a55e487e88f6d7c585a5 /drivers/md/dm-path-selector.h
parent2bd023452592e5f5cf90dd426cc39b7632b15b76 (diff)
dm mpath: add start_io and nr_bytes to path selectors
This patch makes two additions to the dm path selector interface for dynamic load balancers: o a new hook, start_io() o a new parameter 'nr_bytes' to select_path()/start_io()/end_io() to pass the size of the I/O start_io() is called when a target driver actually submits I/O to the selected path. Path selectors can use it to start accounting of the I/O. (e.g. counting the number of in-flight I/Os.) The start_io hook is based on the patch posted by Stefan Bader: nr_bytes, the size of the I/O, is so path selectors can take the size of the I/O into account when deciding which path to use. dm-service-time uses it to estimate service time, for example. (Added the nr_bytes member to dm_mpath_io instead of using existing details.bi_size, since request-based dm patch deletes it.) Signed-off-by: Stefan Bader <> Signed-off-by: Kiyoshi Ueda <> Signed-off-by: Jun'ichi Nomura <> Signed-off-by: Alasdair G Kergon <>
Diffstat (limited to 'drivers/md/dm-path-selector.h')
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/md/dm-path-selector.h b/drivers/md/dm-path-selector.h
index 27357b85d73d..e7d1fa8b0459 100644
--- a/drivers/md/dm-path-selector.h
+++ b/drivers/md/dm-path-selector.h
@@ -56,7 +56,8 @@ struct path_selector_type {
* the path fails.
struct dm_path *(*select_path) (struct path_selector *ps,
- unsigned *repeat_count);
+ unsigned *repeat_count,
+ size_t nr_bytes);
* Notify the selector that a path has failed.
@@ -75,7 +76,10 @@ struct path_selector_type {
int (*status) (struct path_selector *ps, struct dm_path *path,
status_type_t type, char *result, unsigned int maxlen);
- int (*end_io) (struct path_selector *ps, struct dm_path *path);
+ int (*start_io) (struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes);
+ int (*end_io) (struct path_selector *ps, struct dm_path *path,
+ size_t nr_bytes);
/* Register a path selector */