This patch adds a new hook for dm path selector: start_io.
Target drivers should call this hook before submitting 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 code is based on the patch posted by Stefan Bader:
https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: Vijayakumar Balasubramanian <vijayakumar@hp.com>
Cc: Alasdair G Kergon <agk@redhat.com>
---
drivers/md/dm-mpath.c | 3 +++
drivers/md/dm-path-selector.h | 1 +
2 files changed, 4 insertions(+)
Index: 2.6.29-rc2/drivers/md/dm-mpath.c
================================================== =================
--- 2.6.29-rc2.orig/drivers/md/dm-mpath.c
+++ 2.6.29-rc2/drivers/md/dm-mpath.c
@@ -361,6 +361,9 @@ static int map_io(struct multipath *m, s
mpio->pgpath = pgpath;
+ if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io)
+ pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path);
+
spin_unlock_irqrestore(&m->lock, flags);
return r;
Index: 2.6.29-rc2/drivers/md/dm-path-selector.h
================================================== =================
--- 2.6.29-rc2.orig/drivers/md/dm-path-selector.h
+++ 2.6.29-rc2/drivers/md/dm-path-selector.h
@@ -75,6 +75,7 @@ struct path_selector_type {
int (*status) (struct path_selector *ps, struct dm_path *path,
status_type_t type, char *result, unsigned int maxlen);
+ int (*start_io) (struct path_selector *ps, struct dm_path *path);
int (*end_io) (struct path_selector *ps, struct dm_path *path);
};
--
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dm-mpath: add a path selector interface
