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@xxxxxxxxxxxxx> Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx> Cc: Vijayakumar Balasubramanian <vijayakumar@xxxxxx> Cc: Alasdair G Kergon <agk@xxxxxxxxxx> --- 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); }; -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
