From: Kiyoshi Ueda 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: https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html 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 --- drivers/md/dm-mpath.c | 28 ++++++++++++++++++---------- drivers/md/dm-path-selector.h | 8 ++++++-- drivers/md/dm-round-robin.c | 2 +- 3 files changed, 25 insertions(+), 13 deletions(-) Index: linux-2.6.30/drivers/md/dm-mpath.c =================================================================== --- linux-2.6.30.orig/drivers/md/dm-mpath.c +++ linux-2.6.30/drivers/md/dm-mpath.c @@ -101,6 +101,7 @@ struct multipath { struct dm_mpath_io { struct pgpath *pgpath; struct dm_bio_details details; + size_t nr_bytes; }; typedef int (*action_fn) (struct pgpath *pgpath); @@ -244,11 +245,12 @@ static void __switch_pg(struct multipath m->pg_init_count = 0; } -static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg) +static int __choose_path_in_pg(struct multipath *m, struct priority_group *pg, + size_t nr_bytes) { struct dm_path *path; - path = pg->ps.type->select_path(&pg->ps, &m->repeat_count); + path = pg->ps.type->select_path(&pg->ps, &m->repeat_count, nr_bytes); if (!path) return -ENXIO; @@ -260,7 +262,7 @@ static int __choose_path_in_pg(struct mu return 0; } -static void __choose_pgpath(struct multipath *m) +static void __choose_pgpath(struct multipath *m, size_t nr_bytes) { struct priority_group *pg; unsigned bypassed = 1; @@ -272,12 +274,12 @@ static void __choose_pgpath(struct multi if (m->next_pg) { pg = m->next_pg; m->next_pg = NULL; - if (!__choose_path_in_pg(m, pg)) + if (!__choose_path_in_pg(m, pg, nr_bytes)) return; } /* Don't change PG until it has no remaining paths */ - if (m->current_pg && !__choose_path_in_pg(m, m->current_pg)) + if (m->current_pg && !__choose_path_in_pg(m, m->current_pg, nr_bytes)) return; /* @@ -289,7 +291,7 @@ static void __choose_pgpath(struct multi list_for_each_entry(pg, &m->priority_groups, list) { if (pg->bypassed == bypassed) continue; - if (!__choose_path_in_pg(m, pg)) + if (!__choose_path_in_pg(m, pg, nr_bytes)) return; } } while (bypassed--); @@ -320,6 +322,7 @@ static int map_io(struct multipath *m, s struct dm_mpath_io *mpio, unsigned was_queued) { int r = DM_MAPIO_REMAPPED; + size_t nr_bytes = bio->bi_size; unsigned long flags; struct pgpath *pgpath; @@ -328,7 +331,7 @@ static int map_io(struct multipath *m, s /* Do we need to select a new pgpath? */ if (!m->current_pgpath || (!m->queue_io && (m->repeat_count && --m->repeat_count == 0))) - __choose_pgpath(m); + __choose_pgpath(m, nr_bytes); pgpath = m->current_pgpath; @@ -353,6 +356,11 @@ static int map_io(struct multipath *m, s r = -EIO; /* Failed */ mpio->pgpath = pgpath; + mpio->nr_bytes = nr_bytes; + + if (r == DM_MAPIO_REMAPPED && pgpath->pg->ps.type->start_io) + pgpath->pg->ps.type->start_io(&pgpath->pg->ps, &pgpath->path, + nr_bytes); spin_unlock_irqrestore(&m->lock, flags); @@ -431,7 +439,7 @@ static void process_queued_ios(struct wo goto out; if (!m->current_pgpath) - __choose_pgpath(m); + __choose_pgpath(m, 0); pgpath = m->current_pgpath; @@ -1209,7 +1217,7 @@ static int multipath_end_io(struct dm_ta if (pgpath) { ps = &pgpath->pg->ps; if (ps->type->end_io) - ps->type->end_io(ps, &pgpath->path); + ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes); } if (r != DM_ENDIO_INCOMPLETE) mempool_free(mpio, m->mpio_pool); @@ -1425,7 +1433,7 @@ static int multipath_ioctl(struct dm_tar spin_lock_irqsave(&m->lock, flags); if (!m->current_pgpath) - __choose_pgpath(m); + __choose_pgpath(m, 0); if (m->current_pgpath) { bdev = m->current_pgpath->path.dev->bdev; Index: linux-2.6.30/drivers/md/dm-path-selector.h =================================================================== --- linux-2.6.30.orig/drivers/md/dm-path-selector.h +++ linux-2.6.30/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 */ Index: linux-2.6.30/drivers/md/dm-round-robin.c =================================================================== --- linux-2.6.30.orig/drivers/md/dm-round-robin.c +++ linux-2.6.30/drivers/md/dm-round-robin.c @@ -161,7 +161,7 @@ static int rr_reinstate_path(struct path } static struct dm_path *rr_select_path(struct path_selector *ps, - unsigned *repeat_count) + unsigned *repeat_count, size_t nr_bytes) { struct selector *s = (struct selector *) ps->context; struct path_info *pi = NULL;