From 72e06c255181537d0b3e1f657a9ed81655d745b1 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 5 Mar 2012 13:15:00 -0800 Subject: blkcg: shoot down blkio_groups on elevator switch Elevator switch may involve changes to blkcg policies. Implement shoot down of blkio_groups. Combined with the previous bypass updates, the end goal is updating blkcg core such that it can ensure that blkcg's being affected become quiescent and don't have any per-blkg data hanging around before commencing any policy updates. Until queues are made aware of the policies that applies to them, as an interim step, all per-policy blkg data will be shot down. * blk-throtl doesn't need this change as it can't be disabled for a live queue; however, update it anyway as the scheduled blkg unification requires this behavior change. This means that blk-throtl configuration will be unnecessarily lost over elevator switch. This oddity will be removed after blkcg learns to associate individual policies with request_queues. * blk-throtl dosen't shoot down root_tg. This is to ease transition. Unified blkg will always have persistent root group and not shooting down root_tg for now eases transition to that point by avoiding having to update td->root_tg and is safe as blk-throtl can never be disabled -v2: Vivek pointed out that group list is not guaranteed to be empty on return from clear function if it raced cgroup removal and lost. Fix it by waiting a bit and retrying. This kludge will soon be removed once locking is updated such that blkg is never in limbo state between blkcg and request_queue locks. blk-throtl no longer shoots down root_tg to avoid breaking td->root_tg. Also, Nest queue_lock inside blkio_list_lock not the other way around to avoid introduce possible deadlock via blkcg lock. -v3: blkcg_clear_queue() repositioned and renamed to blkg_destroy_all() to increase consistency with later changes. cfq_clear_queue() updated to check q->elevator before dereferencing it to avoid NULL dereference on not fully initialized queues (used by later change). Signed-off-by: Tejun Heo Cc: Vivek Goyal Signed-off-by: Jens Axboe --- block/blk-cgroup.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'block/blk-cgroup.h') diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 355168772f51..e5cfcbd4d2f4 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -203,7 +203,7 @@ extern unsigned int blkcg_get_write_iops(struct blkio_cgroup *blkcg, dev_t dev); typedef void (blkio_unlink_group_fn) (void *key, struct blkio_group *blkg); - +typedef bool (blkio_clear_queue_fn)(struct request_queue *q); typedef void (blkio_update_group_weight_fn) (void *key, struct blkio_group *blkg, unsigned int weight); typedef void (blkio_update_group_read_bps_fn) (void * key, @@ -217,6 +217,7 @@ typedef void (blkio_update_group_write_iops_fn) (void *key, struct blkio_policy_ops { blkio_unlink_group_fn *blkio_unlink_group_fn; + blkio_clear_queue_fn *blkio_clear_queue_fn; blkio_update_group_weight_fn *blkio_update_group_weight_fn; blkio_update_group_read_bps_fn *blkio_update_group_read_bps_fn; blkio_update_group_write_bps_fn *blkio_update_group_write_bps_fn; @@ -233,6 +234,7 @@ struct blkio_policy_type { /* Blkio controller policy registration */ extern void blkio_policy_register(struct blkio_policy_type *); extern void blkio_policy_unregister(struct blkio_policy_type *); +extern void blkg_destroy_all(struct request_queue *q); static inline char *blkg_path(struct blkio_group *blkg) { @@ -249,6 +251,7 @@ struct blkio_policy_type { static inline void blkio_policy_register(struct blkio_policy_type *blkiop) { } static inline void blkio_policy_unregister(struct blkio_policy_type *blkiop) { } +static inline void blkg_destroy_all(struct request_queue *q) { } static inline char *blkg_path(struct blkio_group *blkg) { return NULL; } -- cgit v1.2.3