From: Omar Sandoval <[email protected]> In elevator_switch(), if blk_mq_init_sched() fails, we attempt to fall back to the original scheduler. However, at this point, we've already torn down the original scheduler's tags, so this causes a crash. Doing the fallback like the legacy elevator path is much harder for mq, so fix it by just falling back to none, instead.
Signed-off-by: Omar Sandoval <[email protected]> --- block/blk-mq-sched.c | 13 +++++-- block/blk-mq-sched.h | 2 +- block/blk-mq.c | 2 -- block/blk-sysfs.c | 2 +- block/elevator.c | 94 +++++++++++++++++++++++++++--------------------- include/linux/elevator.h | 2 +- 6 files changed, 67 insertions(+), 48 deletions(-) diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 0bb13bb51daa..e8c2ed654ef0 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -451,7 +451,7 @@ static int blk_mq_sched_alloc_tags(struct request_queue *q, return ret; } -void blk_mq_sched_teardown(struct request_queue *q) +static void blk_mq_sched_tags_teardown(struct request_queue *q) { struct blk_mq_tag_set *set = q->tag_set; struct blk_mq_hw_ctx *hctx; @@ -513,10 +513,19 @@ int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e) return 0; err: - blk_mq_sched_teardown(q); + blk_mq_sched_tags_teardown(q); + q->elevator = NULL; return ret; } +void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e) +{ + if (e->type->ops.mq.exit_sched) + e->type->ops.mq.exit_sched(e); + blk_mq_sched_tags_teardown(q); + q->elevator = NULL; +} + int blk_mq_sched_init(struct request_queue *q) { int ret; diff --git a/block/blk-mq-sched.h b/block/blk-mq-sched.h index 19db25e0c95a..e704956e0862 100644 --- a/block/blk-mq-sched.h +++ b/block/blk-mq-sched.h @@ -33,7 +33,7 @@ void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx, struct request *(*get_rq)(struct blk_mq_hw_ctx *)); int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e); -void blk_mq_sched_teardown(struct request_queue *q); +void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e); int blk_mq_sched_init_hctx(struct request_queue *q, struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx); diff --git a/block/blk-mq.c b/block/blk-mq.c index 672430c8c342..147cc53134d8 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2137,8 +2137,6 @@ void blk_mq_release(struct request_queue *q) struct blk_mq_hw_ctx *hctx; unsigned int i; - blk_mq_sched_teardown(q); - /* hctx kobj stays in hctx */ queue_for_each_hw_ctx(q, hctx, i) { if (!hctx) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 45854266e398..c47db43a40cc 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -803,7 +803,7 @@ static void blk_release_queue(struct kobject *kobj) if (q->elevator) { ioc_clear_queue(q); - elevator_exit(q->elevator); + elevator_exit(q, q->elevator); } blk_free_queue_stats(q->stats); diff --git a/block/elevator.c b/block/elevator.c index f236ef1d2be9..dbeecf7be719 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -252,11 +252,11 @@ int elevator_init(struct request_queue *q, char *name) } EXPORT_SYMBOL(elevator_init); -void elevator_exit(struct elevator_queue *e) +void elevator_exit(struct request_queue *q, struct elevator_queue *e) { mutex_lock(&e->sysfs_lock); if (e->uses_mq && e->type->ops.mq.exit_sched) - e->type->ops.mq.exit_sched(e); + blk_mq_exit_sched(q, e); else if (!e->uses_mq && e->type->ops.sq.elevator_exit_fn) e->type->ops.sq.elevator_exit_fn(e); mutex_unlock(&e->sysfs_lock); @@ -941,6 +941,45 @@ void elv_unregister(struct elevator_type *e) } EXPORT_SYMBOL_GPL(elv_unregister); +static int elevator_switch_mq(struct request_queue *q, + struct elevator_type *new_e) +{ + int ret; + + blk_mq_freeze_queue(q); + blk_mq_quiesce_queue(q); + + if (q->elevator) { + if (q->elevator->registered) + elv_unregister_queue(q); + ioc_clear_queue(q); + elevator_exit(q, q->elevator); + } + + ret = blk_mq_init_sched(q, new_e); + if (ret) + goto out; + + if (new_e) { + ret = elv_register_queue(q); + if (ret) { + elevator_exit(q, q->elevator); + goto out; + } + } + + if (new_e) + blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); + else + blk_add_trace_msg(q, "elv switch: none"); + +out: + blk_mq_unfreeze_queue(q); + blk_mq_start_stopped_hw_queues(q, true); + return ret; + +} + /* * switch to new_e io scheduler. be careful not to introduce deadlocks - * we don't free the old io scheduler, before we have allocated what we @@ -953,10 +992,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) bool old_registered = false; int err; - if (q->mq_ops) { - blk_mq_freeze_queue(q); - blk_mq_quiesce_queue(q); - } + if (q->mq_ops) + return elevator_switch_mq(q, new_e); /* * Turn on BYPASS and drain all requests w/ elevator private data. @@ -968,11 +1005,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) if (old) { old_registered = old->registered; - if (old->uses_mq) - blk_mq_sched_teardown(q); - - if (!q->mq_ops) - blk_queue_bypass_start(q); + blk_queue_bypass_start(q); /* unregister and clear all auxiliary data of the old elevator */ if (old_registered) @@ -982,53 +1015,32 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) } /* allocate, init and register new elevator */ - if (q->mq_ops) - err = blk_mq_init_sched(q, new_e); - else - err = new_e->ops.sq.elevator_init_fn(q, new_e); + err = new_e->ops.sq.elevator_init_fn(q, new_e); if (err) goto fail_init; - if (new_e) { - err = elv_register_queue(q); - if (err) - goto fail_register; - } + err = elv_register_queue(q); + if (err) + goto fail_register; /* done, kill the old one and finish */ if (old) { - elevator_exit(old); - if (!q->mq_ops) - blk_queue_bypass_end(q); + elevator_exit(q, old); + blk_queue_bypass_end(q); } - if (q->mq_ops) { - blk_mq_unfreeze_queue(q); - blk_mq_start_stopped_hw_queues(q, true); - } - - if (new_e) - blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); - else - blk_add_trace_msg(q, "elv switch: none"); + blk_add_trace_msg(q, "elv switch: %s", new_e->elevator_name); return 0; fail_register: - if (q->mq_ops) - blk_mq_sched_teardown(q); - elevator_exit(q->elevator); + elevator_exit(q, q->elevator); fail_init: /* switch failed, restore and re-register old elevator */ if (old) { q->elevator = old; elv_register_queue(q); - if (!q->mq_ops) - blk_queue_bypass_end(q); - } - if (q->mq_ops) { - blk_mq_unfreeze_queue(q); - blk_mq_start_stopped_hw_queues(q, true); + blk_queue_bypass_end(q); } return err; diff --git a/include/linux/elevator.h b/include/linux/elevator.h index aebecc4ed088..22d39e8d4de1 100644 --- a/include/linux/elevator.h +++ b/include/linux/elevator.h @@ -211,7 +211,7 @@ extern ssize_t elv_iosched_show(struct request_queue *, char *); extern ssize_t elv_iosched_store(struct request_queue *, const char *, size_t); extern int elevator_init(struct request_queue *, char *); -extern void elevator_exit(struct elevator_queue *); +extern void elevator_exit(struct request_queue *, struct elevator_queue *); extern int elevator_change(struct request_queue *, const char *); extern bool elv_bio_merge_ok(struct request *, struct bio *); extern struct elevator_queue *elevator_alloc(struct request_queue *, -- 2.12.2
