mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-22 18:44:44 +08:00
e87eb301be
Just like aio/io_uring, we need to grab 2 refcount for queuing one request, one is for submission, another is for completion. If the request isn't queued from plug code path, the refcount grabbed in generic_make_request() serves for submission. In theroy, this refcount should have been released after the sumission(async run queue) is done. blk_freeze_queue() works with blk_sync_queue() together for avoiding race between cleanup queue and IO submission, given async run queue activities are canceled because hctx->run_work is scheduled with the refcount held, so it is fine to not hold the refcount when running the run queue work function for dispatch IO. However, if request is staggered into plug list, and finally queued from plug code path, the refcount in submission side is actually missed. And we may start to run queue after queue is removed because the queue's kobject refcount isn't guaranteed to be grabbed in flushing plug list context, then kernel oops is triggered, see the following race: blk_mq_flush_plug_list(): blk_mq_sched_insert_requests() insert requests to sw queue or scheduler queue blk_mq_run_hw_queue Because of concurrent run queue, all requests inserted above may be completed before calling the above blk_mq_run_hw_queue. Then queue can be freed during the above blk_mq_run_hw_queue(). Fixes the issue by grab .q_usage_counter before calling blk_mq_sched_insert_requests() in blk_mq_flush_plug_list(). This way is safe because the queue is absolutely alive before inserting request. Cc: Dongli Zhang <dongli.zhang@oracle.com> Cc: James Smart <james.smart@broadcom.com> Cc: linux-scsi@vger.kernel.org, Cc: Martin K . Petersen <martin.petersen@oracle.com>, Cc: Christoph Hellwig <hch@lst.de>, Cc: James E . J . Bottomley <jejb@linux.vnet.ibm.com>, Reviewed-by: Bart Van Assche <bvanassche@acm.org> Tested-by: James Smart <james.smart@broadcom.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
560 lines
14 KiB
C
560 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* blk-mq scheduling framework
|
|
*
|
|
* Copyright (C) 2016 Jens Axboe
|
|
*/
|
|
#include <linux/kernel.h>
|
|
#include <linux/module.h>
|
|
#include <linux/blk-mq.h>
|
|
|
|
#include <trace/events/block.h>
|
|
|
|
#include "blk.h"
|
|
#include "blk-mq.h"
|
|
#include "blk-mq-debugfs.h"
|
|
#include "blk-mq-sched.h"
|
|
#include "blk-mq-tag.h"
|
|
#include "blk-wbt.h"
|
|
|
|
void blk_mq_sched_free_hctx_data(struct request_queue *q,
|
|
void (*exit)(struct blk_mq_hw_ctx *))
|
|
{
|
|
struct blk_mq_hw_ctx *hctx;
|
|
int i;
|
|
|
|
queue_for_each_hw_ctx(q, hctx, i) {
|
|
if (exit && hctx->sched_data)
|
|
exit(hctx);
|
|
kfree(hctx->sched_data);
|
|
hctx->sched_data = NULL;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
|
|
|
|
void blk_mq_sched_assign_ioc(struct request *rq)
|
|
{
|
|
struct request_queue *q = rq->q;
|
|
struct io_context *ioc;
|
|
struct io_cq *icq;
|
|
|
|
/*
|
|
* May not have an IO context if it's a passthrough request
|
|
*/
|
|
ioc = current->io_context;
|
|
if (!ioc)
|
|
return;
|
|
|
|
spin_lock_irq(&q->queue_lock);
|
|
icq = ioc_lookup_icq(ioc, q);
|
|
spin_unlock_irq(&q->queue_lock);
|
|
|
|
if (!icq) {
|
|
icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
|
|
if (!icq)
|
|
return;
|
|
}
|
|
get_io_context(icq->ioc);
|
|
rq->elv.icq = icq;
|
|
}
|
|
|
|
/*
|
|
* Mark a hardware queue as needing a restart. For shared queues, maintain
|
|
* a count of how many hardware queues are marked for restart.
|
|
*/
|
|
void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
|
|
return;
|
|
|
|
set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_mark_restart_hctx);
|
|
|
|
void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
|
|
return;
|
|
clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
|
|
|
|
blk_mq_run_hw_queue(hctx, true);
|
|
}
|
|
|
|
/*
|
|
* Only SCSI implements .get_budget and .put_budget, and SCSI restarts
|
|
* its queue by itself in its completion handler, so we don't need to
|
|
* restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
|
|
*/
|
|
static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct request_queue *q = hctx->queue;
|
|
struct elevator_queue *e = q->elevator;
|
|
LIST_HEAD(rq_list);
|
|
|
|
do {
|
|
struct request *rq;
|
|
|
|
if (e->type->ops.has_work && !e->type->ops.has_work(hctx))
|
|
break;
|
|
|
|
if (!blk_mq_get_dispatch_budget(hctx))
|
|
break;
|
|
|
|
rq = e->type->ops.dispatch_request(hctx);
|
|
if (!rq) {
|
|
blk_mq_put_dispatch_budget(hctx);
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Now this rq owns the budget which has to be released
|
|
* if this rq won't be queued to driver via .queue_rq()
|
|
* in blk_mq_dispatch_rq_list().
|
|
*/
|
|
list_add(&rq->queuelist, &rq_list);
|
|
} while (blk_mq_dispatch_rq_list(q, &rq_list, true));
|
|
}
|
|
|
|
static struct blk_mq_ctx *blk_mq_next_ctx(struct blk_mq_hw_ctx *hctx,
|
|
struct blk_mq_ctx *ctx)
|
|
{
|
|
unsigned short idx = ctx->index_hw[hctx->type];
|
|
|
|
if (++idx == hctx->nr_ctx)
|
|
idx = 0;
|
|
|
|
return hctx->ctxs[idx];
|
|
}
|
|
|
|
/*
|
|
* Only SCSI implements .get_budget and .put_budget, and SCSI restarts
|
|
* its queue by itself in its completion handler, so we don't need to
|
|
* restart queue if .get_budget() returns BLK_STS_NO_RESOURCE.
|
|
*/
|
|
static void blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct request_queue *q = hctx->queue;
|
|
LIST_HEAD(rq_list);
|
|
struct blk_mq_ctx *ctx = READ_ONCE(hctx->dispatch_from);
|
|
|
|
do {
|
|
struct request *rq;
|
|
|
|
if (!sbitmap_any_bit_set(&hctx->ctx_map))
|
|
break;
|
|
|
|
if (!blk_mq_get_dispatch_budget(hctx))
|
|
break;
|
|
|
|
rq = blk_mq_dequeue_from_ctx(hctx, ctx);
|
|
if (!rq) {
|
|
blk_mq_put_dispatch_budget(hctx);
|
|
break;
|
|
}
|
|
|
|
/*
|
|
* Now this rq owns the budget which has to be released
|
|
* if this rq won't be queued to driver via .queue_rq()
|
|
* in blk_mq_dispatch_rq_list().
|
|
*/
|
|
list_add(&rq->queuelist, &rq_list);
|
|
|
|
/* round robin for fair dispatch */
|
|
ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
|
|
|
|
} while (blk_mq_dispatch_rq_list(q, &rq_list, true));
|
|
|
|
WRITE_ONCE(hctx->dispatch_from, ctx);
|
|
}
|
|
|
|
void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct request_queue *q = hctx->queue;
|
|
struct elevator_queue *e = q->elevator;
|
|
const bool has_sched_dispatch = e && e->type->ops.dispatch_request;
|
|
LIST_HEAD(rq_list);
|
|
|
|
/* RCU or SRCU read lock is needed before checking quiesced flag */
|
|
if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)))
|
|
return;
|
|
|
|
hctx->run++;
|
|
|
|
/*
|
|
* If we have previous entries on our dispatch list, grab them first for
|
|
* more fair dispatch.
|
|
*/
|
|
if (!list_empty_careful(&hctx->dispatch)) {
|
|
spin_lock(&hctx->lock);
|
|
if (!list_empty(&hctx->dispatch))
|
|
list_splice_init(&hctx->dispatch, &rq_list);
|
|
spin_unlock(&hctx->lock);
|
|
}
|
|
|
|
/*
|
|
* Only ask the scheduler for requests, if we didn't have residual
|
|
* requests from the dispatch list. This is to avoid the case where
|
|
* we only ever dispatch a fraction of the requests available because
|
|
* of low device queue depth. Once we pull requests out of the IO
|
|
* scheduler, we can no longer merge or sort them. So it's best to
|
|
* leave them there for as long as we can. Mark the hw queue as
|
|
* needing a restart in that case.
|
|
*
|
|
* We want to dispatch from the scheduler if there was nothing
|
|
* on the dispatch list or we were able to dispatch from the
|
|
* dispatch list.
|
|
*/
|
|
if (!list_empty(&rq_list)) {
|
|
blk_mq_sched_mark_restart_hctx(hctx);
|
|
if (blk_mq_dispatch_rq_list(q, &rq_list, false)) {
|
|
if (has_sched_dispatch)
|
|
blk_mq_do_dispatch_sched(hctx);
|
|
else
|
|
blk_mq_do_dispatch_ctx(hctx);
|
|
}
|
|
} else if (has_sched_dispatch) {
|
|
blk_mq_do_dispatch_sched(hctx);
|
|
} else if (hctx->dispatch_busy) {
|
|
/* dequeue request one by one from sw queue if queue is busy */
|
|
blk_mq_do_dispatch_ctx(hctx);
|
|
} else {
|
|
blk_mq_flush_busy_ctxs(hctx, &rq_list);
|
|
blk_mq_dispatch_rq_list(q, &rq_list, false);
|
|
}
|
|
}
|
|
|
|
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
|
|
struct request **merged_request)
|
|
{
|
|
struct request *rq;
|
|
|
|
switch (elv_merge(q, &rq, bio)) {
|
|
case ELEVATOR_BACK_MERGE:
|
|
if (!blk_mq_sched_allow_merge(q, rq, bio))
|
|
return false;
|
|
if (!bio_attempt_back_merge(q, rq, bio))
|
|
return false;
|
|
*merged_request = attempt_back_merge(q, rq);
|
|
if (!*merged_request)
|
|
elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
|
|
return true;
|
|
case ELEVATOR_FRONT_MERGE:
|
|
if (!blk_mq_sched_allow_merge(q, rq, bio))
|
|
return false;
|
|
if (!bio_attempt_front_merge(q, rq, bio))
|
|
return false;
|
|
*merged_request = attempt_front_merge(q, rq);
|
|
if (!*merged_request)
|
|
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
|
|
return true;
|
|
case ELEVATOR_DISCARD_MERGE:
|
|
return bio_attempt_discard_merge(q, rq, bio);
|
|
default:
|
|
return false;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
|
|
|
|
/*
|
|
* Iterate list of requests and see if we can merge this bio with any
|
|
* of them.
|
|
*/
|
|
bool blk_mq_bio_list_merge(struct request_queue *q, struct list_head *list,
|
|
struct bio *bio)
|
|
{
|
|
struct request *rq;
|
|
int checked = 8;
|
|
|
|
list_for_each_entry_reverse(rq, list, queuelist) {
|
|
bool merged = false;
|
|
|
|
if (!checked--)
|
|
break;
|
|
|
|
if (!blk_rq_merge_ok(rq, bio))
|
|
continue;
|
|
|
|
switch (blk_try_merge(rq, bio)) {
|
|
case ELEVATOR_BACK_MERGE:
|
|
if (blk_mq_sched_allow_merge(q, rq, bio))
|
|
merged = bio_attempt_back_merge(q, rq, bio);
|
|
break;
|
|
case ELEVATOR_FRONT_MERGE:
|
|
if (blk_mq_sched_allow_merge(q, rq, bio))
|
|
merged = bio_attempt_front_merge(q, rq, bio);
|
|
break;
|
|
case ELEVATOR_DISCARD_MERGE:
|
|
merged = bio_attempt_discard_merge(q, rq, bio);
|
|
break;
|
|
default:
|
|
continue;
|
|
}
|
|
|
|
return merged;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_bio_list_merge);
|
|
|
|
/*
|
|
* Reverse check our software queue for entries that we could potentially
|
|
* merge with. Currently includes a hand-wavy stop count of 8, to not spend
|
|
* too much time checking for merges.
|
|
*/
|
|
static bool blk_mq_attempt_merge(struct request_queue *q,
|
|
struct blk_mq_hw_ctx *hctx,
|
|
struct blk_mq_ctx *ctx, struct bio *bio)
|
|
{
|
|
enum hctx_type type = hctx->type;
|
|
|
|
lockdep_assert_held(&ctx->lock);
|
|
|
|
if (blk_mq_bio_list_merge(q, &ctx->rq_lists[type], bio)) {
|
|
ctx->rq_merged++;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
|
|
{
|
|
struct elevator_queue *e = q->elevator;
|
|
struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
|
|
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
|
|
bool ret = false;
|
|
enum hctx_type type;
|
|
|
|
if (e && e->type->ops.bio_merge) {
|
|
blk_mq_put_ctx(ctx);
|
|
return e->type->ops.bio_merge(hctx, bio);
|
|
}
|
|
|
|
type = hctx->type;
|
|
if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
|
|
!list_empty_careful(&ctx->rq_lists[type])) {
|
|
/* default per sw-queue merge */
|
|
spin_lock(&ctx->lock);
|
|
ret = blk_mq_attempt_merge(q, hctx, ctx, bio);
|
|
spin_unlock(&ctx->lock);
|
|
}
|
|
|
|
blk_mq_put_ctx(ctx);
|
|
return ret;
|
|
}
|
|
|
|
bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
|
|
{
|
|
return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
|
|
|
|
void blk_mq_sched_request_inserted(struct request *rq)
|
|
{
|
|
trace_block_rq_insert(rq->q, rq);
|
|
}
|
|
EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
|
|
|
|
static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
|
|
bool has_sched,
|
|
struct request *rq)
|
|
{
|
|
/* dispatch flush rq directly */
|
|
if (rq->rq_flags & RQF_FLUSH_SEQ) {
|
|
spin_lock(&hctx->lock);
|
|
list_add(&rq->queuelist, &hctx->dispatch);
|
|
spin_unlock(&hctx->lock);
|
|
return true;
|
|
}
|
|
|
|
if (has_sched)
|
|
rq->rq_flags |= RQF_SORTED;
|
|
|
|
return false;
|
|
}
|
|
|
|
void blk_mq_sched_insert_request(struct request *rq, bool at_head,
|
|
bool run_queue, bool async)
|
|
{
|
|
struct request_queue *q = rq->q;
|
|
struct elevator_queue *e = q->elevator;
|
|
struct blk_mq_ctx *ctx = rq->mq_ctx;
|
|
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
|
|
|
|
/* flush rq in flush machinery need to be dispatched directly */
|
|
if (!(rq->rq_flags & RQF_FLUSH_SEQ) && op_is_flush(rq->cmd_flags)) {
|
|
blk_insert_flush(rq);
|
|
goto run;
|
|
}
|
|
|
|
WARN_ON(e && (rq->tag != -1));
|
|
|
|
if (blk_mq_sched_bypass_insert(hctx, !!e, rq))
|
|
goto run;
|
|
|
|
if (e && e->type->ops.insert_requests) {
|
|
LIST_HEAD(list);
|
|
|
|
list_add(&rq->queuelist, &list);
|
|
e->type->ops.insert_requests(hctx, &list, at_head);
|
|
} else {
|
|
spin_lock(&ctx->lock);
|
|
__blk_mq_insert_request(hctx, rq, at_head);
|
|
spin_unlock(&ctx->lock);
|
|
}
|
|
|
|
run:
|
|
if (run_queue)
|
|
blk_mq_run_hw_queue(hctx, async);
|
|
}
|
|
|
|
void blk_mq_sched_insert_requests(struct blk_mq_hw_ctx *hctx,
|
|
struct blk_mq_ctx *ctx,
|
|
struct list_head *list, bool run_queue_async)
|
|
{
|
|
struct elevator_queue *e;
|
|
struct request_queue *q = hctx->queue;
|
|
|
|
/*
|
|
* blk_mq_sched_insert_requests() is called from flush plug
|
|
* context only, and hold one usage counter to prevent queue
|
|
* from being released.
|
|
*/
|
|
percpu_ref_get(&q->q_usage_counter);
|
|
|
|
e = hctx->queue->elevator;
|
|
if (e && e->type->ops.insert_requests)
|
|
e->type->ops.insert_requests(hctx, list, false);
|
|
else {
|
|
/*
|
|
* try to issue requests directly if the hw queue isn't
|
|
* busy in case of 'none' scheduler, and this way may save
|
|
* us one extra enqueue & dequeue to sw queue.
|
|
*/
|
|
if (!hctx->dispatch_busy && !e && !run_queue_async) {
|
|
blk_mq_try_issue_list_directly(hctx, list);
|
|
if (list_empty(list))
|
|
goto out;
|
|
}
|
|
blk_mq_insert_requests(hctx, ctx, list);
|
|
}
|
|
|
|
blk_mq_run_hw_queue(hctx, run_queue_async);
|
|
out:
|
|
percpu_ref_put(&q->q_usage_counter);
|
|
}
|
|
|
|
static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
|
|
struct blk_mq_hw_ctx *hctx,
|
|
unsigned int hctx_idx)
|
|
{
|
|
if (hctx->sched_tags) {
|
|
blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
|
|
blk_mq_free_rq_map(hctx->sched_tags);
|
|
hctx->sched_tags = NULL;
|
|
}
|
|
}
|
|
|
|
static int blk_mq_sched_alloc_tags(struct request_queue *q,
|
|
struct blk_mq_hw_ctx *hctx,
|
|
unsigned int hctx_idx)
|
|
{
|
|
struct blk_mq_tag_set *set = q->tag_set;
|
|
int ret;
|
|
|
|
hctx->sched_tags = blk_mq_alloc_rq_map(set, hctx_idx, q->nr_requests,
|
|
set->reserved_tags);
|
|
if (!hctx->sched_tags)
|
|
return -ENOMEM;
|
|
|
|
ret = blk_mq_alloc_rqs(set, hctx->sched_tags, hctx_idx, q->nr_requests);
|
|
if (ret)
|
|
blk_mq_sched_free_tags(set, hctx, hctx_idx);
|
|
|
|
return ret;
|
|
}
|
|
|
|
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;
|
|
int i;
|
|
|
|
queue_for_each_hw_ctx(q, hctx, i)
|
|
blk_mq_sched_free_tags(set, hctx, i);
|
|
}
|
|
|
|
int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx;
|
|
struct elevator_queue *eq;
|
|
unsigned int i;
|
|
int ret;
|
|
|
|
if (!e) {
|
|
q->elevator = NULL;
|
|
q->nr_requests = q->tag_set->queue_depth;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Default to double of smaller one between hw queue_depth and 128,
|
|
* since we don't split into sync/async like the old code did.
|
|
* Additionally, this is a per-hw queue depth.
|
|
*/
|
|
q->nr_requests = 2 * min_t(unsigned int, q->tag_set->queue_depth,
|
|
BLKDEV_MAX_RQ);
|
|
|
|
queue_for_each_hw_ctx(q, hctx, i) {
|
|
ret = blk_mq_sched_alloc_tags(q, hctx, i);
|
|
if (ret)
|
|
goto err;
|
|
}
|
|
|
|
ret = e->ops.init_sched(q, e);
|
|
if (ret)
|
|
goto err;
|
|
|
|
blk_mq_debugfs_register_sched(q);
|
|
|
|
queue_for_each_hw_ctx(q, hctx, i) {
|
|
if (e->ops.init_hctx) {
|
|
ret = e->ops.init_hctx(hctx, i);
|
|
if (ret) {
|
|
eq = q->elevator;
|
|
blk_mq_exit_sched(q, eq);
|
|
kobject_put(&eq->kobj);
|
|
return ret;
|
|
}
|
|
}
|
|
blk_mq_debugfs_register_sched_hctx(q, hctx);
|
|
}
|
|
|
|
return 0;
|
|
|
|
err:
|
|
blk_mq_sched_tags_teardown(q);
|
|
q->elevator = NULL;
|
|
return ret;
|
|
}
|
|
|
|
void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx;
|
|
unsigned int i;
|
|
|
|
queue_for_each_hw_ctx(q, hctx, i) {
|
|
blk_mq_debugfs_unregister_sched_hctx(hctx);
|
|
if (e->type->ops.exit_hctx && hctx->sched_data) {
|
|
e->type->ops.exit_hctx(hctx, i);
|
|
hctx->sched_data = NULL;
|
|
}
|
|
}
|
|
blk_mq_debugfs_unregister_sched(q);
|
|
if (e->type->ops.exit_sched)
|
|
e->type->ops.exit_sched(e);
|
|
blk_mq_sched_tags_teardown(q);
|
|
q->elevator = NULL;
|
|
}
|