#endif
data->ctx->rq_dispatched[op_is_sync(op)]++;
+ refcount_set(&rq->ref, 1);
return rq;
}
}
EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
+static void __blk_mq_free_request(struct request *rq)
+{
+ struct request_queue *q = rq->q;
+ struct blk_mq_ctx *ctx = rq->mq_ctx;
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+ const int sched_tag = rq->internal_tag;
+
+ if (rq->tag != -1)
+ blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
+ if (sched_tag != -1)
+ blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
+ blk_mq_sched_restart(hctx);
+ blk_queue_exit(q);
+}
+
void blk_mq_free_request(struct request *rq)
{
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 = blk_mq_map_queue(q, ctx->cpu);
- const int sched_tag = rq->internal_tag;
if (rq->rq_flags & RQF_ELVPRIV) {
if (e && e->type->ops.mq.finish_request)
if (blk_rq_rl(rq))
blk_put_rl(blk_rq_rl(rq));
- blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
- if (rq->tag != -1)
- blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
- if (sched_tag != -1)
- blk_mq_put_tag(hctx, hctx->sched_tags, ctx, sched_tag);
- blk_mq_sched_restart(hctx);
- blk_queue_exit(q);
+ WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+ if (refcount_dec_and_test(&rq->ref))
+ __blk_mq_free_request(rq);
}
EXPORT_SYMBOL_GPL(blk_mq_free_request);
bool shared = false;
int cpu;
- WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT);
- blk_mq_rq_update_state(rq, MQ_RQ_COMPLETE);
+ if (cmpxchg(&rq->state, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE) !=
+ MQ_RQ_IN_FLIGHT)
+ return;
if (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq);
*srcu_idx = srcu_read_lock(hctx->srcu);
}
-static void blk_mq_rq_update_aborted_gstate(struct request *rq, u64 gstate)
-{
- unsigned long flags;
-
- /*
- * blk_mq_rq_aborted_gstate() is used from the completion path and
- * can thus be called from irq context. u64_stats_fetch in the
- * middle of update on the same CPU leads to lockup. Disable irq
- * while updating.
- */
- local_irq_save(flags);
- u64_stats_update_begin(&rq->aborted_gstate_sync);
- rq->aborted_gstate = gstate;
- u64_stats_update_end(&rq->aborted_gstate_sync);
- local_irq_restore(flags);
-}
-
-static u64 blk_mq_rq_aborted_gstate(struct request *rq)
-{
- unsigned int start;
- u64 aborted_gstate;
-
- do {
- start = u64_stats_fetch_begin(&rq->aborted_gstate_sync);
- aborted_gstate = rq->aborted_gstate;
- } while (u64_stats_fetch_retry(&rq->aborted_gstate_sync, start));
-
- return aborted_gstate;
-}
-
/**
* blk_mq_complete_request - end I/O on a request
* @rq: the request being processed
**/
void blk_mq_complete_request(struct request *rq)
{
- struct request_queue *q = rq->q;
- struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
- int srcu_idx;
-
- if (unlikely(blk_should_fake_timeout(q)))
+ if (unlikely(blk_should_fake_timeout(rq->q)))
return;
-
- /*
- * If @rq->aborted_gstate equals the current instance, timeout is
- * claiming @rq and we lost. This is synchronized through
- * hctx_lock(). See blk_mq_timeout_work() for details.
- *
- * Completion path never blocks and we can directly use RCU here
- * instead of hctx_lock() which can be either RCU or SRCU.
- * However, that would complicate paths which want to synchronize
- * against us. Let stay in sync with the issue path so that
- * hctx_lock() covers both issue and completion paths.
- */
- hctx_lock(hctx, &srcu_idx);
- if (blk_mq_rq_aborted_gstate(rq) != rq->gstate)
- __blk_mq_complete_request(rq);
- hctx_unlock(hctx, srcu_idx);
+ __blk_mq_complete_request(rq);
}
EXPORT_SYMBOL(blk_mq_complete_request);
WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
- /*
- * Mark @rq in-flight which also advances the generation number,
- * and register for timeout. Protect with a seqcount to allow the
- * timeout path to read both @rq->gstate and @rq->deadline
- * coherently.
- *
- * This is the only place where a request is marked in-flight. If
- * the timeout path reads an in-flight @rq->gstate, the
- * @rq->deadline it reads together under @rq->gstate_seq is
- * guaranteed to be the matching one.
- */
- preempt_disable();
- write_seqcount_begin(&rq->gstate_seq);
-
blk_add_timer(rq);
- blk_mq_rq_update_state(rq, MQ_RQ_IN_FLIGHT);
-
- write_seqcount_end(&rq->gstate_seq);
- preempt_enable();
+ WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
}
EXPORT_SYMBOL(blk_mq_start_request);
-/*
- * When we reach here because queue is busy, it's safe to change the state
- * to IDLE without checking @rq->aborted_gstate because we should still be
- * holding the RCU read lock and thus protected against timeout.
- */
static void __blk_mq_requeue_request(struct request *rq)
{
struct request_queue *q = rq->q;
trace_block_rq_requeue(q, rq);
wbt_requeue(q->rq_wb, rq);
- if (blk_mq_rq_state(rq) != MQ_RQ_IDLE) {
- blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
+ if (blk_mq_request_started(rq)) {
+ WRITE_ONCE(rq->state, MQ_RQ_IDLE);
if (q->dma_drain_size && blk_rq_bytes(rq))
rq->nr_phys_segments--;
}
}
EXPORT_SYMBOL(blk_mq_tag_to_rq);
-struct blk_mq_timeout_data {
- unsigned long next;
- unsigned int next_set;
- unsigned int nr_expired;
-};
-
static void blk_mq_rq_timed_out(struct request *req, bool reserved)
{
const struct blk_mq_ops *ops = req->q->mq_ops;
enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
- req->rq_flags |= RQF_MQ_TIMEOUT_EXPIRED;
-
if (ops->timeout)
ret = ops->timeout(req, reserved);
switch (ret) {
case BLK_EH_HANDLED:
- __blk_mq_complete_request(req);
+ if (blk_mq_rq_state(req) == MQ_RQ_IN_FLIGHT)
+ __blk_mq_complete_request(req);
break;
case BLK_EH_RESET_TIMER:
- /*
- * As nothing prevents from completion happening while
- * ->aborted_gstate is set, this may lead to ignored
- * completions and further spurious timeouts.
- */
- blk_mq_rq_update_aborted_gstate(req, 0);
blk_add_timer(req);
break;
case BLK_EH_NOT_HANDLED:
}
}
-static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
- struct request *rq, void *priv, bool reserved)
+static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
{
- struct blk_mq_timeout_data *data = priv;
- unsigned long gstate, deadline;
- int start;
+ unsigned long deadline;
- might_sleep();
-
- if (rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED)
- return;
+ if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
+ return false;
- /* read coherent snapshots of @rq->state_gen and @rq->deadline */
- while (true) {
- start = read_seqcount_begin(&rq->gstate_seq);
- gstate = READ_ONCE(rq->gstate);
- deadline = blk_rq_deadline(rq);
- if (!read_seqcount_retry(&rq->gstate_seq, start))
- break;
- cond_resched();
- }
+ deadline = blk_rq_deadline(rq);
+ if (time_after_eq(jiffies, deadline))
+ return true;
- /* if in-flight && overdue, mark for abortion */
- if ((gstate & MQ_RQ_STATE_MASK) == MQ_RQ_IN_FLIGHT &&
- time_after_eq(jiffies, deadline)) {
- blk_mq_rq_update_aborted_gstate(rq, gstate);
- data->nr_expired++;
- hctx->nr_expired++;
- } else if (!data->next_set || time_after(data->next, deadline)) {
- data->next = deadline;
- data->next_set = 1;
- }
+ if (*next == 0)
+ *next = deadline;
+ else if (time_after(*next, deadline))
+ *next = deadline;
+ return false;
}
-static void blk_mq_terminate_expired(struct blk_mq_hw_ctx *hctx,
+static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
struct request *rq, void *priv, bool reserved)
{
+ unsigned long *next = priv;
+
+ /*
+ * Just do a quick check if it is expired before locking the request in
+ * so we're not unnecessarilly synchronizing across CPUs.
+ */
+ if (!blk_mq_req_expired(rq, next))
+ return;
+
+ /*
+ * We have reason to believe the request may be expired. Take a
+ * reference on the request to lock this request lifetime into its
+ * currently allocated context to prevent it from being reallocated in
+ * the event the completion by-passes this timeout handler.
+ *
+ * If the reference was already released, then the driver beat the
+ * timeout handler to posting a natural completion.
+ */
+ if (!refcount_inc_not_zero(&rq->ref))
+ return;
+
/*
- * We marked @rq->aborted_gstate and waited for RCU. If there were
- * completions that we lost to, they would have finished and
- * updated @rq->gstate by now; otherwise, the completion path is
- * now guaranteed to see @rq->aborted_gstate and yield. If
- * @rq->aborted_gstate still matches @rq->gstate, @rq is ours.
+ * The request is now locked and cannot be reallocated underneath the
+ * timeout handler's processing. Re-verify this exact request is truly
+ * expired; if it is not expired, then the request was completed and
+ * reallocated as a new request.
*/
- if (!(rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) &&
- READ_ONCE(rq->gstate) == rq->aborted_gstate)
+ if (blk_mq_req_expired(rq, next))
blk_mq_rq_timed_out(rq, reserved);
+ if (refcount_dec_and_test(&rq->ref))
+ __blk_mq_free_request(rq);
}
static void blk_mq_timeout_work(struct work_struct *work)
{
struct request_queue *q =
container_of(work, struct request_queue, timeout_work);
- struct blk_mq_timeout_data data = {
- .next = 0,
- .next_set = 0,
- .nr_expired = 0,
- };
+ unsigned long next = 0;
struct blk_mq_hw_ctx *hctx;
int i;
if (!percpu_ref_tryget(&q->q_usage_counter))
return;
- /* scan for the expired ones and set their ->aborted_gstate */
- blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &data);
+ blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
- if (data.nr_expired) {
- bool has_rcu = false;
-
- /*
- * Wait till everyone sees ->aborted_gstate. The
- * sequential waits for SRCUs aren't ideal. If this ever
- * becomes a problem, we can add per-hw_ctx rcu_head and
- * wait in parallel.
- */
- queue_for_each_hw_ctx(q, hctx, i) {
- if (!hctx->nr_expired)
- continue;
-
- if (!(hctx->flags & BLK_MQ_F_BLOCKING))
- has_rcu = true;
- else
- synchronize_srcu(hctx->srcu);
-
- hctx->nr_expired = 0;
- }
- if (has_rcu)
- synchronize_rcu();
-
- /* terminate the ones we won */
- blk_mq_queue_tag_busy_iter(q, blk_mq_terminate_expired, NULL);
- }
-
- if (data.next_set) {
- data.next = blk_rq_timeout(round_jiffies_up(data.next));
- mod_timer(&q->timeout, data.next);
+ if (next != 0) {
+ mod_timer(&q->timeout, next);
} else {
/*
* Request timeouts are handled as a forward rolling timer. If
return ret;
}
- seqcount_init(&rq->gstate_seq);
- u64_stats_init(&rq->aborted_gstate_sync);
- /*
- * start gstate with gen 1 instead of 0, otherwise it will be equal
- * to aborted_gstate, and be identified timed out by
- * blk_mq_terminate_expired.
- */
- WRITE_ONCE(rq->gstate, MQ_RQ_GEN_INC);
-
+ WRITE_ONCE(rq->state, MQ_RQ_IDLE);
return 0;
}
projects / openwrt / staging / blogic.git / commitdiff