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authorLinus Torvalds <torvalds@linux-foundation.org>2018-01-29 22:51:49 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-01-29 22:51:49 +0300
commit0a4b6e2f80aad46fb55a5cf7b1664c0aef030ee0 (patch)
treecefccd67dc1f27bb45830f6b8065dd4a1c05e83b /block/blk-mq.c
parent9697e9da84299d0d715d515dd2cc48f1eceb277d (diff)
parent796baeeef85a40b3495a907fb7425086e7010102 (diff)
downloadlinux-0a4b6e2f80aad46fb55a5cf7b1664c0aef030ee0.tar.xz
Merge branch 'for-4.16/block' of git://git.kernel.dk/linux-block
Pull block updates from Jens Axboe: "This is the main pull request for block IO related changes for the 4.16 kernel. Nothing major in this pull request, but a good amount of improvements and fixes all over the map. This contains: - BFQ improvements, fixes, and cleanups from Angelo, Chiara, and Paolo. - Support for SMR zones for deadline and mq-deadline from Damien and Christoph. - Set of fixes for bcache by way of Michael Lyle, including fixes from himself, Kent, Rui, Tang, and Coly. - Series from Matias for lightnvm with fixes from Hans Holmberg, Javier, and Matias. Mostly centered around pblk, and the removing rrpc 1.2 in preparation for supporting 2.0. - A couple of NVMe pull requests from Christoph. Nothing major in here, just fixes and cleanups, and support for command tracing from Johannes. - Support for blk-throttle for tracking reads and writes separately. From Joseph Qi. A few cleanups/fixes also for blk-throttle from Weiping. - Series from Mike Snitzer that enables dm to register its queue more logically, something that's alwways been problematic on dm since it's a stacked device. - Series from Ming cleaning up some of the bio accessor use, in preparation for supporting multipage bvecs. - Various fixes from Ming closing up holes around queue mapping and quiescing. - BSD partition fix from Richard Narron, fixing a problem where we can't mount newer (10/11) FreeBSD partitions. - Series from Tejun reworking blk-mq timeout handling. The previous scheme relied on atomic bits, but it had races where we would think a request had timed out if it to reused at the wrong time. - null_blk now supports faking timeouts, to enable us to better exercise and test that functionality separately. From me. - Kill the separate atomic poll bit in the request struct. After this, we don't use the atomic bits on blk-mq anymore at all. From me. - sgl_alloc/free helpers from Bart. - Heavily contended tag case scalability improvement from me. - Various little fixes and cleanups from Arnd, Bart, Corentin, Douglas, Eryu, Goldwyn, and myself" * 'for-4.16/block' of git://git.kernel.dk/linux-block: (186 commits) block: remove smart1,2.h nvme: add tracepoint for nvme_complete_rq nvme: add tracepoint for nvme_setup_cmd nvme-pci: introduce RECONNECTING state to mark initializing procedure nvme-rdma: remove redundant boolean for inline_data nvme: don't free uuid pointer before printing it nvme-pci: Suspend queues after deleting them bsg: use pr_debug instead of hand crafted macros blk-mq-debugfs: don't allow write on attributes with seq_operations set nvme-pci: Fix queue double allocations block: Set BIO_TRACE_COMPLETION on new bio during split blk-throttle: use queue_is_rq_based block: Remove kblockd_schedule_delayed_work{,_on}() blk-mq: Avoid that blk_mq_delay_run_hw_queue() introduces unintended delays blk-mq: Rename blk_mq_request_direct_issue() into blk_mq_request_issue_directly() lib/scatterlist: Fix chaining support in sgl_alloc_order() blk-throttle: track read and write request individually block: add bdev_read_only() checks to common helpers block: fail op_is_write() requests to read-only partitions blk-throttle: export io_serviced_recursive, io_service_bytes_recursive ...
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c667
1 files changed, 437 insertions, 230 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3d3797327491..01f271d40825 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -95,8 +95,7 @@ static void blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
{
struct mq_inflight *mi = priv;
- if (test_bit(REQ_ATOM_STARTED, &rq->atomic_flags) &&
- !test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags)) {
+ if (blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT) {
/*
* index[0] counts the specific partition that was asked
* for. index[1] counts the ones that are active on the
@@ -222,7 +221,7 @@ void blk_mq_quiesce_queue(struct request_queue *q)
queue_for_each_hw_ctx(q, hctx, i) {
if (hctx->flags & BLK_MQ_F_BLOCKING)
- synchronize_srcu(hctx->queue_rq_srcu);
+ synchronize_srcu(hctx->srcu);
else
rcu = true;
}
@@ -272,15 +271,14 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
{
struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
struct request *rq = tags->static_rqs[tag];
-
- rq->rq_flags = 0;
+ req_flags_t rq_flags = 0;
if (data->flags & BLK_MQ_REQ_INTERNAL) {
rq->tag = -1;
rq->internal_tag = tag;
} else {
if (blk_mq_tag_busy(data->hctx)) {
- rq->rq_flags = RQF_MQ_INFLIGHT;
+ rq_flags = RQF_MQ_INFLIGHT;
atomic_inc(&data->hctx->nr_active);
}
rq->tag = tag;
@@ -288,27 +286,22 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
data->hctx->tags->rqs[rq->tag] = rq;
}
- INIT_LIST_HEAD(&rq->queuelist);
/* csd/requeue_work/fifo_time is initialized before use */
rq->q = data->q;
rq->mq_ctx = data->ctx;
+ rq->rq_flags = rq_flags;
+ rq->cpu = -1;
rq->cmd_flags = op;
if (data->flags & BLK_MQ_REQ_PREEMPT)
rq->rq_flags |= RQF_PREEMPT;
if (blk_queue_io_stat(data->q))
rq->rq_flags |= RQF_IO_STAT;
- /* do not touch atomic flags, it needs atomic ops against the timer */
- rq->cpu = -1;
+ INIT_LIST_HEAD(&rq->queuelist);
INIT_HLIST_NODE(&rq->hash);
RB_CLEAR_NODE(&rq->rb_node);
rq->rq_disk = NULL;
rq->part = NULL;
rq->start_time = jiffies;
-#ifdef CONFIG_BLK_CGROUP
- rq->rl = NULL;
- set_start_time_ns(rq);
- rq->io_start_time_ns = 0;
-#endif
rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
rq->nr_integrity_segments = 0;
@@ -316,6 +309,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
rq->special = NULL;
/* tag was already set */
rq->extra_len = 0;
+ rq->__deadline = 0;
INIT_LIST_HEAD(&rq->timeout_list);
rq->timeout = 0;
@@ -324,6 +318,12 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
rq->end_io_data = NULL;
rq->next_rq = NULL;
+#ifdef CONFIG_BLK_CGROUP
+ rq->rl = NULL;
+ set_start_time_ns(rq);
+ rq->io_start_time_ns = 0;
+#endif
+
data->ctx->rq_dispatched[op_is_sync(op)]++;
return rq;
}
@@ -443,7 +443,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
blk_queue_exit(q);
return ERR_PTR(-EXDEV);
}
- cpu = cpumask_first(alloc_data.hctx->cpumask);
+ cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
alloc_data.ctx = __blk_mq_get_ctx(q, cpu);
rq = blk_mq_get_request(q, NULL, op, &alloc_data);
@@ -485,8 +485,7 @@ void blk_mq_free_request(struct request *rq)
if (blk_rq_rl(rq))
blk_put_rl(blk_rq_rl(rq));
- clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
- clear_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags);
+ 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)
@@ -532,6 +531,9 @@ static void __blk_mq_complete_request(struct request *rq)
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 (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq);
if (rq->rq_flags & RQF_STATS) {
@@ -559,6 +561,56 @@ static void __blk_mq_complete_request(struct request *rq)
put_cpu();
}
+static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
+ __releases(hctx->srcu)
+{
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+ rcu_read_unlock();
+ else
+ srcu_read_unlock(hctx->srcu, srcu_idx);
+}
+
+static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
+ __acquires(hctx->srcu)
+{
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+ /* shut up gcc false positive */
+ *srcu_idx = 0;
+ rcu_read_lock();
+ } else
+ *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
@@ -570,17 +622,33 @@ static void __blk_mq_complete_request(struct request *rq)
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)))
return;
- if (!blk_mark_rq_complete(rq))
+
+ /*
+ * 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);
}
EXPORT_SYMBOL(blk_mq_complete_request);
int blk_mq_request_started(struct request *rq)
{
- return test_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+ return blk_mq_rq_state(rq) != MQ_RQ_IDLE;
}
EXPORT_SYMBOL_GPL(blk_mq_request_started);
@@ -598,34 +666,27 @@ void blk_mq_start_request(struct request *rq)
wbt_issue(q->rq_wb, &rq->issue_stat);
}
- blk_add_timer(rq);
-
- WARN_ON_ONCE(test_bit(REQ_ATOM_STARTED, &rq->atomic_flags));
+ WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
/*
- * Mark us as started and clear complete. Complete might have been
- * set if requeue raced with timeout, which then marked it as
- * complete. So be sure to clear complete again when we start
- * the request, otherwise we'll ignore the completion event.
+ * 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.
*
- * Ensure that ->deadline is visible before we set STARTED, such that
- * blk_mq_check_expired() is guaranteed to observe our ->deadline when
- * it observes STARTED.
+ * 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.
*/
- smp_wmb();
- set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
- if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags)) {
- /*
- * Coherence order guarantees these consecutive stores to a
- * single variable propagate in the specified order. Thus the
- * clear_bit() is ordered _after_ the set bit. See
- * blk_mq_check_expired().
- *
- * (the bits must be part of the same byte for this to be
- * true).
- */
- clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
- }
+ preempt_disable();
+ write_seqcount_begin(&rq->gstate_seq);
+
+ blk_mq_rq_update_state(rq, MQ_RQ_IN_FLIGHT);
+ blk_add_timer(rq);
+
+ write_seqcount_end(&rq->gstate_seq);
+ preempt_enable();
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
@@ -639,13 +700,9 @@ void blk_mq_start_request(struct request *rq)
EXPORT_SYMBOL(blk_mq_start_request);
/*
- * When we reach here because queue is busy, REQ_ATOM_COMPLETE
- * flag isn't set yet, so there may be race with timeout handler,
- * but given rq->deadline is just set in .queue_rq() under
- * this situation, the race won't be possible in reality because
- * rq->timeout should be set as big enough to cover the window
- * between blk_mq_start_request() called from .queue_rq() and
- * clearing REQ_ATOM_STARTED here.
+ * 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)
{
@@ -657,7 +714,8 @@ static void __blk_mq_requeue_request(struct request *rq)
wbt_requeue(q->rq_wb, &rq->issue_stat);
blk_mq_sched_requeue_request(rq);
- if (test_and_clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) {
+ if (blk_mq_rq_state(rq) != MQ_RQ_IDLE) {
+ blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
if (q->dma_drain_size && blk_rq_bytes(rq))
rq->nr_phys_segments--;
}
@@ -689,13 +747,13 @@ static void blk_mq_requeue_work(struct work_struct *work)
rq->rq_flags &= ~RQF_SOFTBARRIER;
list_del_init(&rq->queuelist);
- blk_mq_sched_insert_request(rq, true, false, false, true);
+ blk_mq_sched_insert_request(rq, true, false, false);
}
while (!list_empty(&rq_list)) {
rq = list_entry(rq_list.next, struct request, queuelist);
list_del_init(&rq->queuelist);
- blk_mq_sched_insert_request(rq, false, false, false, true);
+ blk_mq_sched_insert_request(rq, false, false, false);
}
blk_mq_run_hw_queues(q, false);
@@ -729,7 +787,7 @@ EXPORT_SYMBOL(blk_mq_add_to_requeue_list);
void blk_mq_kick_requeue_list(struct request_queue *q)
{
- kblockd_schedule_delayed_work(&q->requeue_work, 0);
+ kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
}
EXPORT_SYMBOL(blk_mq_kick_requeue_list);
@@ -755,24 +813,15 @@ EXPORT_SYMBOL(blk_mq_tag_to_rq);
struct blk_mq_timeout_data {
unsigned long next;
unsigned int next_set;
+ unsigned int nr_expired;
};
-void blk_mq_rq_timed_out(struct request *req, bool reserved)
+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;
- /*
- * We know that complete is set at this point. If STARTED isn't set
- * anymore, then the request isn't active and the "timeout" should
- * just be ignored. This can happen due to the bitflag ordering.
- * Timeout first checks if STARTED is set, and if it is, assumes
- * the request is active. But if we race with completion, then
- * both flags will get cleared. So check here again, and ignore
- * a timeout event with a request that isn't active.
- */
- if (!test_bit(REQ_ATOM_STARTED, &req->atomic_flags))
- return;
+ req->rq_flags |= RQF_MQ_TIMEOUT_EXPIRED;
if (ops->timeout)
ret = ops->timeout(req, reserved);
@@ -782,8 +831,13 @@ void blk_mq_rq_timed_out(struct request *req, bool reserved)
__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);
- blk_clear_rq_complete(req);
break;
case BLK_EH_NOT_HANDLED:
break;
@@ -797,50 +851,51 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
struct request *rq, void *priv, bool reserved)
{
struct blk_mq_timeout_data *data = priv;
- unsigned long deadline;
+ unsigned long gstate, deadline;
+ int start;
- if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))
- return;
+ might_sleep();
- /*
- * Ensures that if we see STARTED we must also see our
- * up-to-date deadline, see blk_mq_start_request().
- */
- smp_rmb();
+ if (rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED)
+ return;
- deadline = READ_ONCE(rq->deadline);
+ /* 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();
+ }
- /*
- * The rq being checked may have been freed and reallocated
- * out already here, we avoid this race by checking rq->deadline
- * and REQ_ATOM_COMPLETE flag together:
- *
- * - if rq->deadline is observed as new value because of
- * reusing, the rq won't be timed out because of timing.
- * - if rq->deadline is observed as previous value,
- * REQ_ATOM_COMPLETE flag won't be cleared in reuse path
- * because we put a barrier between setting rq->deadline
- * and clearing the flag in blk_mq_start_request(), so
- * this rq won't be timed out too.
- */
- if (time_after_eq(jiffies, deadline)) {
- if (!blk_mark_rq_complete(rq)) {
- /*
- * Again coherence order ensures that consecutive reads
- * from the same variable must be in that order. This
- * ensures that if we see COMPLETE clear, we must then
- * see STARTED set and we'll ignore this timeout.
- *
- * (There's also the MB implied by the test_and_clear())
- */
- blk_mq_rq_timed_out(rq, reserved);
- }
+ /* 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;
}
}
+static void blk_mq_terminate_expired(struct blk_mq_hw_ctx *hctx,
+ struct request *rq, void *priv, bool reserved)
+{
+ /*
+ * 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.
+ */
+ if (!(rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED) &&
+ READ_ONCE(rq->gstate) == rq->aborted_gstate)
+ blk_mq_rq_timed_out(rq, reserved);
+}
+
static void blk_mq_timeout_work(struct work_struct *work)
{
struct request_queue *q =
@@ -848,7 +903,9 @@ static void blk_mq_timeout_work(struct work_struct *work)
struct blk_mq_timeout_data data = {
.next = 0,
.next_set = 0,
+ .nr_expired = 0,
};
+ struct blk_mq_hw_ctx *hctx;
int i;
/* A deadlock might occur if a request is stuck requiring a
@@ -867,14 +924,46 @@ static void blk_mq_timeout_work(struct work_struct *work)
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);
+ 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);
} else {
- struct blk_mq_hw_ctx *hctx;
-
+ /*
+ * Request timeouts are handled as a forward rolling timer. If
+ * we end up here it means that no requests are pending and
+ * also that no request has been pending for a while. Mark
+ * each hctx as idle.
+ */
queue_for_each_hw_ctx(q, hctx, i) {
/* the hctx may be unmapped, so check it here */
if (blk_mq_hw_queue_mapped(hctx))
@@ -1010,66 +1099,67 @@ static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
/*
* Mark us waiting for a tag. For shared tags, this involves hooking us into
- * the tag wakeups. For non-shared tags, we can simply mark us nedeing a
- * restart. For both caes, take care to check the condition again after
+ * the tag wakeups. For non-shared tags, we can simply mark us needing a
+ * restart. For both cases, take care to check the condition again after
* marking us as waiting.
*/
static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx **hctx,
struct request *rq)
{
struct blk_mq_hw_ctx *this_hctx = *hctx;
- bool shared_tags = (this_hctx->flags & BLK_MQ_F_TAG_SHARED) != 0;
struct sbq_wait_state *ws;
wait_queue_entry_t *wait;
bool ret;
- if (!shared_tags) {
+ if (!(this_hctx->flags & BLK_MQ_F_TAG_SHARED)) {
if (!test_bit(BLK_MQ_S_SCHED_RESTART, &this_hctx->state))
set_bit(BLK_MQ_S_SCHED_RESTART, &this_hctx->state);
- } else {
- wait = &this_hctx->dispatch_wait;
- if (!list_empty_careful(&wait->entry))
- return false;
- spin_lock(&this_hctx->lock);
- if (!list_empty(&wait->entry)) {
- spin_unlock(&this_hctx->lock);
- return false;
- }
+ /*
+ * It's possible that a tag was freed in the window between the
+ * allocation failure and adding the hardware queue to the wait
+ * queue.
+ *
+ * Don't clear RESTART here, someone else could have set it.
+ * At most this will cost an extra queue run.
+ */
+ return blk_mq_get_driver_tag(rq, hctx, false);
+ }
- ws = bt_wait_ptr(&this_hctx->tags->bitmap_tags, this_hctx);
- add_wait_queue(&ws->wait, wait);
+ wait = &this_hctx->dispatch_wait;
+ if (!list_empty_careful(&wait->entry))
+ return false;
+
+ spin_lock(&this_hctx->lock);
+ if (!list_empty(&wait->entry)) {
+ spin_unlock(&this_hctx->lock);
+ return false;
}
+ ws = bt_wait_ptr(&this_hctx->tags->bitmap_tags, this_hctx);
+ add_wait_queue(&ws->wait, wait);
+
/*
* It's possible that a tag was freed in the window between the
* allocation failure and adding the hardware queue to the wait
* queue.
*/
ret = blk_mq_get_driver_tag(rq, hctx, false);
-
- if (!shared_tags) {
- /*
- * Don't clear RESTART here, someone else could have set it.
- * At most this will cost an extra queue run.
- */
- return ret;
- } else {
- if (!ret) {
- spin_unlock(&this_hctx->lock);
- return false;
- }
-
- /*
- * We got a tag, remove ourselves from the wait queue to ensure
- * someone else gets the wakeup.
- */
- spin_lock_irq(&ws->wait.lock);
- list_del_init(&wait->entry);
- spin_unlock_irq(&ws->wait.lock);
+ if (!ret) {
spin_unlock(&this_hctx->lock);
- return true;
+ return false;
}
+
+ /*
+ * We got a tag, remove ourselves from the wait queue to ensure
+ * someone else gets the wakeup.
+ */
+ spin_lock_irq(&ws->wait.lock);
+ list_del_init(&wait->entry);
+ spin_unlock_irq(&ws->wait.lock);
+ spin_unlock(&this_hctx->lock);
+
+ return true;
}
bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list,
@@ -1206,9 +1296,27 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
/*
* We should be running this queue from one of the CPUs that
* are mapped to it.
+ *
+ * There are at least two related races now between setting
+ * hctx->next_cpu from blk_mq_hctx_next_cpu() and running
+ * __blk_mq_run_hw_queue():
+ *
+ * - hctx->next_cpu is found offline in blk_mq_hctx_next_cpu(),
+ * but later it becomes online, then this warning is harmless
+ * at all
+ *
+ * - hctx->next_cpu is found online in blk_mq_hctx_next_cpu(),
+ * but later it becomes offline, then the warning can't be
+ * triggered, and we depend on blk-mq timeout handler to
+ * handle dispatched requests to this hctx
*/
- WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
- cpu_online(hctx->next_cpu));
+ if (!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) &&
+ cpu_online(hctx->next_cpu)) {
+ printk(KERN_WARNING "run queue from wrong CPU %d, hctx %s\n",
+ raw_smp_processor_id(),
+ cpumask_empty(hctx->cpumask) ? "inactive": "active");
+ dump_stack();
+ }
/*
* We can't run the queue inline with ints disabled. Ensure that
@@ -1216,17 +1324,11 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
*/
WARN_ON_ONCE(in_interrupt());
- if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
- rcu_read_lock();
- blk_mq_sched_dispatch_requests(hctx);
- rcu_read_unlock();
- } else {
- might_sleep();
+ might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
- srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
- blk_mq_sched_dispatch_requests(hctx);
- srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
- }
+ hctx_lock(hctx, &srcu_idx);
+ blk_mq_sched_dispatch_requests(hctx);
+ hctx_unlock(hctx, srcu_idx);
}
/*
@@ -1237,20 +1339,47 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
*/
static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
{
+ bool tried = false;
+
if (hctx->queue->nr_hw_queues == 1)
return WORK_CPU_UNBOUND;
if (--hctx->next_cpu_batch <= 0) {
int next_cpu;
-
- next_cpu = cpumask_next(hctx->next_cpu, hctx->cpumask);
+select_cpu:
+ next_cpu = cpumask_next_and(hctx->next_cpu, hctx->cpumask,
+ cpu_online_mask);
if (next_cpu >= nr_cpu_ids)
- next_cpu = cpumask_first(hctx->cpumask);
+ next_cpu = cpumask_first_and(hctx->cpumask,cpu_online_mask);
- hctx->next_cpu = next_cpu;
+ /*
+ * No online CPU is found, so have to make sure hctx->next_cpu
+ * is set correctly for not breaking workqueue.
+ */
+ if (next_cpu >= nr_cpu_ids)
+ hctx->next_cpu = cpumask_first(hctx->cpumask);
+ else
+ hctx->next_cpu = next_cpu;
hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
}
+ /*
+ * Do unbound schedule if we can't find a online CPU for this hctx,
+ * and it should only happen in the path of handling CPU DEAD.
+ */
+ if (!cpu_online(hctx->next_cpu)) {
+ if (!tried) {
+ tried = true;
+ goto select_cpu;
+ }
+
+ /*
+ * Make sure to re-select CPU next time once after CPUs
+ * in hctx->cpumask become online again.
+ */
+ hctx->next_cpu_batch = 1;
+ return WORK_CPU_UNBOUND;
+ }
return hctx->next_cpu;
}
@@ -1274,9 +1403,8 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
put_cpu();
}
- kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
- &hctx->run_work,
- msecs_to_jiffies(msecs));
+ kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
+ msecs_to_jiffies(msecs));
}
void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
@@ -1287,7 +1415,23 @@ EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);
bool blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
{
- if (blk_mq_hctx_has_pending(hctx)) {
+ int srcu_idx;
+ bool need_run;
+
+ /*
+ * When queue is quiesced, we may be switching io scheduler, or
+ * updating nr_hw_queues, or other things, and we can't run queue
+ * any more, even __blk_mq_hctx_has_pending() can't be called safely.
+ *
+ * And queue will be rerun in blk_mq_unquiesce_queue() if it is
+ * quiesced.
+ */
+ hctx_lock(hctx, &srcu_idx);
+ need_run = !blk_queue_quiesced(hctx->queue) &&
+ blk_mq_hctx_has_pending(hctx);
+ hctx_unlock(hctx, srcu_idx);
+
+ if (need_run) {
__blk_mq_delay_run_hw_queue(hctx, async, 0);
return true;
}
@@ -1595,9 +1739,9 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true);
}
-static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
- struct request *rq,
- blk_qc_t *cookie, bool may_sleep)
+static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq,
+ blk_qc_t *cookie)
{
struct request_queue *q = rq->q;
struct blk_mq_queue_data bd = {
@@ -1606,15 +1750,52 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
};
blk_qc_t new_cookie;
blk_status_t ret;
+
+ new_cookie = request_to_qc_t(hctx, rq);
+
+ /*
+ * For OK queue, we are done. For error, caller may kill it.
+ * Any other error (busy), just add it to our list as we
+ * previously would have done.
+ */
+ ret = q->mq_ops->queue_rq(hctx, &bd);
+ switch (ret) {
+ case BLK_STS_OK:
+ *cookie = new_cookie;
+ break;
+ case BLK_STS_RESOURCE:
+ __blk_mq_requeue_request(rq);
+ break;
+ default:
+ *cookie = BLK_QC_T_NONE;
+ break;
+ }
+
+ return ret;
+}
+
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+ struct request *rq,
+ blk_qc_t *cookie,
+ bool bypass_insert)
+{
+ struct request_queue *q = rq->q;
bool run_queue = true;
- /* RCU or SRCU read lock is needed before checking quiesced flag */
+ /*
+ * RCU or SRCU read lock is needed before checking quiesced flag.
+ *
+ * When queue is stopped or quiesced, ignore 'bypass_insert' from
+ * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
+ * and avoid driver to try to dispatch again.
+ */
if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
run_queue = false;
+ bypass_insert = false;
goto insert;
}
- if (q->elevator)
+ if (q->elevator && !bypass_insert)
goto insert;
if (!blk_mq_get_driver_tag(rq, NULL, false))
@@ -1625,47 +1806,47 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
goto insert;
}
- new_cookie = request_to_qc_t(hctx, rq);
-
- /*
- * For OK queue, we are done. For error, kill it. Any other
- * error (busy), just add it to our list as we previously
- * would have done
- */
- ret = q->mq_ops->queue_rq(hctx, &bd);
- switch (ret) {
- case BLK_STS_OK:
- *cookie = new_cookie;
- return;
- case BLK_STS_RESOURCE:
- __blk_mq_requeue_request(rq);
- goto insert;
- default:
- *cookie = BLK_QC_T_NONE;
- blk_mq_end_request(rq, ret);
- return;
- }
-
+ return __blk_mq_issue_directly(hctx, rq, cookie);
insert:
- blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
+ if (bypass_insert)
+ return BLK_STS_RESOURCE;
+
+ blk_mq_sched_insert_request(rq, false, run_queue, false);
+ return BLK_STS_OK;
}
static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
struct request *rq, blk_qc_t *cookie)
{
- if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
- rcu_read_lock();
- __blk_mq_try_issue_directly(hctx, rq, cookie, false);
- rcu_read_unlock();
- } else {
- unsigned int srcu_idx;
+ blk_status_t ret;
+ int srcu_idx;
- might_sleep();
+ might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
- srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
- __blk_mq_try_issue_directly(hctx, rq, cookie, true);
- srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
- }
+ hctx_lock(hctx, &srcu_idx);
+
+ ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
+ if (ret == BLK_STS_RESOURCE)
+ blk_mq_sched_insert_request(rq, false, true, false);
+ else if (ret != BLK_STS_OK)
+ blk_mq_end_request(rq, ret);
+
+ hctx_unlock(hctx, srcu_idx);
+}
+
+blk_status_t blk_mq_request_issue_directly(struct request *rq)
+{
+ blk_status_t ret;
+ int srcu_idx;
+ blk_qc_t unused_cookie;
+ struct blk_mq_ctx *ctx = rq->mq_ctx;
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(rq->q, ctx->cpu);
+
+ hctx_lock(hctx, &srcu_idx);
+ ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true);
+ hctx_unlock(hctx, srcu_idx);
+
+ return ret;
}
static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
@@ -1776,7 +1957,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
} else if (q->elevator) {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
- blk_mq_sched_insert_request(rq, false, true, true, true);
+ blk_mq_sched_insert_request(rq, false, true, true);
} else {
blk_mq_put_ctx(data.ctx);
blk_mq_bio_to_request(rq, bio);
@@ -1869,6 +2050,22 @@ static size_t order_to_size(unsigned int order)
return (size_t)PAGE_SIZE << order;
}
+static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
+ unsigned int hctx_idx, int node)
+{
+ int ret;
+
+ if (set->ops->init_request) {
+ ret = set->ops->init_request(set, rq, hctx_idx, node);
+ if (ret)
+ return ret;
+ }
+
+ seqcount_init(&rq->gstate_seq);
+ u64_stats_init(&rq->aborted_gstate_sync);
+ return 0;
+}
+
int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
unsigned int hctx_idx, unsigned int depth)
{
@@ -1930,12 +2127,9 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
struct request *rq = p;
tags->static_rqs[i] = rq;
- if (set->ops->init_request) {
- if (set->ops->init_request(set, rq, hctx_idx,
- node)) {
- tags->static_rqs[i] = NULL;
- goto fail;
- }
+ if (blk_mq_init_request(set, rq, hctx_idx, node)) {
+ tags->static_rqs[i] = NULL;
+ goto fail;
}
p += rq_size;
@@ -1994,7 +2188,8 @@ static void blk_mq_exit_hctx(struct request_queue *q,
{
blk_mq_debugfs_unregister_hctx(hctx);
- blk_mq_tag_idle(hctx);
+ if (blk_mq_hw_queue_mapped(hctx))
+ blk_mq_tag_idle(hctx);
if (set->ops->exit_request)
set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);
@@ -2005,7 +2200,7 @@ static void blk_mq_exit_hctx(struct request_queue *q,
set->ops->exit_hctx(hctx, hctx_idx);
if (hctx->flags & BLK_MQ_F_BLOCKING)
- cleanup_srcu_struct(hctx->queue_rq_srcu);
+ cleanup_srcu_struct(hctx->srcu);
blk_mq_remove_cpuhp(hctx);
blk_free_flush_queue(hctx->fq);
@@ -2074,13 +2269,11 @@ static int blk_mq_init_hctx(struct request_queue *q,
if (!hctx->fq)
goto sched_exit_hctx;
- if (set->ops->init_request &&
- set->ops->init_request(set, hctx->fq->flush_rq, hctx_idx,
- node))
+ if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx, node))
goto free_fq;
if (hctx->flags & BLK_MQ_F_BLOCKING)
- init_srcu_struct(hctx->queue_rq_srcu);
+ init_srcu_struct(hctx->srcu);
blk_mq_debugfs_register_hctx(q, hctx);
@@ -2116,16 +2309,11 @@ static void blk_mq_init_cpu_queues(struct request_queue *q,
INIT_LIST_HEAD(&__ctx->rq_list);
__ctx->queue = q;
- /* If the cpu isn't present, the cpu is mapped to first hctx */
- if (!cpu_present(i))
- continue;
-
- hctx = blk_mq_map_queue(q, i);
-
/*
* Set local node, IFF we have more than one hw queue. If
* not, we remain on the home node of the device
*/
+ hctx = blk_mq_map_queue(q, i);
if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
hctx->numa_node = local_memory_node(cpu_to_node(i));
}
@@ -2182,7 +2370,7 @@ static void blk_mq_map_swqueue(struct request_queue *q)
*
* If the cpu isn't present, the cpu is mapped to first hctx.
*/
- for_each_present_cpu(i) {
+ for_each_possible_cpu(i) {
hctx_idx = q->mq_map[i];
/* unmapped hw queue can be remapped after CPU topo changed */
if (!set->tags[hctx_idx] &&
@@ -2236,7 +2424,8 @@ static void blk_mq_map_swqueue(struct request_queue *q)
/*
* Initialize batch roundrobin counts
*/
- hctx->next_cpu = cpumask_first(hctx->cpumask);
+ hctx->next_cpu = cpumask_first_and(hctx->cpumask,
+ cpu_online_mask);
hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
}
}
@@ -2369,7 +2558,7 @@ static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
{
int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);
- BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, queue_rq_srcu),
+ BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
__alignof__(struct blk_mq_hw_ctx)) !=
sizeof(struct blk_mq_hw_ctx));
@@ -2386,6 +2575,9 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;
blk_mq_sysfs_unregister(q);
+
+ /* protect against switching io scheduler */
+ mutex_lock(&q->sysfs_lock);
for (i = 0; i < set->nr_hw_queues; i++) {
int node;
@@ -2430,6 +2622,7 @@ static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
}
}
q->nr_hw_queues = i;
+ mutex_unlock(&q->sysfs_lock);
blk_mq_sysfs_register(q);
}
@@ -2601,9 +2794,27 @@ static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
{
- if (set->ops->map_queues)
+ if (set->ops->map_queues) {
+ int cpu;
+ /*
+ * transport .map_queues is usually done in the following
+ * way:
+ *
+ * for (queue = 0; queue < set->nr_hw_queues; queue++) {
+ * mask = get_cpu_mask(queue)
+ * for_each_cpu(cpu, mask)
+ * set->mq_map[cpu] = queue;
+ * }
+ *
+ * When we need to remap, the table has to be cleared for
+ * killing stale mapping since one CPU may not be mapped
+ * to any hw queue.
+ */
+ for_each_possible_cpu(cpu)
+ set->mq_map[cpu] = 0;
+
return set->ops->map_queues(set);
- else
+ } else
return blk_mq_map_queues(set);
}
@@ -2712,6 +2923,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
return -EINVAL;
blk_mq_freeze_queue(q);
+ blk_mq_quiesce_queue(q);
ret = 0;
queue_for_each_hw_ctx(q, hctx, i) {
@@ -2735,6 +2947,7 @@ int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
if (!ret)
q->nr_requests = nr;
+ blk_mq_unquiesce_queue(q);
blk_mq_unfreeze_queue(q);
return ret;
@@ -2850,7 +3063,7 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
unsigned int nsecs;
ktime_t kt;
- if (test_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags))
+ if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
return false;
/*
@@ -2870,7 +3083,7 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
if (!nsecs)
return false;
- set_bit(REQ_ATOM_POLL_SLEPT, &rq->atomic_flags);
+ rq->rq_flags |= RQF_MQ_POLL_SLEPT;
/*
* This will be replaced with the stats tracking code, using
@@ -2884,7 +3097,7 @@ static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
hrtimer_init_sleeper(&hs, current);
do {
- if (test_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags))
+ if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
break;
set_current_state(TASK_UNINTERRUPTIBLE);
hrtimer_start_expires(&hs.timer, mode);
@@ -2970,12 +3183,6 @@ static bool blk_mq_poll(struct request_queue *q, blk_qc_t cookie)
static int __init blk_mq_init(void)
{
- /*
- * See comment in block/blk.h rq_atomic_flags enum
- */
- BUILD_BUG_ON((REQ_ATOM_STARTED / BITS_PER_BYTE) !=
- (REQ_ATOM_COMPLETE / BITS_PER_BYTE));
-
cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
blk_mq_hctx_notify_dead);
return 0;