@@ -198,6 +198,9 @@ void blk_rq_init(struct request_queue *q, struct request *rq)
rq->internal_tag = -1;
rq->start_time_ns = ktime_get_ns();
rq->part = NULL;
+#ifndef CONFIG_64BIT
+ seqcount_init(&rq->deadline_seq);
+#endif
}
EXPORT_SYMBOL(blk_rq_init);
@@ -335,8 +335,9 @@ static const char *const rqf_name[] = {
static const char *const blk_mq_rq_state_name_array[] = {
[MQ_RQ_IDLE] = "idle",
- [MQ_RQ_IN_FLIGHT] = "in_flight",
+ [MQ_RQ_IN_FLIGHT] = "in flight",
[MQ_RQ_COMPLETE] = "complete",
+ [MQ_RQ_TIMED_OUT] = "timed out",
};
static const char *blk_mq_rq_state_name(enum mq_rq_state rq_state)
@@ -6,6 +6,7 @@
*/
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/atomic.h> /* cmpxchg() */
#include <linux/backing-dev.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
@@ -322,6 +323,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
INIT_LIST_HEAD(&rq->timeout_list);
rq->timeout = 0;
+ WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
rq->end_io = NULL;
rq->end_io_data = NULL;
@@ -332,7 +334,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
#endif
data->ctx->rq_dispatched[op_is_sync(op)]++;
- refcount_set(&rq->ref, 1);
return rq;
}
@@ -466,19 +467,42 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
}
EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
-static void __blk_mq_free_request(struct request *rq)
+/**
+ * blk_mq_change_rq_state - atomically test and set request state
+ * @rq: Request pointer.
+ * @old_state: Old request state.
+ * @new_state: New request state.
+ *
+ * Returns %true if and only if the old state was @old and if the state has
+ * been changed into @new.
+ */
+static bool blk_mq_change_rq_state(struct request *rq,
+ enum mq_rq_state old_state,
+ enum mq_rq_state new_state)
{
- 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;
+ union blk_generation_and_state old_val = READ_ONCE(rq->gstate);
+ union blk_generation_and_state new_val = old_val;
- 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);
+ old_val.state = old_state;
+ new_val.state = new_state;
+ if (new_state == MQ_RQ_IN_FLIGHT)
+ new_val.generation++;
+ /*
+ * For transitions from state in-flight or timed out to another state
+ * cmpxchg() must be used. For other state transitions it is safe to
+ * use WRITE_ONCE().
+ */
+ switch (old_state) {
+ case MQ_RQ_IN_FLIGHT:
+ case MQ_RQ_TIMED_OUT:
+ WRITE_ONCE(rq->gstate.val, new_val.val);
+ return true;
+ case MQ_RQ_IDLE:
+ case MQ_RQ_COMPLETE:
+ return blk_mq_set_rq_state(rq, old_val, new_val);
+ }
+ WARN(true, "Invalid request state %d\n", old_state);
+ return false;
}
void blk_mq_free_request(struct request *rq)
@@ -487,6 +511,7 @@ void blk_mq_free_request(struct request *rq)
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)
@@ -509,9 +534,14 @@ void blk_mq_free_request(struct request *rq)
if (blk_rq_rl(rq))
blk_put_rl(blk_rq_rl(rq));
- WRITE_ONCE(rq->state, MQ_RQ_IDLE);
- if (refcount_dec_and_test(&rq->ref))
- __blk_mq_free_request(rq);
+ if (!blk_mq_change_rq_state(rq, blk_mq_rq_state(rq), MQ_RQ_IDLE))
+ WARN_ON_ONCE(true);
+ 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);
}
EXPORT_SYMBOL_GPL(blk_mq_free_request);
@@ -558,8 +588,8 @@ static void __blk_mq_complete_request(struct request *rq)
bool shared = false;
int cpu;
- if (!blk_mq_mark_complete(rq))
- return;
+ WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_COMPLETE);
+
if (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq);
@@ -615,7 +645,18 @@ void blk_mq_complete_request(struct request *rq)
{
if (unlikely(blk_should_fake_timeout(rq->q)))
return;
- __blk_mq_complete_request(rq);
+again:
+ if (blk_mq_change_rq_state(rq, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE)) {
+ __blk_mq_complete_request(rq);
+ return;
+ }
+ if (blk_mq_change_rq_state(rq, MQ_RQ_TIMED_OUT, MQ_RQ_COMPLETE))
+ return;
+ if (WARN_ON_ONCE(blk_mq_rq_state(rq) == MQ_RQ_IDLE ||
+ blk_mq_rq_state(rq) == MQ_RQ_COMPLETE))
+ return;
+ /* In the unlikely case of a race with the timeout code, retry. */
+ goto again;
}
EXPORT_SYMBOL(blk_mq_complete_request);
@@ -645,7 +686,7 @@ void blk_mq_start_request(struct request *rq)
WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);
blk_mq_add_timer(rq);
- WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);
+ WARN_ON_ONCE(!blk_mq_change_rq_state(rq, MQ_RQ_IDLE, MQ_RQ_IN_FLIGHT));
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
@@ -658,23 +699,46 @@ void blk_mq_start_request(struct request *rq)
}
EXPORT_SYMBOL(blk_mq_start_request);
+/**
+ * __blk_mq_requeue_request - requeue a request
+ * @rq: request to be requeued
+ *
+ * This function is either called by blk_mq_requeue_request() or by the block
+ * layer core if .queue_rq() returned BLK_STS_RESOURCE or BLK_STS_DEV_RESOURCE.
+ * If the request state is MQ_RQ_IN_FLIGHT and if this function is called from
+ * inside .queue_rq() then it is guaranteed that the timeout code won't try to
+ * modify the request state while this function is in progress because an RCU
+ * read lock is held around .queue_rq() and because the timeout code calls
+ * synchronize_rcu() after having marked requests and before processing
+ * time-outs.
+ */
static void __blk_mq_requeue_request(struct request *rq)
{
struct request_queue *q = rq->q;
+ enum mq_rq_state old_state = blk_mq_rq_state(rq);
blk_mq_put_driver_tag(rq);
trace_block_rq_requeue(q, rq);
rq_qos_requeue(q, rq);
- if (blk_mq_request_started(rq)) {
- WRITE_ONCE(rq->state, MQ_RQ_IDLE);
- rq->rq_flags &= ~RQF_TIMED_OUT;
+ if (old_state != MQ_RQ_IDLE) {
+ if (!blk_mq_change_rq_state(rq, old_state, MQ_RQ_IDLE))
+ WARN_ON_ONCE(true);
if (q->dma_drain_size && blk_rq_bytes(rq))
rq->nr_phys_segments--;
}
}
+/**
+ * blk_mq_requeue_request - requeue a request
+ * @rq: request to be requeued
+ * @kick_requeue_list: whether or not to kick the requeue_list
+ *
+ * This function is called after a request has completed, after a request has
+ * timed out or from inside .queue_rq(). In the latter case the request may
+ * already have been started.
+ */
void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
{
__blk_mq_requeue_request(rq);
@@ -767,82 +831,117 @@ struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
}
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)
{
- req->rq_flags |= RQF_TIMED_OUT;
- if (req->q->mq_ops->timeout) {
- enum blk_eh_timer_return ret;
+ enum blk_eh_timer_return ret;
- ret = req->q->mq_ops->timeout(req, reserved);
- if (ret == BLK_EH_DONT_RESET_TIMER)
- return;
- WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
+ if (!req->q->mq_ops->timeout) {
+ blk_mq_add_timer(req);
+ return;
}
+ ret = req->q->mq_ops->timeout(req, reserved);
+ /*
+ * BLK_EH_DONT_RESET_TIMER means that the block driver either
+ * completed the request or still owns the request and will
+ * continue processing the timeout asynchronously. In the
+ * latter case, if blk_mq_complete_request() was called while
+ * the timeout handler was in progress, ignore that call.
+ */
+ if (ret == BLK_EH_DONT_RESET_TIMER)
+ return;
+ WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
blk_mq_add_timer(req);
+again:
+ if (blk_mq_change_rq_state(req, MQ_RQ_TIMED_OUT, MQ_RQ_IN_FLIGHT))
+ return;
+ if (blk_mq_rq_state(req) == MQ_RQ_COMPLETE) {
+ __blk_mq_complete_request(req);
+ return;
+ }
+ if (WARN_ON_ONCE(blk_mq_rq_state(req) == MQ_RQ_IDLE ||
+ blk_mq_rq_state(req) == MQ_RQ_IN_FLIGHT))
+ return;
+ /*
+ * In the unlikely case of a race with the request completion code,
+ * retry.
+ */
+ goto again;
}
-static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
+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;
+ union blk_generation_and_state gstate = READ_ONCE(rq->gstate);
unsigned long deadline;
- if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
- return false;
- if (rq->rq_flags & RQF_TIMED_OUT)
- return false;
+ might_sleep();
- deadline = blk_rq_deadline(rq);
- if (time_after_eq(jiffies, deadline))
- return true;
+#ifdef CONFIG_64BIT
+ deadline = rq->__deadline;
+#else
+ while (true) {
+ int start;
- if (*next == 0)
- *next = deadline;
- else if (time_after(*next, deadline))
- *next = deadline;
- return false;
+ start = read_seqcount_begin(&rq->deadline_seq);
+ deadline = rq->__deadline;
+ if (!read_seqcount_retry(&rq->deadline_seq, start))
+ break;
+ cond_resched();
+ }
+#endif
+
+ /*
+ * Make sure that rq->aborted_gstate != rq->gstate if a request gets
+ * recycled before blk_mq_terminate_expired() is called.
+ */
+ rq->aborted_gstate = gstate;
+ rq->aborted_gstate.generation ^= (1UL << 29);
+ if (gstate.state == MQ_RQ_IN_FLIGHT &&
+ time_after_eq(jiffies, deadline)) {
+ /* request timed out */
+ rq->aborted_gstate = 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_check_expired(struct blk_mq_hw_ctx *hctx,
+static void blk_mq_terminate_expired(struct blk_mq_hw_ctx *hctx,
struct request *rq, void *priv, bool reserved)
{
- unsigned long *next = priv;
+ union blk_generation_and_state old_val = rq->aborted_gstate;
+ union blk_generation_and_state new_val = old_val;
- /*
- * 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;
+ new_val.state = MQ_RQ_TIMED_OUT;
/*
- * 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.
+ * We marked @rq->aborted_gstate and waited for ongoing .queue_rq()
+ * calls. If rq->gstate has not changed that means that it
+ * is now safe to change the request state and to handle the timeout.
*/
- if (blk_mq_req_expired(rq, next))
+ if (blk_mq_set_rq_state(rq, old_val, new_val))
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);
- unsigned long next = 0;
+ struct blk_mq_timeout_data data = {
+ .next = 0,
+ .next_set = 0,
+ .nr_expired = 0,
+ };
struct blk_mq_hw_ctx *hctx;
int i;
@@ -862,10 +961,41 @@ static void blk_mq_timeout_work(struct work_struct *work)
if (!percpu_ref_tryget(&q->q_usage_counter))
return;
- blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);
+ /* 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;
+
+ /*
+ * For very short timeouts it can happen that
+ * blk_mq_check_expired() modifies the state of a request
+ * while .queue_rq() is still in progress. Hence wait until
+ * these .queue_rq() calls have finished. This is also
+ * necessary to avoid races with blk_mq_requeue_request() for
+ * requests that have already been started.
+ */
+ 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);
- if (next != 0) {
- mod_timer(&q->timeout, next);
+ 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 {
/*
* Request timeouts are handled as a forward rolling timer. If
@@ -2009,7 +2139,9 @@ static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
return ret;
}
- WRITE_ONCE(rq->state, MQ_RQ_IDLE);
+#ifndef CONFIG_64BIT
+ seqcount_init(&rq->deadline_seq);
+#endif
return 0;
}
@@ -90,13 +90,21 @@ extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
void blk_mq_release(struct request_queue *q);
+static inline bool blk_mq_set_rq_state(struct request *rq,
+ union blk_generation_and_state old_val,
+ union blk_generation_and_state new_val)
+{
+ return cmpxchg(&rq->gstate.val, old_val.val, new_val.val) ==
+ old_val.val;
+}
+
/**
* blk_mq_rq_state() - read the current MQ_RQ_* state of a request
* @rq: target request.
*/
static inline enum mq_rq_state blk_mq_rq_state(struct request *rq)
{
- return READ_ONCE(rq->state);
+ return READ_ONCE(rq->gstate).state;
}
static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
@@ -142,6 +142,22 @@ void blk_timeout_work(struct work_struct *work)
spin_unlock_irqrestore(q->queue_lock, flags);
}
+/* Update deadline to @time. May be called from interrupt context. */
+static void blk_mq_rq_set_deadline(struct request *rq, unsigned long new_time)
+{
+#ifdef CONFIG_64BIT
+ rq->__deadline = new_time;
+#else
+ unsigned long flags;
+
+ local_irq_save(flags);
+ write_seqcount_begin(&rq->deadline_seq);
+ rq->__deadline = new_time;
+ write_seqcount_end(&rq->deadline_seq);
+ local_irq_restore(flags);
+#endif
+}
+
/**
* blk_abort_request -- Request request recovery for the specified command
* @req: pointer to the request of interest
@@ -155,11 +171,10 @@ void blk_abort_request(struct request *req)
{
if (req->q->mq_ops) {
/*
- * All we need to ensure is that timeout scan takes place
- * immediately and that scan sees the new timeout value.
- * No need for fancy synchronizations.
+ * Ensure that a timeout scan takes place immediately and that
+ * that scan sees the new timeout value.
*/
- blk_rq_set_deadline(req, jiffies);
+ blk_mq_rq_set_deadline(req, jiffies);
kblockd_schedule_work(&req->q->timeout_work);
} else {
if (blk_mark_rq_complete(req))
@@ -228,7 +243,6 @@ void blk_add_timer(struct request *req)
if (!req->timeout)
req->timeout = q->rq_timeout;
- req->rq_flags &= ~RQF_TIMED_OUT;
deadline = jiffies + req->timeout;
blk_rq_set_deadline(req, deadline);
list_add_tail(&req->timeout_list, &req->q->timeout_list);
@@ -250,9 +264,7 @@ void blk_mq_add_timer(struct request *req)
if (!req->timeout)
req->timeout = q->rq_timeout;
-
- req->rq_flags &= ~RQF_TIMED_OUT;
deadline = jiffies + req->timeout;
- blk_rq_set_deadline(req, deadline);
+ blk_mq_rq_set_deadline(req, deadline);
__blk_add_timer(req, deadline);
}
@@ -296,20 +296,6 @@ enum blk_eh_timer_return scsi_times_out(struct request *req)
rtn = host->hostt->eh_timed_out(scmd);
if (rtn == BLK_EH_DONT_RESET_TIMER) {
- /*
- * For blk-mq, we must set the request state to complete now
- * before sending the request to the scsi error handler. This
- * will prevent a use-after-free in the event the LLD manages
- * to complete the request before the error handler finishes
- * processing this timed out request.
- *
- * If the request was already completed, then the LLD beat the
- * time out handler from transferring the request to the scsi
- * error handler. In that case we can return immediately as no
- * further action is required.
- */
- if (req->q->mq_ops && !blk_mq_mark_complete(req))
- return rtn;
if (scsi_abort_command(scmd) != SUCCESS) {
set_host_byte(scmd, DID_TIME_OUT);
scsi_eh_scmd_add(scmd);
@@ -289,20 +289,6 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues);
void blk_mq_quiesce_queue_nowait(struct request_queue *q);
-/**
- * blk_mq_mark_complete() - Set request state to complete
- * @rq: request to set to complete state
- *
- * Returns true if request state was successfully set to complete. If
- * successful, the caller is responsibile for seeing this request is ended, as
- * blk_mq_complete_request will not work again.
- */
-static inline bool blk_mq_mark_complete(struct request *rq)
-{
- return cmpxchg(&rq->state, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE) ==
- MQ_RQ_IN_FLIGHT;
-}
-
/*
* Driver command data is immediately after the request. So subtract request
* size to get back to the original request, add request size to get the PDU.
@@ -126,20 +126,39 @@ typedef __u32 __bitwise req_flags_t;
#define RQF_ZONE_WRITE_LOCKED ((__force req_flags_t)(1 << 19))
/* already slept for hybrid poll */
#define RQF_MQ_POLL_SLEPT ((__force req_flags_t)(1 << 20))
-/* ->timeout has been called, don't expire again */
-#define RQF_TIMED_OUT ((__force req_flags_t)(1 << 21))
/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \
(RQF_STARTED | RQF_SOFTBARRIER | RQF_FLUSH_SEQ | RQF_SPECIAL_PAYLOAD)
-/*
- * Request state for blk-mq.
+union blk_generation_and_state {
+ struct {
+ uint32_t generation:30;
+ uint32_t state:2;
+ };
+ uint32_t val;
+};
+
+/**
+ * enum mq_rq_state - blk-mq request state
+ *
+ * The legal state transitions are:
+ * - idle -> in flight: blk_mq_start_request()
+ * - in flight -> complete: blk_mq_complete_request()
+ * - timed out -> complete: blk_mq_complete_request()
+ * - in flight -> timed out: request times out
+ * - complete -> idle: blk_mq_requeue_request() or blk_mq_free_request()
+ * - in flight -> idle: blk_mq_requeue_request() or blk_mq_free_request()
+ * - timed out -> idle: blk_mq_requeue_request() or blk_mq_free_request()
+ * - timed out -> in flight: request restart due to BLK_EH_RESET_TIMER
+ *
+ * See also blk_generation_and_state.state.
*/
enum mq_rq_state {
MQ_RQ_IDLE = 0,
MQ_RQ_IN_FLIGHT = 1,
MQ_RQ_COMPLETE = 2,
+ MQ_RQ_TIMED_OUT = 3,
};
/*
@@ -242,12 +261,26 @@ struct request {
unsigned int extra_len; /* length of alignment and padding */
- enum mq_rq_state state;
- refcount_t ref;
-
unsigned int timeout;
- /* access through blk_rq_set_deadline, blk_rq_deadline */
+ /*
+ * ->aborted_gstate is used by the timeout to claim a specific
+ * recycle instance of this request. See blk_mq_timeout_work().
+ */
+ union blk_generation_and_state aborted_gstate;
+
+ /*
+ * Access through blk_rq_deadline() and blk_rq_set_deadline(),
+ * blk_mark_rq_complete(), blk_clear_rq_complete() and
+ * blk_rq_is_complete() for legacy queues or blk_mq_rq_state(),
+ * blk_mq_change_rq_state() and blk_mq_rq_set_deadline() for
+ * blk-mq queues. deadline_seq protects __deadline in blk-mq mode
+ * only.
+ */
+ union blk_generation_and_state gstate;
+#ifndef CONFIG_64BIT
+ seqcount_t deadline_seq;
+#endif
unsigned long __deadline;
struct list_head timeout_list;
Recently the blk-mq timeout handling code was reworked to avoid that completions that occur while a timeout handler is in progress get ignored. However, that rework removed the protection against completions that occur while a timeout handler is in progress. Fix this by introducing a new request state, namely MQ_RQ_TIMED_OUT. This state means that the timeout handler is in progress. Other changes in this patch are: - Reintroduce the request generation number to avoid that request timeout handling happens after a request has already completed. - Reintroduce deadline_seq to make reads and updates of the request deadline possible without having to use atomic instructions. - Remove the request state information that became superfluous due to this patch, namely the RQF_TIMED_OUT flag and the ref member. - Atomic instructions are only used to update the request state if a concurrent request state change could be in progress. - Move the code for managing the request state back from the SCSI core into the block layer core. This patch reverts the following two commits: * 0fc09f920983 ("blk-mq: export setting request completion state") * 065990bd198e ("scsi: set timed out out mq requests to complete") Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Cc: Martin K. Petersen <martin.petersen@oracle.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Keith Busch <keith.busch@intel.com> Cc: Jianchao Wang <jianchao.w.wang@oracle.com> Cc: Ming Lei <ming.lei@redhat.com> --- block/blk-core.c | 3 + block/blk-mq-debugfs.c | 3 +- block/blk-mq.c | 280 ++++++++++++++++++++++++++++---------- block/blk-mq.h | 10 +- block/blk-timeout.c | 28 ++-- drivers/scsi/scsi_error.c | 14 -- include/linux/blk-mq.h | 14 -- include/linux/blkdev.h | 49 +++++-- 8 files changed, 281 insertions(+), 120 deletions(-)