On Mon, Apr 09, 2018 at 06:34:55PM -0700, Bart Van Assche wrote:
> If a completion occurs after blk_mq_rq_timed_out() has reset
> rq->aborted_gstate and the request is again in flight when the timeout
> expires then a request will be completed twice: a first time by the
> timeout handler and a second time when the regular completion occurs.
>
> Additionally, the blk-mq timeout handling code ignores completions that
> occur after blk_mq_check_expired() has been called and before
> blk_mq_rq_timed_out() has reset rq->aborted_gstate. If a block driver
> timeout handler always returns BLK_EH_RESET_TIMER then the result will
> be that the request never terminates.
>
> Since the request state can be updated from two different contexts,
> namely regular completion and request timeout, this race cannot be
> fixed with RCU synchronization only. Fix this race as follows:
> - Split __deadline in two variables, namely lq_deadline for legacy
> request queues and mq_deadline for blk-mq request queues. Use atomic
> operations to update mq_deadline.
I don't think we need the atomic_long_cmpxchg, and can do with a plain
cmpxhg. Also unterminated cmpxchg loops are a bad idea, but I think
both callers are protected from other changes so we can turn that
into a WARN_ON(). That plus some minor cleanups in the version below,
only boot tested:
diff --git a/block/blk-core.c b/block/blk-core.c
index abcb8684ba67..7e88e4a9133d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -199,8 +199,6 @@ void blk_rq_init(struct request_queue *q, struct request
*rq)
rq->start_time = jiffies;
set_start_time_ns(rq);
rq->part = NULL;
- seqcount_init(&rq->gstate_seq);
- u64_stats_init(&rq->aborted_gstate_sync);
}
EXPORT_SYMBOL(blk_rq_init);
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 58b3b79cbe83..ecb934bafb29 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -345,7 +345,6 @@ static const char *const rqf_name[] = {
RQF_NAME(STATS),
RQF_NAME(SPECIAL_PAYLOAD),
RQF_NAME(ZONE_WRITE_LOCKED),
- RQF_NAME(MQ_TIMEOUT_EXPIRED),
RQF_NAME(MQ_POLL_SLEPT),
};
#undef RQF_NAME
diff --git a/block/blk-mq.c b/block/blk-mq.c
index f5c7dbcb954f..0f5c56789fde 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -477,7 +477,9 @@ void blk_mq_free_request(struct request *rq)
if (blk_rq_rl(rq))
blk_put_rl(blk_rq_rl(rq));
- blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
+ if (!blk_mq_change_rq_state(rq, blk_mq_rq_state(rq), MQ_RQ_IDLE))
+ WARN_ON_ONCE(1);
+
if (rq->tag != -1)
blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
if (sched_tag != -1)
@@ -523,8 +525,7 @@ 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);
+ WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_COMPLETE);
if (rq->internal_tag != -1)
blk_mq_sched_completed_request(rq);
@@ -573,36 +574,6 @@ static void hctx_lock(struct blk_mq_hw_ctx *hctx, int
*srcu_idx)
*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
@@ -614,27 +585,12 @@ static u64 blk_mq_rq_aborted_gstate(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 @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)
+ if (blk_mq_change_rq_state(rq, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE))
__blk_mq_complete_request(rq);
- hctx_unlock(hctx, srcu_idx);
}
EXPORT_SYMBOL(blk_mq_complete_request);
@@ -658,27 +614,7 @@ void blk_mq_start_request(struct request *rq)
wbt_issue(q->rq_wb, &rq->issue_stat);
}
- 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_mq_rq_update_state(rq, MQ_RQ_IN_FLIGHT);
- blk_add_timer(rq);
-
- write_seqcount_end(&rq->gstate_seq);
- preempt_enable();
+ blk_mq_add_timer(rq, MQ_RQ_IDLE, MQ_RQ_IN_FLIGHT);
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
@@ -691,22 +627,19 @@ void blk_mq_start_request(struct request *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;
+ unsigned long old_state = blk_mq_rq_state(rq);
blk_mq_put_driver_tag(rq);
trace_block_rq_requeue(q, rq);
wbt_requeue(q->rq_wb, &rq->issue_stat);
- if (blk_mq_rq_state(rq) != MQ_RQ_IDLE) {
- blk_mq_rq_update_state(rq, MQ_RQ_IDLE);
+ if (old_state != MQ_RQ_IDLE) {
+ if (!blk_mq_change_rq_state(rq, old_state, MQ_RQ_IDLE))
+ WARN_ON_ONCE(1);
if (q->dma_drain_size && blk_rq_bytes(rq))
rq->nr_phys_segments--;
}
@@ -807,7 +740,6 @@ 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)
@@ -815,8 +747,6 @@ 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);
@@ -825,13 +755,7 @@ static 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_mq_add_timer(req, MQ_RQ_COMPLETE, MQ_RQ_IN_FLIGHT);
break;
case BLK_EH_NOT_HANDLED:
break;
@@ -845,60 +769,23 @@ 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 gstate, deadline;
- int start;
-
- might_sleep();
-
- if (rq->rq_flags & RQF_MQ_TIMEOUT_EXPIRED)
- return;
-
- /* 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();
- }
+ unsigned long deadline = blk_rq_deadline(rq);
- /* 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++;
+ if (time_after_eq(jiffies, deadline) &&
+ blk_mq_change_rq_state(rq, MQ_RQ_IN_FLIGHT, MQ_RQ_COMPLETE)) {
+ blk_mq_rq_timed_out(rq, reserved);
} 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 =
container_of(work, struct request_queue, timeout_work);
- struct blk_mq_timeout_data data = {
- .next = 0,
- .next_set = 0,
- .nr_expired = 0,
- };
+ struct blk_mq_timeout_data data = { };
struct blk_mq_hw_ctx *hctx;
int i;
@@ -921,33 +808,6 @@ static void blk_mq_timeout_work(struct work_struct *work)
/* 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);
@@ -2067,8 +1927,6 @@ static int blk_mq_init_request(struct blk_mq_tag_set
*set, struct request *rq,
return ret;
}
- seqcount_init(&rq->gstate_seq);
- u64_stats_init(&rq->aborted_gstate_sync);
return 0;
}
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 88c558f71819..a9805b9809c4 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -27,18 +27,11 @@ struct blk_mq_ctx {
struct kobject kobj;
} ____cacheline_aligned_in_smp;
-/*
- * Bits for request->gstate. The lower two bits carry MQ_RQ_* state value
- * and the upper bits the generation number.
- */
+/* Lowest two bits of request->__deadline. */
enum mq_rq_state {
MQ_RQ_IDLE = 0,
MQ_RQ_IN_FLIGHT = 1,
MQ_RQ_COMPLETE = 2,
-
- MQ_RQ_STATE_BITS = 2,
- MQ_RQ_STATE_MASK = (1 << MQ_RQ_STATE_BITS) - 1,
- MQ_RQ_GEN_INC = 1 << MQ_RQ_STATE_BITS,
};
void blk_mq_freeze_queue(struct request_queue *q);
@@ -100,37 +93,52 @@ extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx
*hctx);
void blk_mq_release(struct request_queue *q);
+/*
+ * If the state of request @rq equals @old_s, update deadline and request state
+ * atomically to @time and @new_s. blk-mq only.
+ */
+static inline bool blk_mq_rq_set_deadline(struct request *rq,
+ unsigned long new_time, enum mq_rq_state old_state,
+ enum mq_rq_state new_state)
+{
+ unsigned long old_val, new_val;
+
+ do {
+ old_val = rq->__deadline;
+ if ((old_val & RQ_STATE_MASK) != old_state)
+ return false;
+ new_val = (new_time & ~RQ_STATE_MASK) |
+ (new_state & RQ_STATE_MASK);
+ } while (cmpxchg(&rq->__deadline, old_val, new_val) != old_val);
+
+ return true;
+}
+
/**
* blk_mq_rq_state() - read the current MQ_RQ_* state of a request
* @rq: target request.
*/
-static inline int blk_mq_rq_state(struct request *rq)
+static inline enum mq_rq_state blk_mq_rq_state(struct request *rq)
{
- return READ_ONCE(rq->gstate) & MQ_RQ_STATE_MASK;
+ return rq->__deadline & RQ_STATE_MASK;
}
/**
- * blk_mq_rq_update_state() - set the current MQ_RQ_* state of a request
- * @rq: target request.
- * @state: new state to set.
+ * blk_mq_change_rq_state - atomically test and set request state
+ * @rq: Request pointer.
+ * @old_state: Old request state.
+ * @new_state: New request state.
*
- * Set @rq's state to @state. The caller is responsible for ensuring that
- * there are no other updaters. A request can transition into IN_FLIGHT
- * only from IDLE and doing so increments the generation number.
+ * Returns %true if and only if the old state was @old and if the state has
+ * been changed into @new.
*/
-static inline void blk_mq_rq_update_state(struct request *rq,
- enum mq_rq_state state)
+static inline bool blk_mq_change_rq_state(struct request *rq,
+ enum mq_rq_state old_state, enum mq_rq_state new_state)
{
- u64 old_val = READ_ONCE(rq->gstate);
- u64 new_val = (old_val & ~MQ_RQ_STATE_MASK) | state;
-
- if (state == MQ_RQ_IN_FLIGHT) {
- WARN_ON_ONCE((old_val & MQ_RQ_STATE_MASK) != MQ_RQ_IDLE);
- new_val += MQ_RQ_GEN_INC;
- }
+ unsigned long old_val = (rq->__deadline & ~RQ_STATE_MASK) | old_state;
+ unsigned long new_val = (rq->__deadline & ~RQ_STATE_MASK) | new_state;
- /* avoid exposing interim values */
- WRITE_ONCE(rq->gstate, new_val);
+ return cmpxchg(&rq->__deadline, old_val, new_val) == old_val;
}
static inline struct blk_mq_ctx *__blk_mq_get_ctx(struct request_queue *q,
diff --git a/block/blk-timeout.c b/block/blk-timeout.c
index 652d4d4d3e97..f666b45415b6 100644
--- a/block/blk-timeout.c
+++ b/block/blk-timeout.c
@@ -162,8 +162,9 @@ void blk_abort_request(struct request *req)
* immediately and that scan sees the new timeout value.
* No need for fancy synchronizations.
*/
- blk_rq_set_deadline(req, jiffies);
- kblockd_schedule_work(&req->q->timeout_work);
+ if (blk_mq_rq_set_deadline(req, jiffies, MQ_RQ_IN_FLIGHT,
+ MQ_RQ_IN_FLIGHT))
+ kblockd_schedule_work(&req->q->timeout_work);
} else {
if (blk_mark_rq_complete(req))
return;
@@ -184,52 +185,17 @@ unsigned long blk_rq_timeout(unsigned long timeout)
return timeout;
}
-/**
- * blk_add_timer - Start timeout timer for a single request
- * @req: request that is about to start running.
- *
- * Notes:
- * Each request has its own timer, and as it is added to the queue, we
- * set up the timer. When the request completes, we cancel the timer.
- */
-void blk_add_timer(struct request *req)
+static void __blk_add_timer(struct request *req)
{
struct request_queue *q = req->q;
unsigned long expiry;
- if (!q->mq_ops)
- lockdep_assert_held(q->queue_lock);
-
- /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
- if (!q->mq_ops && !q->rq_timed_out_fn)
- return;
-
- BUG_ON(!list_empty(&req->timeout_list));
-
- /*
- * Some LLDs, like scsi, peek at the timeout to prevent a
- * command from being retried forever.
- */
- if (!req->timeout)
- req->timeout = q->rq_timeout;
-
- blk_rq_set_deadline(req, jiffies + req->timeout);
- req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
-
- /*
- * Only the non-mq case needs to add the request to a protected list.
- * For the mq case we simply scan the tag map.
- */
- if (!q->mq_ops)
- list_add_tail(&req->timeout_list, &req->q->timeout_list);
-
/*
* If the timer isn't already pending or this timeout is earlier
* than an existing one, modify the timer. Round up to next nearest
* second.
*/
expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));
-
if (!timer_pending(&q->timeout) ||
time_before(expiry, q->timeout.expires)) {
unsigned long diff = q->timeout.expires - expiry;
@@ -244,5 +210,53 @@ void blk_add_timer(struct request *req)
if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
mod_timer(&q->timeout, expiry);
}
+}
+
+/**
+ * blk_add_timer - Start timeout timer for a single request
+ * @req: request that is about to start running.
+ *
+ * Notes:
+ * Each request has its own timer, and as it is added to the queue, we
+ * set up the timer. When the request completes, we cancel the timer.
+ */
+void blk_add_timer(struct request *req)
+{
+ struct request_queue *q = req->q;
+
+ lockdep_assert_held(q->queue_lock);
+
+ if (!q->rq_timed_out_fn)
+ return;
+ if (!req->timeout)
+ req->timeout = q->rq_timeout;
+
+ blk_rq_set_deadline(req, jiffies + req->timeout);
+ list_add_tail(&req->timeout_list, &req->q->timeout_list);
+
+ return __blk_add_timer(req);
+}
+
+/**
+ * blk_mq_add_timer - set the deadline for a single request
+ * @req: request for which to set the deadline.
+ * @old: current request state.
+ * @new: new request state.
+ *
+ * Sets the deadline of a request if and only if it has state @old and
+ * at the same time changes the request state from @old into @new. The caller
+ * must guarantee that the request state won't be modified while this function
+ * is in progress.
+ */
+void blk_mq_add_timer(struct request *req, enum mq_rq_state old,
+ enum mq_rq_state new)
+{
+ struct request_queue *q = req->q;
+
+ if (!req->timeout)
+ req->timeout = q->rq_timeout;
+ if (!blk_mq_rq_set_deadline(req, jiffies + req->timeout, old, new))
+ WARN_ON_ONCE(1);
+ return __blk_add_timer(req);
}
diff --git a/block/blk.h b/block/blk.h
index b034fd2460c4..e0d6e9eb55a3 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -170,6 +170,8 @@ static inline bool bio_integrity_endio(struct bio *bio)
void blk_timeout_work(struct work_struct *work);
unsigned long blk_rq_timeout(unsigned long timeout);
void blk_add_timer(struct request *req);
+void blk_mq_add_timer(struct request *req, enum mq_rq_state old,
+ enum mq_rq_state new);
void blk_delete_timer(struct request *);
@@ -311,15 +313,16 @@ static inline void req_set_nomerge(struct request_queue
*q, struct request *req)
* Steal a bit from this field for legacy IO path atomic IO marking. Note that
* setting the deadline clears the bottom bit, potentially clearing the
* completed bit. The user has to be OK with this (current ones are fine).
+ * Must be called with the request queue lock held.
*/
static inline void blk_rq_set_deadline(struct request *rq, unsigned long time)
{
- rq->__deadline = time & ~0x1UL;
+ rq->__deadline = time & ~RQ_STATE_MASK;
}
static inline unsigned long blk_rq_deadline(struct request *rq)
{
- return rq->__deadline & ~0x1UL;
+ return rq->__deadline & ~RQ_STATE_MASK;
}
/*
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 8efcf49796a3..13ccbb418e89 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -51,7 +51,6 @@ struct blk_mq_hw_ctx {
unsigned int queue_num;
atomic_t nr_active;
- unsigned int nr_expired;
struct hlist_node cpuhp_dead;
struct kobject kobj;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9af3e0f430bc..cde8cf6a359d 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -27,7 +27,6 @@
#include <linux/percpu-refcount.h>
#include <linux/scatterlist.h>
#include <linux/blkzoned.h>
-#include <linux/seqlock.h>
#include <linux/u64_stats_sync.h>
struct module;
@@ -125,10 +124,8 @@ typedef __u32 __bitwise req_flags_t;
#define RQF_SPECIAL_PAYLOAD ((__force req_flags_t)(1 << 18))
/* The per-zone write lock is held for this request */
#define RQF_ZONE_WRITE_LOCKED ((__force req_flags_t)(1 << 19))
-/* timeout is expired */
-#define RQF_MQ_TIMEOUT_EXPIRED ((__force req_flags_t)(1 << 20))
/* already slept for hybrid poll */
-#define RQF_MQ_POLL_SLEPT ((__force req_flags_t)(1 << 21))
+#define RQF_MQ_POLL_SLEPT ((__force req_flags_t)(1 << 20))
/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \
@@ -226,27 +223,10 @@ struct request {
unsigned int extra_len; /* length of alignment and padding */
/*
- * On blk-mq, the lower bits of ->gstate (generation number and
- * state) carry the MQ_RQ_* state value and the upper bits the
- * generation number which is monotonically incremented and used to
- * distinguish the reuse instances.
- *
- * ->gstate_seq allows updates to ->gstate and other fields
- * (currently ->deadline) during request start to be read
- * atomically from the timeout path, so that it can operate on a
- * coherent set of information.
+ * Access through proper helps only as it encodes request state as well:
*/
- seqcount_t gstate_seq;
- u64 gstate;
-
- /*
- * ->aborted_gstate is used by the timeout to claim a specific
- * recycle instance of this request. See blk_mq_timeout_work().
- */
- struct u64_stats_sync aborted_gstate_sync;
- u64 aborted_gstate;
-
- /* access through blk_rq_set_deadline, blk_rq_deadline */
+#define RQ_STATE_BITS 2
+#define RQ_STATE_MASK ((1UL << RQ_STATE_BITS) - 1)
unsigned long __deadline;
struct list_head timeout_list;
