Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-11-22 12:11:40 +00:00
Code Issues Packages Projects Releases Wiki Activity

blk-mq: fix race with timeouts and requeue events

Browse Source 
If a requeue event races with a timeout, we can get into the
situation where we attempt to complete a request from the
timeout handler when it's not start anymore. This causes a crash.
So have the timeout handler check that REQ_ATOM_STARTED is still
set on the request - if not, we ignore the event. If this happens,
the request has now been marked as complete. As a consequence, we
need to ensure to clear REQ_ATOM_COMPLETE in blk_mq_start_request(),
as to maintain proper request state.

Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2014-04-24 08:51:47 -06:00
parent 70ab0b2d51
commit 87ee7b1121
4 changed files with 42 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
block/blk-mq.c
View File

@ -378,7 +378,15 @@ static void blk_mq_start_request(struct request *rq, bool last)
* REQ_ATOMIC_STARTED is seen.
*/
rq->deadline = jiffies + q->rq_timeout;
/*
* 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.
*/
set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
clear_bit(REQ_ATOM_COMPLETE, &rq->atomic_flags);
if (q->dma_drain_size && blk_rq_bytes(rq)) {
/*
@ -485,6 +493,28 @@ static void blk_mq_hw_ctx_check_timeout(struct blk_mq_hw_ctx *hctx,
blk_mq_tag_busy_iter(hctx->tags, blk_mq_timeout_check, &data);
}
static enum blk_eh_timer_return blk_mq_rq_timed_out(struct request *rq)
{
struct request_queue *q = rq->q;
/*
* 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
* we 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, &rq->atomic_flags))
return BLK_EH_NOT_HANDLED;
if (!q->mq_ops->timeout)
return BLK_EH_RESET_TIMER;
return q->mq_ops->timeout(rq);
}
static void blk_mq_rq_timer(unsigned long data)
{
struct request_queue *q = (struct request_queue *) data;
@ -538,11 +568,6 @@ static bool blk_mq_attempt_merge(struct request_queue *q,
return false;
}
void blk_mq_add_timer(struct request *rq)
{
__blk_add_timer(rq, NULL);
}
/*
* Run this hardware queue, pulling any software queues mapped to it in.
* Note that this function currently has various problems around ordering
@ -799,7 +824,7 @@ static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
/*
* We do this early, to ensure we are on the right CPU.
*/
blk_mq_add_timer(rq);
blk_add_timer(rq);
}
void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue,
@ -1400,7 +1425,7 @@ struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
q->sg_reserved_size = INT_MAX;
blk_queue_make_request(q, blk_mq_make_request);
blk_queue_rq_timed_out(q, set->ops->timeout);
blk_queue_rq_timed_out(q, blk_mq_rq_timed_out);
if (set->timeout)
blk_queue_rq_timeout(q, set->timeout);

2
block/blk-mq.h
View File

@ -51,6 +51,4 @@ void blk_mq_disable_hotplug(void);
extern unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set);
extern int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues);
void blk_mq_add_timer(struct request *rq);
#endif

16
block/blk-timeout.c
View File

@ -96,11 +96,7 @@ static void blk_rq_timed_out(struct request *req)
__blk_complete_request(req);
break;
case BLK_EH_RESET_TIMER:
if (q->mq_ops)
blk_mq_add_timer(req);
else
blk_add_timer(req);
blk_add_timer(req);
blk_clear_rq_complete(req);
break;
case BLK_EH_NOT_HANDLED:
@ -170,7 +166,8 @@ void blk_abort_request(struct request *req)
}
EXPORT_SYMBOL_GPL(blk_abort_request);
void __blk_add_timer(struct request *req, struct list_head *timeout_list)
static void __blk_add_timer(struct request *req,
struct list_head *timeout_list)
{
struct request_queue *q = req->q;
unsigned long expiry;
@ -225,6 +222,11 @@ void __blk_add_timer(struct request *req, struct list_head *timeout_list)
*/
void blk_add_timer(struct request *req)
{
__blk_add_timer(req, &req->q->timeout_list);
struct request_queue *q = req->q;
if (q->mq_ops)
__blk_add_timer(req, NULL);
else
__blk_add_timer(req, &req->q->timeout_list);
}

3
block/blk.h
View File

@ -37,9 +37,8 @@ bool __blk_end_bidi_request(struct request *rq, int error,
void blk_rq_timed_out_timer(unsigned long data);
void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
unsigned int *next_set);
void __blk_add_timer(struct request *req, struct list_head *timeout_list);
void blk_add_timer(struct request *req);
void blk_delete_timer(struct request *);
void blk_add_timer(struct request *);
bool bio_attempt_front_merge(struct request_queue *q, struct request *req,