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SubjectRe: [RFC][PATCH 3/3] Do not use rqhash when merges disabled
Aaron Carroll wrote:
> Hi Alan,
>
> Alan D. Brunelle wrote:
>> --- a/block/elevator.c
>> +++ b/block/elevator.c
>> @@ -313,7 +313,7 @@ static inline void __elv_rqhash_del(struct request
>> *rq)
>>
>> static void elv_rqhash_del(struct request_queue *q, struct request *rq)
>> {
>> - if (ELV_ON_HASH(rq))
>> + if (!blk_queue_nomerges(q) && ELV_ON_HASH(rq))
>> __elv_rqhash_del(rq);
>> }
>
> If you switch the nomerges tunable while requests are in flight, it is
> possible that
> a request is put into the rqhash table but not removed here, leading to
> the BUG_ON
> in elv_dequeue_request() triggering. ELV_ON_HASH needs to be checked
> regardless of
> the nomerges state.
>
>
> -- Aaron
>
>

Hi Aaron -

Good catch - that was a last minute addition, the ELV_ON_HASH should be
sufficient without the check for blk_queue_nomerges, right?

Alan


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