[PATCH] CFQ: request <-> request merging rr_list fixup
In very rare circumstances would we be pruning a merged request and at the same time delete the implicated cfqq from the rr_list, and not readd it when the merged request got added. This could cause io stalls until that process issued io again. Fix it up by putting the rr_list add handling into cfq_add_rq_rb(), identical to how pruning is handled in cfq_del_rq_rb(). This fixes a hang reproducible with fsx-linux. Signed-off-by: Jens Axboe <jens.axboe@oracle.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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@ -456,6 +456,9 @@ static void cfq_add_rq_rb(struct request *rq)
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*/
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while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
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cfq_dispatch_insert(cfqd->queue, __alias);
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if (!cfq_cfqq_on_rr(cfqq))
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cfq_add_cfqq_rr(cfqd, cfqq);
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}
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static inline void
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@ -1652,9 +1655,6 @@ static void cfq_insert_request(request_queue_t *q, struct request *rq)
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cfq_add_rq_rb(rq);
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if (!cfq_cfqq_on_rr(cfqq))
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cfq_add_cfqq_rr(cfqd, cfqq);
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list_add_tail(&rq->queuelist, &cfqq->fifo);
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cfq_rq_enqueued(cfqd, cfqq, rq);
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