Revert "Revert "block, bfq: honor already-setup queue merges""
[ Upstream commit 15729ff8143f8135b03988a100a19e66d7cb7ecd ] A crash [1] happened to be triggered in conjunction with commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges"). The latter was then reverted by commit ebc69e897e17 ("Revert "block, bfq: honor already-setup queue merges""). Yet, the reverted commit was not the one introducing the bug. In fact, it actually triggered a UAF introduced by a different commit, and now fixed by commit d29bd41428cf ("block, bfq: reset last_bfqq_created on group change"). So, there is no point in keeping commit 2d52c58b9c9b ("block, bfq: honor already-setup queue merges") out. This commit restores it. [1] https://bugzilla.kernel.org/show_bug.cgi?id=214503 Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20211125181510.15004-1-paolo.valente@linaro.org Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -2155,6 +2155,15 @@ bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
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* are likely to increase the throughput.
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* are likely to increase the throughput.
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*/
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*/
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bfqq->new_bfqq = new_bfqq;
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bfqq->new_bfqq = new_bfqq;
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/*
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* The above assignment schedules the following redirections:
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* each time some I/O for bfqq arrives, the process that
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* generated that I/O is disassociated from bfqq and
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* associated with new_bfqq. Here we increases new_bfqq->ref
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* in advance, adding the number of processes that are
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* expected to be associated with new_bfqq as they happen to
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* issue I/O.
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*/
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new_bfqq->ref += process_refs;
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new_bfqq->ref += process_refs;
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return new_bfqq;
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return new_bfqq;
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}
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}
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@ -2214,6 +2223,10 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
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{
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{
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struct bfq_queue *in_service_bfqq, *new_bfqq;
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struct bfq_queue *in_service_bfqq, *new_bfqq;
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/* if a merge has already been setup, then proceed with that first */
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if (bfqq->new_bfqq)
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return bfqq->new_bfqq;
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/*
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/*
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* Prevent bfqq from being merged if it has been created too
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* Prevent bfqq from being merged if it has been created too
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* long ago. The idea is that true cooperating processes, and
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* long ago. The idea is that true cooperating processes, and
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@ -2228,9 +2241,6 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
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if (bfq_too_late_for_merging(bfqq))
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if (bfq_too_late_for_merging(bfqq))
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return NULL;
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return NULL;
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if (bfqq->new_bfqq)
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return bfqq->new_bfqq;
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if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq))
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if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq))
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return NULL;
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return NULL;
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