Revert "Revert "block, bfq: honor already-setup queue merges""

[ Upstream commit 15729ff814 ]

A crash [1] happened to be triggered in conjunction with commit
2d52c58b9c ("block, bfq: honor already-setup queue merges"). The
latter was then reverted by commit ebc69e897e ("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 d29bd41428
("block, bfq: reset last_bfqq_created on group change").

So, there is no point in keeping commit 2d52c58b9c ("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>
This commit is contained in:
Paolo Valente 2021-11-25 19:15:10 +01:00 коммит произвёл Greg Kroah-Hartman
Родитель 5b8d69c8c1
Коммит 65d8a73745
1 изменённых файлов: 13 добавлений и 3 удалений

Просмотреть файл

@ -2662,6 +2662,15 @@ bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
* are likely to increase the throughput.
*/
bfqq->new_bfqq = new_bfqq;
/*
* The above assignment schedules the following redirections:
* each time some I/O for bfqq arrives, the process that
* generated that I/O is disassociated from bfqq and
* associated with new_bfqq. Here we increases new_bfqq->ref
* in advance, adding the number of processes that are
* expected to be associated with new_bfqq as they happen to
* issue I/O.
*/
new_bfqq->ref += process_refs;
return new_bfqq;
}
@ -2724,6 +2733,10 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
{
struct bfq_queue *in_service_bfqq, *new_bfqq;
/* if a merge has already been setup, then proceed with that first */
if (bfqq->new_bfqq)
return bfqq->new_bfqq;
/*
* Check delayed stable merge for rotational or non-queueing
* devs. For this branch to be executed, bfqq must not be
@ -2825,9 +2838,6 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
if (bfq_too_late_for_merging(bfqq))
return NULL;
if (bfqq->new_bfqq)
return bfqq->new_bfqq;
if (!io_struct || unlikely(bfqq == &bfqd->oom_bfqq))
return NULL;