maillist inclusion category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IAMMUG CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/commit...
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Consider the following merge chain:
Process 1 Process 2 Process 3 Process 4 (BIC1) (BIC2) (BIC3) (BIC4) Λ | | | --------------\ -------------\ -------------| V V V bfqq1--------->bfqq2---------->bfqq3----------->bfqq4
IO from Process 1 will get bfqf2 from BIC1 first, then bfq_setup_cooperator() will found bfqq2 already merged to bfqq3 and then handle this IO from bfqq3. However, the merge chain can be much deeper and bfqq3 can be merged to other bfqq as well.
Fix this problem by iterating to the last bfqq in bfq_setup_cooperator().
Fixes: 36eca8948323 ("block, bfq: add Early Queue Merge (EQM)") Signed-off-by: Yu Kuai yukuai3@huawei.com Link: https://lore.kernel.org/r/20240902130329.3787024-3-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk --- block/bfq-iosched.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 7d13420a16d6..bdb7ceb68089 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2911,8 +2911,12 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq, struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[a_idx];
/* if a merge has already been setup, then proceed with that first */ - if (bfqq->new_bfqq) - return bfqq->new_bfqq; + new_bfqq = bfqq->new_bfqq; + if (new_bfqq) { + while (new_bfqq->new_bfqq) + new_bfqq = new_bfqq->new_bfqq; + return new_bfqq; + }
/* * Check delayed stable merge for rotational or non-queueing