• Kemeng Shi's avatar
    block, bfq: correctly raise inject limit in bfq_choose_bfqq_for_injection · 0c3e09e8
    Kemeng Shi authored
    Function bfq_choose_bfqq_for_injection may temporarily raise inject limit
    to one request if current inject_limit is 0 before search of the source
    queue for injection. However the search below will reset inject limit to
    bfqd->in_service_queue which is zero for raised inject limit. Then the
    temporarily raised inject limit never works as expected.
    Assigment limit to bfqd->in_service_queue in search is needed as limit
    maybe overwriten to min_t(unsigned int, 1, limit) for condition that
    a large in-flight request is on non-rotational devices in found queue.
    So we need to reset limit to bfqd->in_service_queue for normal case.
    
    Actually, we have already make sure bfqd->rq_in_driver is < limit before
    search, then
     -Limit is >= 1 as bfqd->rq_in_driver is >= 0. Then min_t(unsigned int,
    1, limit) is always 1. So we can simply check bfqd->rq_in_driver with
    1 instead of result of min_t(unsigned int, 1, limit) for larget request in
    non-rotational device case to avoid overwritting limit and the bug is gone.
     -For normal case, we have already check bfqd->rq_in_driver is < limit,
    so we can return found bfqq unconditionally to remove unncessary check.
    Signed-off-by: default avatarKemeng Shi <shikemeng@huaweicloud.com>
    Reviewed-by: default avatarJan Kara <jack@suse.cz>
    Link: https://lore.kernel.org/r/20230116095153.3810101-2-shikemeng@huaweicloud.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
    0c3e09e8
bfq-iosched.c 264 KB