| Message ID | 20221222191641.1643117-2-shikemeng@huaweicloud.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | A few bugfix and cleancode patch for bfq | expand |
On Fri 23-12-22 03:16:32, Kemeng Shi wrote: > 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: Kemeng Shi <shikemeng@huaweicloud.com> The fix looks good to me. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > block/bfq-iosched.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index a72304c728fc..1220c41fc767 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -4641,12 +4641,10 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) > */ > if (blk_queue_nonrot(bfqd->queue) && > blk_rq_sectors(bfqq->next_rq) >= > - BFQQ_SECT_THR_NONROT) > - limit = min_t(unsigned int, 1, limit); > - else > - limit = in_serv_bfqq->inject_limit; > - > - if (bfqd->rq_in_driver < limit) { > + BFQQ_SECT_THR_NONROT && > + bfqd->rq_in_driver >= 1) > + continue; > + else { > bfqd->rqs_injected = true; > return bfqq; > } > -- > 2.30.0 >
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index a72304c728fc..1220c41fc767 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -4641,12 +4641,10 @@ bfq_choose_bfqq_for_injection(struct bfq_data *bfqd) */ if (blk_queue_nonrot(bfqd->queue) && blk_rq_sectors(bfqq->next_rq) >= - BFQQ_SECT_THR_NONROT) - limit = min_t(unsigned int, 1, limit); - else - limit = in_serv_bfqq->inject_limit; - - if (bfqd->rq_in_driver < limit) { + BFQQ_SECT_THR_NONROT && + bfqd->rq_in_driver >= 1) + continue; + else { bfqd->rqs_injected = true; return bfqq; }
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: Kemeng Shi <shikemeng@huaweicloud.com> --- block/bfq-iosched.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)