| Message ID | 20210113100937.8278-1-jack@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/3] bfq: Avoid false bfq queue merging | expand |
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 9e4eb0fc1c16..dc5f12d0d482 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2937,6 +2937,7 @@ static void __bfq_set_in_service_queue(struct bfq_data *bfqd, } bfqd->in_service_queue = bfqq; + bfqd->in_serv_last_pos = -1; } /*
bfq_setup_cooperator() uses bfqd->in_serv_last_pos so detect whether it makes sense to merge current bfq queue with the in-service queue. However if the in-service queue is freshly scheduled and didn't dispatch any requests yet, bfqd->in_serv_last_pos is stale and contains value from the previously scheduled bfq queue which can thus result in a bogus decision that the two queues should be merged. This bug can be observed for example with the following fio jobfile: [global] direct=0 ioengine=sync invalidate=1 size=1g rw=read [reader] numjobs=4 directory=/mnt where the 4 processes will end up in the one shared bfq queue although they do IO to physically very distant files (for some reason I was able to observe this only with slice_idle=1ms setting). Fix the problem by invalidating bfqd->in_serv_last_pos when switching in-service queue. Fixes: 058fdecc6de7 ("block, bfq: fix in-service-queue check for queue merging") CC: stable@vger.kernel.org Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> --- block/bfq-iosched.c | 1 + 1 file changed, 1 insertion(+)