Hi Jens
On 11/13/18 11:22 AM, Jens Axboe wrote:
> On 11/12/18 2:23 AM, Jianchao Wang wrote:
>> Merge blk_mq_try_issue_directly and __blk_mq_try_issue_directly
>> into one interface to unify the interfaces to issue requests
>> directly. The merged interface takes over the requests totally,
>> it could insert, end or do nothing based on the return value of
>> .queue_rq and 'bypass' parameter. Then caller needn't any other
>> handling any more.
>>
>> To make code clearer, introduce new helpers enum mq_issue_decision
>> and blk_mq_make_decision to decide how to handle the non-issued
>> requests.
>>
>> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx>
>> ---
>> block/blk-mq.c | 108 +++++++++++++++++++++++++++++++++------------------------
>> 1 file changed, 63 insertions(+), 45 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 364a53f..48b7a7c 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -1766,77 +1766,95 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
>> return ret;
>> }
>>
>> -static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
>> +enum mq_issue_decision {
>> + MQ_ISSUE_INSERT_QUEUE,
>> + MQ_ISSUE_END_REQUEST,
>> + MQ_ISSUE_DO_NOTHING,
>> +};
>> +
>> +static inline enum mq_issue_decision
>> + blk_mq_make_dicision(blk_status_t ret, bool bypass)
>> +{
>> + enum mq_issue_decision dec;
>> +
>> + switch(ret) {
>> + case BLK_STS_OK:
>> + dec = MQ_ISSUE_DO_NOTHING;
>> + break;
>> + case BLK_STS_DEV_RESOURCE:
>> + case BLK_STS_RESOURCE:
>> + dec = bypass ? MQ_ISSUE_DO_NOTHING : MQ_ISSUE_INSERT_QUEUE;
>> + break;
>> + default:
>> + dec = bypass ? MQ_ISSUE_DO_NOTHING : MQ_ISSUE_END_REQUEST;
>> + break;
>> + }
>> +
>> + return dec;
>> +}
>
> You seem to mix and match decision and dicision, the former is the
> right spelling.
>
Oops, it's my bad that not find this even in V5 respin.
> But more importantly, not sure I like where this is going, wrapping
> the return value in some other status code. That also makes it a bit
> fragile in terms of adding other status codes, another spot to update.
> Like the decent distinction between RESOURCE and DEV_RESOURCE.
>
> Maybe it is cleaner to just handle this in the caller still?
>
Actually enum mq_issue_decision is introduced to reduce the depth of
'if' branch. And it is indeed not good to introduce another status value.
I will discard enum mq_issue_decision and blk_mq_make_decision in next version.
Thanks
Jianchao
