Hi Jens
On 10/26/18 10:25 PM, Jens Axboe wrote:
> On 10/26/18 3:28 AM, Jianchao Wang wrote:
>> There are two cases when handle DISCARD merge.
>> If max_discard_segments == 1, the bios/requests need to be contiguous
>> to merge. If max_discard_segments > 1, it takes every bio as a range
>> and different range needn't to be contiguous.
>>
>> But now, attempt_merge screws this up. It always consider contiguity
>> for DISCARD for the case max_discard_segments > 1 and cannot merge
>> contiguous DISCARD for the case max_discard_segments == 1, because
>> rq_attempt_discard_merge always returns false in this case.
>> This patch fixes both of the two cases above.
>
> Looks good to me, but:
>
>> diff --git a/block/blk-merge.c b/block/blk-merge.c
>> index 42a4674..cf817c7a 100644
>> --- a/block/blk-merge.c
>> +++ b/block/blk-merge.c
>> @@ -714,6 +714,32 @@ static void blk_account_io_merge(struct request *req)
>> part_stat_unlock();
>> }
>> }
>> +/*
>> + * Two cases of handling DISCARD merge:
>> + * If max_discard_segments > 1, the driver takes every bio
>> + * as a range and send them to controller together. The ranges
>> + * needn't to be contiguous.
>> + * Otherwise, the bios/requests will be handled as same as
>> + * others which should be contiguous.
>> + */
>> +static inline bool blk_discard_mergable(struct request *req)
>> +{
>> + if (req_op(req) == REQ_OP_DISCARD &&
>> + queue_max_discard_segments(req->q) > 1)
>> + return true;
>> + else
>> + return false;
>> +}
>
> Please get rid of the redundant else.
>
OK, I will change it and post next version.
Thanks
Jianchao
