On 10/26/18 4:07 PM, Christoph Hellwig wrote: > On Fri, Oct 26, 2018 at 04:05:00PM +0800, jianchao.wang wrote: >> Would anyone please take a look at this ? > > I did take a look and reply to it.. Oh sorry, I missed it in my email client. Got it from the https://lkml.org/lkml/2018/10/24/491 And we could also have a blk_merge_req_ok there. :) Thanks Jianchao > >> >> Thanks in advance. >> Jianchao >> >> On 10/24/18 11:07 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. >>> >>> Signed-off-by: Jianchao Wang <jianchao.w.wang@xxxxxxxxxx> >>> --- >>> >>> V3: >>> - Introduce blk_discard_mergable into attempt_merge and >>> blk_try_merge. >>> - Some comment changes. >>> >>> V2: >>> - Add max_discard_segments > 1 checking in attempt_merge. >>> - Change patch title and comment. >>> - Add more comment in attempt_merge >>> >>> block/blk-merge.c | 34 ++++++++++++++++++++++++---------- >>> 1 file changed, 24 insertions(+), 10 deletions(-) >>> >>> diff --git a/block/blk-merge.c b/block/blk-merge.c >>> index 42a4674..b258de0 100644 >>> --- a/block/blk-merge.c >>> +++ b/block/blk-merge.c >>> @@ -714,6 +714,22 @@ 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; >>> +} >>> >>> /* >>> * For non-mq, this has to be called with the request spinlock acquired. >>> @@ -731,12 +747,6 @@ static struct request *attempt_merge(struct request_queue *q, >>> if (req_op(req) != req_op(next)) >>> return NULL; >>> >>> - /* >>> - * not contiguous >>> - */ >>> - if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)) >>> - return NULL; >>> - >>> if (rq_data_dir(req) != rq_data_dir(next) >>> || req->rq_disk != next->rq_disk >>> || req_no_special_merge(next)) >>> @@ -760,11 +770,16 @@ static struct request *attempt_merge(struct request_queue *q, >>> * counts here. Handle DISCARDs separately, as they >>> * have separate settings. >>> */ >>> - if (req_op(req) == REQ_OP_DISCARD) { >>> + >>> + if (blk_discard_mergable(req)) { >>> if (!req_attempt_discard_merge(q, req, next)) >>> return NULL; >>> - } else if (!ll_merge_requests_fn(q, req, next)) >>> + } else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) { >>> + if (!ll_merge_requests_fn(q, req, next)) >>> + return NULL; >>> + } else { >>> return NULL; >>> + } >>> >>> /* >>> * If failfast settings disagree or any of the two is already >>> @@ -888,8 +903,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio) >>> >>> enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) >>> { >>> - if (req_op(rq) == REQ_OP_DISCARD && >>> - queue_max_discard_segments(rq->q) > 1) >>> + if (blk_discard_mergable(rq)) >>> return ELEVATOR_DISCARD_MERGE; >>> else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) >>> return ELEVATOR_BACK_MERGE; >>> > ---end quoted text--- >
