| Message ID | 1540641134-21485-1-git-send-email-jianchao.w.wang@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V5] block: fix the DISCARD request merge | expand |
On Sat, Oct 27, 2018 at 07:52:14PM +0800, Jianchao Wang wrote: > +enum elv_merge blk_try_req_merge(struct request *req, struct request *next) > +{ > + if (blk_discard_mergable(req)) > + return ELEVATOR_DISCARD_MERGE; > + else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) > + return ELEVATOR_BACK_MERGE; > + > + return ELEVATOR_NO_MERGE; The empty line here look a little odd, but if that is the only thing I can nitpick about it must be great, so: Reviewed-by: Christoph Hellwig <hch@lst.de>
On Sat, Oct 27, 2018 at 7:50 PM Jianchao Wang <jianchao.w.wang@oracle.com> 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@oracle.com> > --- > > V5: > - get rid of the redundant 'else' in blk_discard_mergable > > V4: > - introduce blk_try_req_merge as suggestion of Christoph. > > 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 | 46 ++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 36 insertions(+), 10 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 42a4674..6b5ad27 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -714,6 +714,31 @@ 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; > + return false; > +} > + > +enum elv_merge blk_try_req_merge(struct request *req, struct request *next) > +{ > + if (blk_discard_mergable(req)) > + return ELEVATOR_DISCARD_MERGE; > + else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) > + return ELEVATOR_BACK_MERGE; > + > + return ELEVATOR_NO_MERGE; > +} > > /* > * For non-mq, this has to be called with the request spinlock acquired. > @@ -731,12 +756,6 @@ 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 +779,19 @@ 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) { > + > + switch (blk_try_req_merge(req, next)) { > + case ELEVATOR_DISCARD_MERGE: > if (!req_attempt_discard_merge(q, req, next)) > return NULL; > - } else if (!ll_merge_requests_fn(q, req, next)) > + break; > + case ELEVATOR_BACK_MERGE: > + if (!ll_merge_requests_fn(q, req, next)) > + return NULL; > + break; > + default: > return NULL; > + } > > /* > * If failfast settings disagree or any of the two is already > @@ -888,8 +915,7 @@ 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; > -- > 2.7.4 > Reviewed-by: Ming Lei <ming.lei@redhat.com>
On 10/27/18 5:52 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. Applied, thanks.
diff --git a/block/blk-merge.c b/block/blk-merge.c index 42a4674..6b5ad27 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -714,6 +714,31 @@ 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; + return false; +} + +enum elv_merge blk_try_req_merge(struct request *req, struct request *next) +{ + if (blk_discard_mergable(req)) + return ELEVATOR_DISCARD_MERGE; + else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next)) + return ELEVATOR_BACK_MERGE; + + return ELEVATOR_NO_MERGE; +} /* * For non-mq, this has to be called with the request spinlock acquired. @@ -731,12 +756,6 @@ 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 +779,19 @@ 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) { + + switch (blk_try_req_merge(req, next)) { + case ELEVATOR_DISCARD_MERGE: if (!req_attempt_discard_merge(q, req, next)) return NULL; - } else if (!ll_merge_requests_fn(q, req, next)) + break; + case ELEVATOR_BACK_MERGE: + if (!ll_merge_requests_fn(q, req, next)) + return NULL; + break; + default: return NULL; + } /* * If failfast settings disagree or any of the two is already @@ -888,8 +915,7 @@ 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;
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@oracle.com> --- V5: - get rid of the redundant 'else' in blk_discard_mergable V4: - introduce blk_try_req_merge as suggestion of Christoph. 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 | 46 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 36 insertions(+), 10 deletions(-)