2018-10-19 09:23:56

by jianchao.wang

Subject: [PATCH] block: don't check position contiguity for DISCARD in attempt_merge

Discard command supports multiple ranges of blocks, so needn't
checking position contiguity when merging. Let's do the same thing
in attempt_merge as the blk_try_merge.

Signed-off-by: Jianchao Wang <[email protected]>
---
block/blk-merge.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 42a4674..c94749b 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -732,9 +732,10 @@ static struct request *attempt_merge(struct request_queue *q,
return NULL;

/*
- * not contiguous
+ * not contiguous, except for DISCARD
*/
- if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
+ if ((req_op(req) != REQ_OP_DISCARD) &&
+ (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)))
return NULL;

if (rq_data_dir(req) != rq_data_dir(next)
--
2.7.4

2018-10-19 09:48:50

by Ming Lei

Subject: Re: [PATCH] block: don't check position contiguity for DISCARD in attempt_merge

On Fri, Oct 19, 2018 at 5:23 PM Jianchao Wang
<[email protected]> wrote:
>
> Discard command supports multiple ranges of blocks, so needn't
> checking position contiguity when merging. Let's do the same thing
> in attempt_merge as the blk_try_merge.
>
> Signed-off-by: Jianchao Wang <[email protected]>
> ---
> block/blk-merge.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 42a4674..c94749b 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -732,9 +732,10 @@ static struct request *attempt_merge(struct request_queue *q,
> return NULL;
>
> /*
> - * not contiguous
> + * not contiguous, except for DISCARD
> */
> - if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
> + if ((req_op(req) != REQ_OP_DISCARD) &&
> + (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next)))
> return NULL;
>
> if (rq_data_dir(req) != rq_data_dir(next)
> --
> 2.7.4
>
Reviewed-by: Ming Lei <[email protected]>

Thanks,
Ming Lei

2018-10-19 15:58:30

by Martin K. Petersen

Subject: Re: [PATCH] block: don't check position contiguity for DISCARD in attempt_merge

Jianchao,

> Discard command supports multiple ranges of blocks, so needn't
> checking position contiguity when merging. Let's do the same thing
> in attempt_merge as the blk_try_merge.

Discards need to be contiguous unless queue->limits.max_discard_segments
is bigger than 1. So if you remove this I think you need to add a
contiguity check in req_attempt_discard_merge().

--
Martin K. Petersen Oracle Linux Engineering

2018-10-20 13:58:32

by jianchao.wang

Subject: Re: [PATCH] block: don't check position contiguity for DISCARD in attempt_merge

Hi Martin

On 10/19/18 11:57 PM, Martin K. Petersen wrote:
>
> Jianchao,
>
>> Discard command supports multiple ranges of blocks, so needn't
>> checking position contiguity when merging. Let's do the same thing
>> in attempt_merge as the blk_try_merge.
>
> Discards need to be contiguous unless queue->limits.max_discard_segments
> is bigger than 1. So if you remove this I think you need to add a
> contiguity check in req_attempt_discard_merge().
>
Yes.

I will send the V2 version next.

Thanks
Jianchao