Re: [PATCH] block: streamline merge possibility checks

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On 12/19/19 3:41 AM, Dmitry Fomichev wrote:
> Checks for data direction in attempt_merge() and blk_rq_merge_ok()

Speak about these two functions, do you think attempt_merge() can be built on blk_rq_merge_ok()?
Things like..
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 48e6725..2a00c4c 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -724,28 +724,7 @@ static enum elv_merge blk_try_req_merge(struct request *req,
 static struct request *attempt_merge(struct request_queue *q,
                                     struct request *req, struct request *next)
 {
-       if (!rq_mergeable(req) || !rq_mergeable(next))
-               return NULL;
-
-       if (req_op(req) != req_op(next))
-               return NULL;
-
-       if (rq_data_dir(req) != rq_data_dir(next)
-           || req->rq_disk != next->rq_disk)
-               return NULL;
-
-       if (req_op(req) == REQ_OP_WRITE_SAME &&
-           !blk_write_same_mergeable(req->bio, next->bio))
-               return NULL;
-
-       /*
-        * Don't allow merge of different write hints, or for a hint with
-        * non-hint IO.
-        */
-       if (req->write_hint != next->write_hint)
-               return NULL;
-
-       if (req->ioprio != next->ioprio)
+       if (!blk_rq_merge_ok(req, next->bio))
                return NULL;


> are redundant and will always succeed when the both I/O request
> operations are equal. Therefore, remove them.
> 
> Signed-off-by: Dmitry Fomichev <dmitry.fomichev@xxxxxxx>
> ---
>  block/blk-merge.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index d783bdc4559b..796451aed7d6 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -745,8 +745,7 @@ static struct request *attempt_merge(struct request_queue *q,
>  	if (req_op(req) != req_op(next))
>  		return NULL;
>  
> -	if (rq_data_dir(req) != rq_data_dir(next)
> -	    || req->rq_disk != next->rq_disk)
> +	if (req->rq_disk != next->rq_disk)
>  		return NULL;
>  
>  	if (req_op(req) == REQ_OP_WRITE_SAME &&
> @@ -868,10 +867,6 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
>  	if (req_op(rq) != bio_op(bio))
>  		return false;
>  
> -	/* different data direction or already started, don't merge */
> -	if (bio_data_dir(bio) != rq_data_dir(rq))
> -		return false;
> -
>  	/* must be same device */
>  	if (rq->rq_disk != bio->bi_disk)
>  		return false;
> 




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