Re: [PATCH v4 2/5] IB/core, RDMA RW API: Do not exceed QP SGE send limit

[Leon Romanovsky <leon-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

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On Thu, Jul 21, 2016 at 01:03:30PM -0700, Bart Van Assche wrote:
> Compute the SGE limit for RDMA READ and WRITE requests in
> ib_create_qp(). Use that limit in the RDMA RW API implementation.
> 
> Signed-off-by: Bart Van Assche <bart.vanassche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
> Cc: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> Cc: Sagi Grimberg <sagi-NQWnxTmZq1alnMjI0IkVqw@public.gmane.org>
> Cc: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>
> Cc: Parav Pandit <pandit.parav-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Nicholas Bellinger <nab-IzHhD5pYlfBP7FQvKIMDCQ@public.gmane.org>
> Cc: Laurence Oberman <loberman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> #v4.7+
> ---
>  drivers/infiniband/core/rw.c    | 10 ++--------
>  drivers/infiniband/core/verbs.c |  9 +++++++++
>  include/rdma/ib_verbs.h         |  6 ++++++
>  3 files changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/infiniband/core/rw.c b/drivers/infiniband/core/rw.c
> index 1ad2baa..dbfd854 100644
> --- a/drivers/infiniband/core/rw.c
> +++ b/drivers/infiniband/core/rw.c
> @@ -58,13 +58,6 @@ static inline bool rdma_rw_io_needs_mr(struct ib_device *dev, u8 port_num,
>  	return false;
>  }
>  
> -static inline u32 rdma_rw_max_sge(struct ib_device *dev,
> -		enum dma_data_direction dir)
> -{
> -	return dir == DMA_TO_DEVICE ?
> -		dev->attrs.max_sge : dev->attrs.max_sge_rd;
> -}
> -
>  static inline u32 rdma_rw_fr_page_list_len(struct ib_device *dev)
>  {
>  	/* arbitrary limit to avoid allocating gigantic resources */
> @@ -186,7 +179,8 @@ static int rdma_rw_init_map_wrs(struct rdma_rw_ctx *ctx, struct ib_qp *qp,
>  		u64 remote_addr, u32 rkey, enum dma_data_direction dir)
>  {
>  	struct ib_device *dev = qp->pd->device;
> -	u32 max_sge = rdma_rw_max_sge(dev, dir);
> +	u32 max_sge = dir == DMA_TO_DEVICE ? qp->max_write_sge :
> +		      qp->max_read_sge;

Bart,
I'm sure that I missed something.

Can "dir" be DMA_BIDIRECTIONAL?
If yes, mxa_sge will be min(max_write_sge, max_read_sge).

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