RE: [PATCH V6 1/9] RDMA/iser: Limit sg tablesize and max_sectors to device fastreg max depth

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> -----Original Message-----
> From: Jason Gunthorpe [mailto:jgunthorpe@xxxxxxxxxxxxxxxxxxxx]
> Sent: Friday, July 24, 2015 11:41 AM
> To: Steve Wise
> Cc: dledford@xxxxxxxxxx; infinipath@xxxxxxxxx; sagig@xxxxxxxxxxxx; ogerlitz@xxxxxxxxxxxx; roid@xxxxxxxxxxxx; linux-
> rdma@xxxxxxxxxxxxxxx; eli@xxxxxxxxxxxx; target-devel@xxxxxxxxxxxxxxx; linux-nfs@xxxxxxxxxxxxxxx; bfields@xxxxxxxxxxxx
> Subject: Re: [PATCH V6 1/9] RDMA/iser: Limit sg tablesize and max_sectors to device fastreg max depth
> 
> On Fri, Jul 24, 2015 at 11:18:21AM -0500, Steve Wise wrote:
> > Currently the sg tablesize, which dictates fast register page list
> > depth to use, does not take into account the limits of the rdma device.
> > So adjust it once we discover the device fastreg max depth limit.  Also
> > adjust the max_sectors based on the resulting sg tablesize.
> 
> Huh. How does this relate to the max_page_list_len argument:
> 
>  struct ib_mr *ib_alloc_fast_reg_mr(struct ib_pd *pd, int max_page_list_len)
> 
> Shouldn't max_fast_reg_page_list_len be checked during the above?
> 
> Ie does this still make sense:
> 
> drivers/infiniband/ulp/iser/iser_verbs.c:       desc->data_mr = ib_alloc_fast_reg_mr(pd, ISCSI_ISER_SG_TABLESIZE + 1);
> 
> ?
> 
> The only ULP that checks this is SRP, so basically, all our ULPs are
> probably quietly broken? cxgb3 has a limit of 10 (!?!?!!)
> 

Yea seems like some drivers need to enforce this in ib_alloc_fast_reg_mr() as well as ib_alloc_fast_reg_page_list(), and ULPs need
to not exceed the device max.

I will fix iser to limit the mr and page_list allocation based on the device max.

Steve.

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