Re: [PATCH RFC] svcrdma: Fix possible over population fast_reg_page_list

[Sagi Grimberg <sagig@dev.mellanox.co.il>]

On 7/20/2015 8:13 PM, Chuck Lever wrote:
>
> On Jul 20, 2015, at 1:00 PM, Sagi Grimberg <sagig@mellanox.com> wrote:
>
>> When accounting the needed_pages, we need to look into
>> the page_list->max_page_list_len and not the global
>> context xprt->sc_frmr_pg_list_len.
>>
>> Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
>> ---
>> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |    3 ++-
>> 1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> index 2e1348b..b19ffd3 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> @@ -244,7 +244,8 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
>>
>> 	ctxt->direction = DMA_FROM_DEVICE;
>> 	ctxt->frmr = frmr;
>> -	pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len);
>> +	pages_needed = min_t(int, pages_needed,
>> +			     frmr->page_list->max_page_list_len);
>
> This is the last user of sc_frmr_pg_list_len. If Steve thinks this is
> a good change, then why not remove it.
>
> The client uses ib_device_attr::max_fast_reg_page_list_len too.
> Should it be fixed?

I've actually been playing around with this as part of the porting
to the new fast registration API which makes fast_reg_page_list go away.
xprtrdma and svcrdma are switched to use scatterlists instead and
the drivers handle the page lists internally.

So we can remove it, but I think this whole section will go away
eventually.