From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sagi Grimberg <sagig@dev.mellanox.co.il>
Subject: Re: [PATCH 7/9] IB/core: generic RDMA READ/WRITE API
Date: Thu, 3 Mar 2016 12:53:04 +0200
Message-ID: <56D81790.8090305@dev.mellanox.co.il>
References: <1456784410-20166-1-git-send-email-hch@lst.de>
 <1456784410-20166-8-git-send-email-hch@lst.de>
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To: Christoph Hellwig <hch@lst.de>, linux-rdma@vger.kernel.org
Cc: swise@opengridcomputing.com, sagig@mellanox.com, bart.vanassche@sandisk.com, target-devel@vger.kernel.org
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> +int rdma_rw_init_mrs(struct ib_qp *qp, struct ib_qp_init_attr *attr)
> +{
> +	struct ib_device *dev = qp->pd->device;
> +	int ret = 0;
> +
> +	if (rdma_rw_use_mr(dev, attr->port_num)) {
> +		ret = ib_mr_pool_init(qp, &qp->rdma_mrs,
> +				attr->cap.max_rdma_ctxs, IB_MR_TYPE_MEM_REG,
> +				dev->attrs.max_fast_reg_page_list_len);

Christoph,

This is a problem for mlx5 which exposes:

         props->max_fast_reg_page_list_len = (unsigned int)-1;

Which is obviously wrong and needs to be corrected, but this is sort of
an overkill to allocate max supported unconditionally.

How about choosing a sane default of 256/512 pages for now? I don't
think we'll see a lot of larger transfers in iser/nvmf (which actually
need MRs for iWARP).

Alternatively we can allow the caller to limit the MR size?