Re: [PATCH 7/8] IB/srp: Register the indirect data buffer descriptor

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 8/11/2015 3:09 AM, Bart Van Assche wrote:
> Instead of always using the global rkey for the indirect data
> buffer descriptor, register that descriptor with the HCA if
> the kernel module parameter register_always has been set to Y.
>
> Signed-off-by: Bart Van Assche <bart.vanassche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>
> ---
>   drivers/infiniband/ulp/srp/ib_srp.c | 57 +++++++++++++++++++++++++++++++++++--
>   drivers/infiniband/ulp/srp/ib_srp.h |  4 +++
>   2 files changed, 58 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c
> index 1029fd2..2a16ab4 100644
> --- a/drivers/infiniband/ulp/srp/ib_srp.c
> +++ b/drivers/infiniband/ulp/srp/ib_srp.c
> @@ -1453,18 +1453,58 @@ out:
>   	return ret;
>   }
>
> +/*
> + * Register the indirect data buffer descriptor with the HCA.
> + *
> + * Note: since the indirect data buffer descriptor has been allocated with
> + * kmalloc() it is guaranteed that this buffer is a physically contiguous
> + * memory buffer.
> + */

kdoc style?

> +static int srp_map_idb(struct srp_rdma_ch *ch, struct srp_request *req,
> +		       void **next_mr, void **end_mr, u32 idb_len,
> +		       __be32 *idb_rkey)
> +{
> +	struct srp_target_port *target = ch->target;
> +	struct srp_device *dev = target->srp_host->srp_dev;
> +	struct srp_map_state state;
> +	struct srp_direct_buf idb_desc;
> +	u64 idb_pages[1];
> +	int ret;
> +
> +	memset(&state, 0, sizeof(state));
> +	memset(&idb_desc, 0, sizeof(idb_desc));
> +	state.gen.next = next_mr;
> +	state.gen.end = end_mr;
> +	state.desc = &idb_desc;
> +	state.pages = idb_pages;
> +	state.pages[0] = (req->indirect_dma_addr &
> +			  dev->mr_page_mask);
> +	state.npages = 1;
> +	state.base_dma_addr = req->indirect_dma_addr;
> +	state.dma_len = idb_len;
> +	ret = srp_finish_mapping(&state, ch);
> +	if (ret < 0)
> +		goto out;
> +
> +	*idb_rkey = idb_desc.key;
> +
> +out:
> +	return ret;
> +}
> +
>   static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
>   			struct srp_request *req)
>   {
>   	struct srp_target_port *target = ch->target;
>   	struct scatterlist *scat;
>   	struct srp_cmd *cmd = req->cmd->buf;
> -	int len, nents, count;
> +	int len, nents, count, ret;
>   	struct srp_device *dev;
>   	struct ib_device *ibdev;
>   	struct srp_map_state state;
>   	struct srp_indirect_buf *indirect_hdr;
> -	u32 table_len;
> +	u32 idb_len, table_len;
> +	__be32 idb_rkey;
>   	u8 fmt;
>
>   	if (!scsi_sglist(scmnd) || scmnd->sc_data_direction == DMA_NONE)
> @@ -1546,6 +1586,7 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
>
>   	count = min(state.ndesc, target->cmd_sg_cnt);
>   	table_len = state.ndesc * sizeof (struct srp_direct_buf);
> +	idb_len = sizeof(struct srp_indirect_buf) + table_len;
>
>   	fmt = SRP_DATA_DESC_INDIRECT;
>   	len = sizeof(struct srp_cmd) + sizeof (struct srp_indirect_buf);
> @@ -1554,8 +1595,18 @@ static int srp_map_data(struct scsi_cmnd *scmnd, struct srp_rdma_ch *ch,
>   	memcpy(indirect_hdr->desc_list, req->indirect_desc,
>   	       count * sizeof (struct srp_direct_buf));
>
> +	if (register_always && (dev->use_fast_reg || dev->use_fmr)) {
> +		ret = srp_map_idb(ch, req, state.gen.next, state.gen.end,
> +				  idb_len, &idb_rkey);
> +		if (ret < 0)
> +			return ret;
> +		req->nmdesc++;
> +	} else {
> +		idb_rkey = target->rkey;
> +	}
> +
>   	indirect_hdr->table_desc.va = cpu_to_be64(req->indirect_dma_addr);
> -	indirect_hdr->table_desc.key = cpu_to_be32(target->rkey);
> +	indirect_hdr->table_desc.key = idb_rkey;
>   	indirect_hdr->table_desc.len = cpu_to_be32(table_len);
>   	indirect_hdr->len = cpu_to_be32(state.total_len);
>
> diff --git a/drivers/infiniband/ulp/srp/ib_srp.h b/drivers/infiniband/ulp/srp/ib_srp.h
> index 60a33c1..255b0e5 100644
> --- a/drivers/infiniband/ulp/srp/ib_srp.h
> +++ b/drivers/infiniband/ulp/srp/ib_srp.h
> @@ -288,6 +288,10 @@ struct srp_map_state {
>   			struct srp_fr_desc **next;
>   			struct srp_fr_desc **end;
>   		} fr;
> +		struct {
> +			void		   **next;
> +			void		   **end;
> +		} gen;

What does 'gen' stands for?
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