Re: [PATCH V6 6/9] isert: Rename IO functions to more descriptive names

[Steve Wise <swise@opengridcomputing.com>]

On 7/26/2015 6:00 AM, Sagi Grimberg wrote:
> On 7/26/2015 1:43 PM, Christoph Hellwig wrote:
>> On Sun, Jul 26, 2015 at 01:08:16PM +0300, Sagi Grimberg wrote:
>>> I've given this some thought and I think we should avoid splitting
>>> logic from PI and iWARP. The reason (other than code duplication) is
>>> that currently the iser target support only up to 1MB IOs. I have some
>>> code (not done yet) to support larger IOs by using multiple
>>> registrations  per IO (with or without PI).
>>
>> Just curious: How is this going to work with iSER only having a single
>> rkey/offset/len field?
>>
>
> Good question,
>
> On the wire iser sends a single rkey, but the target is allowed to
> transfer the data however it wants to.
>
> Say that the local target HCA supports only 32 pages (128K bytes for 4K
> pages) registration and the initiator sent:
> rkey=0x1234
> address=0xffffaaaa
> length=512K
>
> The target would allocate a 512K buffer and:
> register offset 0-128K to lkey=0x1
> register offset 128K-256K to lkey=0x2
> register offset 256K-384K to lkey=0x3
> register offset 384K-512K to lkey=0x4
>
> then constructs sg_list as:
> sg_list[0] = {addr=buf, length=128K, lkey=0x1}
> sg_list[1] = {addr=buf+128K, length=128K, lkey=0x2}
> sg_list[2] = {addr=buf+256K, length=128K, lkey=0x3}
> sg_list[3] = {addr=buf+384K, length=128K, lkey=0x4}
>
> Then set rdma_read wr with:
> rdma_r_wr.sg_list=&sg_list
> rdma_r_wr.rdma.addr=0xffffaaaa
> rdma_r_wr.rdma.rkey=0x1234
>
> post_send(rdma_r_wr);
>
> Ideally, the post contains a chain of all 4 registrations and the
> rdma_read (and an opportunistic good scsi response).

Just to be clear: This example is for IB only, correct?  IW would 
require rkeys with REMOTE_WRITE and 4 read wrs.  And you're ignoring 
invalidation wrs (or read-with-inv) in the example...