linux-kernel - Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE

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Date:   Sun, 29 Oct 2023 11:22:53 +0800
From:   Zhu Yanjun <yanjun.zhu@...ux.dev>
To:     Bart Van Assche <bvanassche@....org>,
        Li Zhijian <lizhijian@...itsu.com>, zyjzyj2000@...il.com,
        jgg@...pe.ca, leon@...nel.org, linux-rdma@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, rpearsonhpe@...il.com,
        matsuda-daisuke@...itsu.com
Subject: Re: [PATCH RFC 1/2] RDMA/rxe: don't allow registering !PAGE_SIZE mr

在 2023/10/29 7:07, Bart Van Assche 写道:
> On 10/27/23 19:48, Zhu Yanjun wrote:
>> In this case, ULP with folio will not work well with current RXE after 
>> this commit is applied.
> 
> Why not? RDMA ULPs like the SRP initiator driver use ib_map_mr_sg(). The
> latter function calls rxe_map_mr_sg() if the RXE driver is used. 
> rxe_map_mr_sg() calls ib_sg_to_pages(). ib_sg_to_pages() translates
> SG-entries that are larger than a virtual memory page into multiple
> entries with size mr->page_size.

It seems that we are not on the same page. I am thinking that this fix 
should also work for the future folio. And your idea is based on the 
current implementation.

Perhaps it is not a good time to discuss folio currently. Let me focus 
on the current implementation.

In this commit, if the page size is not equal to PAGE_SIZE, it will pop 
out warning then exit. So "rxe_info_mr" should be changed to rxe_warning_mr?

In fact, I like to remove the page size assignment in rxe, that is, 
partly reverting the commit 325a7eb85199 ("RDMA/rxe: Cleanup page 
variables in rxe_mr.c"). But it seems that Jason did not like this.
I no longer insist on this.

I am not sure whether Jason, Leon, Bob and you have better solution to 
this problem or not.

If not, this commit can fix this problem if no better solution.

Reviewed-by: Zhu Yanjun <yanjun.zhu@...ux.dev>

Thanks,
Zhu Yanjun

> 
> Thanks,
> 
> Bart.
>