Thanks for the ping, apologies for the delay.
On Mon, Oct 16, 2017 at 12:14:33PM -0400, Chuck Lever wrote:
> During each NFSv4 callback Call, an RDMA Send completion frees the
> page that contains the RPC Call message. If the upper layer
> determines that a retransmit is necessary, this is too soon.
>
> One possible symptom: after a GARBAGE_ARGS response an NFSv4.1
> callback request, the following BUG fires on the NFS server:
...
> It would be great if this could go into v4.14-rc, but I can live
> with v4.15.
OK, I'll be slightly lazy and queue this up for 4.15....
> Jeff's review suggested adding a comment documenting the requirement
> that rqst->rq_buffer is backed by a single page. However, all of the
> server-side transport mechanics are page-based, so I'm not sure this
> wouldn't be a redundant comment. Suggestions welcome.
If it's always a page then I guess the way to make it ridiculously
obvious would be to keep a pointer to the page instead and use
page_address() as necessary, but.... I'm guessing that's inconvenient
for other users.
So, no suggestions.
--b.
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> index ec37ad8..1854db2 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> @@ -132,6 +132,10 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
> if (ret)
> goto out_err;
>
> + /* Bump page refcnt so Send completion doesn't release
> + * the rq_buffer before all retransmits are complete.
> + */
> + get_page(virt_to_page(rqst->rq_buffer));
> ret = svc_rdma_post_send_wr(rdma, ctxt, 1, 0);
> if (ret)
> goto out_unmap;
> @@ -164,7 +168,6 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
> return -EINVAL;
> }
>
> - /* svc_rdma_sendto releases this page */
> page = alloc_page(RPCRDMA_DEF_GFP);
> if (!page)
> return -ENOMEM;
> @@ -183,6 +186,7 @@ static int svc_rdma_bc_sendto(struct svcxprt_rdma *rdma,
> {
> struct rpc_rqst *rqst = task->tk_rqstp;
>
> + put_page(virt_to_page(rqst->rq_buffer));
> kfree(rqst->rq_rbuffer);
> }
>
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