Re: [PATCH] svcrdma: fix bounce buffers for non-zero page offsets

[Dan Aloni <dan@kernelim.com>]

On Fri, Oct 02, 2020 at 10:54:28AM -0400, Chuck Lever wrote:
> Hi Dan-
> 
> > On Oct 2, 2020, at 10:48 AM, Dan Aloni <dan@kernelim.com> wrote:
> > 
> > This was discovered using O_DIRECT and small unaligned file offsets
> > at the client side.
> > 
> > Fixes: e248aa7be86 ("svcrdma: Remove max_sge check at connect time")
> > Signed-off-by: Dan Aloni <dan@kernelim.com>
> > ---
> > net/sunrpc/xprtrdma/svc_rdma_sendto.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> > index 7b94d971feb3..c991eb1fd4e3 100644
> > --- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> > +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> > @@ -638,7 +638,7 @@ static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma,
> > 		while (remaining) {
> > 			len = min_t(u32, PAGE_SIZE - pageoff, remaining);
> > 
> > -			memcpy(dst, page_address(*ppages), len);
> > +			memcpy(dst, page_address(*ppages) + pageoff, len);
> 
> I'm assuming the only relevant place that sets xdr->page_base
> is nfsd_splice_actor() ?

Yes, and traces at the server indeed indicate that splicing happened.
This works for both tmpfs and ext4 as host FSes.

-- 
Dan Aloni