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svcrdma: Find rmsgp more reliably

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xdr_start() can return the wrong rmsgp address if an assumption
about how the xdr_buf was constructed changes.  When it gets it
wrong, the client receives a reply that has gibberish in the
RPC/RDMA header, preventing it from matching a waiting RPC request.

Instead, make (and document) just one assumption: that the RDMA
header for the client's RPC call is at the start of the first page
in rq_pages.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2015-01-13 11:03:11 -05:00 committed by J. Bruce Fields
parent 3fe04ee9f9
commit e5523bd281
1 changed files with 4 additions and 14 deletions
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18
net/sunrpc/xprtrdma/svc_rdma_sendto.c
View file

@ -483,18 +483,6 @@ void svc_rdma_prep_reply_hdr(struct svc_rqst *rqstp)
{
}
/*
* Return the start of an xdr buffer.
*/
static void *xdr_start(struct xdr_buf *xdr)
{
return xdr->head[0].iov_base -
(xdr->len -
xdr->page_len -
xdr->tail[0].iov_len -
xdr->head[0].iov_len);
}
int svc_rdma_sendto(struct svc_rqst *rqstp)
{
struct svc_xprt *xprt = rqstp->rq_xprt;
@ -512,8 +500,10 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
dprintk("svcrdma: sending response for rqstp=%p\n", rqstp);
/* Get the RDMA request header. */
rdma_argp = xdr_start(&rqstp->rq_arg);
/* Get the RDMA request header. The receive logic always
* places this at the start of page 0.
*/
rdma_argp = page_address(rqstp->rq_pages[0]);
/* Build an req vec for the XDR */
ctxt = svc_rdma_get_context(rdma);