svc: Add transport hdr size for defer/revisit

Some transports have a header in front of the RPC header. The current
defer/revisit processing considers only the iov_len and arg_len to
determine how much to back up when saving the original request
to revisit. Add a field to the rqstp structure to save the size
of the transport header so svc_defer can correctly compute
the start of a request.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 29 insertions, 9 deletions

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 23165aef59d9..000c7dc3b82c 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -29,7 +29,6 @@
 #include <linux/sunrpc/types.h>
 #include <linux/sunrpc/clnt.h>
 #include <linux/sunrpc/xdr.h>
-#include <linux/sunrpc/svcsock.h>
 #include <linux/sunrpc/stats.h>
 #include <linux/sunrpc/svc_xprt.h>
 
@@ -859,10 +858,18 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
         svc_xprt_put(xprt);
 }
 
+/*
+ * Save the request off for later processing. The request buffer looks
+ * like this:
+ *
+ * <xprt-header><rpc-header><rpc-pagelist><rpc-tail>
+ *
+ * This code can only handle requests that consist of an xprt-header
+ * and rpc-header.
+ */
 static struct cache_deferred_req *svc_defer(struct cache_req *req)
 {
         struct svc_rqst *rqstp = container_of(req, struct svc_rqst, rq_chandle);
-        int size = sizeof(struct svc_deferred_req) + (rqstp->rq_arg.len);
         struct svc_deferred_req *dr;
 
         if (rqstp->rq_arg.page_len)
@@ -871,8 +878,10 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
                 dr = rqstp->rq_deferred;
                 rqstp->rq_deferred = NULL;
         } else {
-                int skip  = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;
+                size_t skip;
+                size_t size;
                 /* FIXME maybe discard if size too large */
+                size = sizeof(struct svc_deferred_req) + rqstp->rq_arg.len;
                 dr = kmalloc(size, GFP_KERNEL);
                 if (dr == NULL)
                         return NULL;
@@ -883,8 +892,12 @@ static struct cache_deferred_req *svc_defer(struct cache_req *req)
                 dr->addrlen = rqstp->rq_addrlen;
                 dr->daddr = rqstp->rq_daddr;
                 dr->argslen = rqstp->rq_arg.len >> 2;
-                memcpy(dr->args, rqstp->rq_arg.head[0].iov_base-skip,
-                       dr->argslen<<2);
+                dr->xprt_hlen = rqstp->rq_xprt_hlen;
+
+                /* back up head to the start of the buffer and copy */
+                skip = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;
+                memcpy(dr->args, rqstp->rq_arg.head[0].iov_base - skip,
+                       dr->argslen << 2);
         }
         svc_xprt_get(rqstp->rq_xprt);
         dr->xprt = rqstp->rq_xprt;
@@ -900,16 +913,21 @@ static int svc_deferred_recv(struct svc_rqst *rqstp)
 {
         struct svc_deferred_req *dr = rqstp->rq_deferred;
 
-        rqstp->rq_arg.head[0].iov_base = dr->args;
-        rqstp->rq_arg.head[0].iov_len = dr->argslen<<2;
+        /* setup iov_base past transport header */
+        rqstp->rq_arg.head[0].iov_base = dr->args + (dr->xprt_hlen>>2);
+        /* The iov_len does not include the transport header bytes */
+        rqstp->rq_arg.head[0].iov_len = (dr->argslen<<2) - dr->xprt_hlen;
         rqstp->rq_arg.page_len = 0;
-        rqstp->rq_arg.len = dr->argslen<<2;
+        /* The rq_arg.len includes the transport header bytes */
+        rqstp->rq_arg.len     = dr->argslen<<2;
         rqstp->rq_prot        = dr->prot;
         memcpy(&rqstp->rq_addr, &dr->addr, dr->addrlen);
         rqstp->rq_addrlen     = dr->addrlen;
+        /* Save off transport header len in case we get deferred again */
+        rqstp->rq_xprt_hlen   = dr->xprt_hlen;
         rqstp->rq_daddr       = dr->daddr;
         rqstp->rq_respages    = rqstp->rq_pages;
-        return dr->argslen<<2;
+        return (dr->argslen<<2) - dr->xprt_hlen;
 }
 
 
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 343a85b700f0..1d3e5fcc2cc4 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -315,6 +315,8 @@ static int svc_recvfrom(struct svc_rqst *rqstp, struct kvec *iov, int nr,
         };
         int len;
 
+        rqstp->rq_xprt_hlen = 0;
+
         len = kernel_recvmsg(svsk->sk_sock, &msg, iov, nr, buflen,
                                 msg.msg_flags);