[PATCH] Keep track of which page is the 'tail' of an NFSd reply

NFS replies can have a 'tail' after a 'data' component
(for read, readlink, readdir).

For nfsv2 and v3 this tail is in the same page as the head.
For nfsv4, this tail is in a separate page.

We need to keep track of which page so that it right one
gets sent.  This patch does that.

fs/nfsd/nfs3xdr.c

@@ -667,6 +667,7 @@ nfs3svc_encode_readlinkres(struct svc_rqst *rqstp, u32 *p,
 		rqstp->rq_res.page_len = resp->len;
 		if (resp->len & 3) {
 			/* need to pad the tail */
+			rqstp->rq_restailpage = 0;
 			rqstp->rq_res.tail[0].iov_base = p;
 			*p = 0;
 			rqstp->rq_res.tail[0].iov_len = 4 - (resp->len&3);
@@ -691,6 +692,7 @@ nfs3svc_encode_readres(struct svc_rqst *rqstp, u32 *p,
 		rqstp->rq_res.page_len = resp->count;
 		if (resp->count & 3) {
 			/* need to pad the tail */
+			rqstp->rq_restailpage = 0;
 			rqstp->rq_res.tail[0].iov_base = p;
 			*p = 0;
 			rqstp->rq_res.tail[0].iov_len = 4 - (resp->count & 3);

fs/nfsd/nfs4xdr.c

@@ -1735,6 +1735,7 @@ nfsd4_encode_read(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_read
 	svc_take_page(resp->rqstp);
 	resp->xbuf->tail[0].iov_base = 
 		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
+	resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;
 	resp->xbuf->tail[0].iov_len = 0;
 	resp->p = resp->xbuf->tail[0].iov_base;
 	resp->end = resp->p + PAGE_SIZE/4;
@@ -1782,6 +1783,7 @@ nfsd4_encode_readlink(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_r
 	svc_take_page(resp->rqstp);
 	resp->xbuf->tail[0].iov_base = 
 		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
+	resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;
 	resp->xbuf->tail[0].iov_len = 0;
 	resp->p = resp->xbuf->tail[0].iov_base;
 	resp->end = resp->p + PAGE_SIZE/4;
@@ -1859,6 +1861,7 @@ nfsd4_encode_readdir(struct nfsd4_compoundres *resp, int nfserr, struct nfsd4_re
 	svc_take_page(resp->rqstp);
 	resp->xbuf->tail[0].iov_base = 
 		page_address(resp->rqstp->rq_respages[resp->rqstp->rq_resused-1]);
+	resp->rqstp->rq_restailpage = resp->rqstp->rq_resused-1;
 	resp->xbuf->tail[0].iov_len = 0;
 	resp->p = resp->xbuf->tail[0].iov_base;
 	resp->end = resp->p + PAGE_SIZE/4;

fs/nfsd/nfsxdr.c

@@ -396,6 +396,7 @@ nfssvc_encode_readlinkres(struct svc_rqst *rqstp, u32 *p,
 	rqstp->rq_res.page_len = resp->len;
 	if (resp->len & 3) {
 		/* need to pad the tail */
+		rqstp->rq_restailpage = 0;
 		rqstp->rq_res.tail[0].iov_base = p;
 		*p = 0;
 		rqstp->rq_res.tail[0].iov_len = 4 - (resp->len&3);
@@ -415,6 +416,7 @@ nfssvc_encode_readres(struct svc_rqst *rqstp, u32 *p,
 	rqstp->rq_res.page_len = resp->count;
 	if (resp->count & 3) {
 		/* need to pad the tail */
+		rqstp->rq_restailpage = 0;
 		rqstp->rq_res.tail[0].iov_base = p;
 		*p = 0;
 		rqstp->rq_res.tail[0].iov_len = 4 - (resp->count&3);

include/linux/sunrpc/svc.h

@@ -114,6 +114,7 @@ struct svc_rqst {
 	struct xdr_buf		rq_res;
 	struct page *		rq_argpages[RPCSVC_MAXPAGES];
 	struct page *		rq_respages[RPCSVC_MAXPAGES];
+	int			rq_restailpage;
 	short			rq_argused;	/* pages used for argument */
 	short			rq_arghi;	/* pages available in argument page list */
 	short			rq_resused;	/* pages used for result */

net/sunrpc/svcsock.c

@@ -388,7 +388,7 @@ svc_sendto(struct svc_rqst *rqstp, struct xdr_buf *xdr)
 	/* send tail */
 	if (xdr->tail[0].iov_len) {
 		/* The tail *will* be in respages[0]; */
-		result = sock->ops->sendpage(sock, rqstp->rq_respages[0], 
+		result = sock->ops->sendpage(sock, rqstp->rq_respages[rqstp->rq_restailpage], 
 					     ((unsigned long)xdr->tail[0].iov_base)& (PAGE_SIZE-1),
 					     xdr->tail[0].iov_len, 0);