SUNRPC: Add xdr_set_scratch_page() and xdr_reset_scratch_buffer()

Clean up: De-duplicate some frequently-used code.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfs/blocklayout/blocklayout.c

@@ -697,7 +697,7 @@ bl_alloc_lseg(struct pnfs_layout_hdr *lo, struct nfs4_layoutget_res *lgr,
 
 	xdr_init_decode_pages(&xdr, &buf,
 			lgr->layoutp->pages, lgr->layoutp->len);
-	xdr_set_scratch_buffer(&xdr, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&xdr, scratch);
 
 	status = -EIO;
 	p = xdr_inline_decode(&xdr, 4);

fs/nfs/blocklayout/dev.c

@@ -510,7 +510,7 @@ bl_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
 		goto out;
 
 	xdr_init_decode_pages(&xdr, &buf, pdev->pages, pdev->pglen);
-	xdr_set_scratch_buffer(&xdr, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&xdr, scratch);
 
 	p = xdr_inline_decode(&xdr, sizeof(__be32));
 	if (!p)

fs/nfs/dir.c

@@ -576,7 +576,7 @@ int nfs_readdir_page_filler(nfs_readdir_descriptor_t *desc, struct nfs_entry *en
 		goto out_nopages;
 
 	xdr_init_decode_pages(&stream, &buf, xdr_pages, buflen);
-	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&stream, scratch);
 
 	do {
 		if (entry->label)

fs/nfs/filelayout/filelayout.c

@@ -666,7 +666,7 @@ filelayout_decode_layout(struct pnfs_layout_hdr *flo,
 		return -ENOMEM;
 
 	xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages, lgr->layoutp->len);
-	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&stream, scratch);
 
 	/* 20 = ufl_util (4), first_stripe_index (4), pattern_offset (8),
 	 * num_fh (4) */

fs/nfs/filelayout/filelayoutdev.c

@@ -82,7 +82,7 @@ nfs4_fl_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
 		goto out_err;
 
 	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
-	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&stream, scratch);
 
 	/* Get the stripe count (number of stripe index) */
 	p = xdr_inline_decode(&stream, 4);

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -378,7 +378,7 @@ ff_layout_alloc_lseg(struct pnfs_layout_hdr *lh,
 
 	xdr_init_decode_pages(&stream, &buf, lgr->layoutp->pages,
 			      lgr->layoutp->len);
-	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&stream, scratch);
 
 	/* stripe unit and mirror_array_cnt */
 	rc = -EIO;

fs/nfs/flexfilelayout/flexfilelayoutdev.c

@@ -69,7 +69,7 @@ nfs4_ff_alloc_deviceid_node(struct nfs_server *server, struct pnfs_device *pdev,
 	INIT_LIST_HEAD(&dsaddrs);
 
 	xdr_init_decode_pages(&stream, &buf, pdev->pages, pdev->pglen);
-	xdr_set_scratch_buffer(&stream, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(&stream, scratch);
 
 	/* multipath count */
 	p = xdr_inline_decode(&stream, 4);

fs/nfs/nfs42xdr.c

@@ -1540,7 +1540,7 @@ static int nfs4_xdr_dec_listxattrs(struct rpc_rqst *rqstp,
 	struct compound_hdr hdr;
 	int status;
 
-	xdr_set_scratch_buffer(xdr, page_address(res->scratch), PAGE_SIZE);
+	xdr_set_scratch_page(xdr, res->scratch);
 
 	status = decode_compound_hdr(xdr, &hdr);
 	if (status)

fs/nfs/nfs4xdr.c

@@ -6403,10 +6403,8 @@ nfs4_xdr_dec_getacl(struct rpc_rqst *rqstp, struct xdr_stream *xdr,
 	struct compound_hdr hdr;
 	int status;
 
-	if (res->acl_scratch != NULL) {
-		void *p = page_address(res->acl_scratch);
-		xdr_set_scratch_buffer(xdr, p, PAGE_SIZE);
-	}
+	if (res->acl_scratch != NULL)
+		xdr_set_scratch_page(xdr, res->acl_scratch);
 	status = decode_compound_hdr(xdr, &hdr);
 	if (status)
 		goto out;

fs/nfsd/nfs4proc.c

@@ -2276,7 +2276,7 @@ static void svcxdr_init_encode(struct svc_rqst *rqstp,
 	xdr->end = head->iov_base + PAGE_SIZE - rqstp->rq_auth_slack;
 	/* Tail and page_len should be zero at this point: */
 	buf->len = buf->head[0].iov_len;
-	xdr->scratch.iov_len = 0;
+	xdr_reset_scratch_buffer(xdr);
 	xdr->page_ptr = buf->pages - 1;
 	buf->buflen = PAGE_SIZE * (1 + rqstp->rq_page_end - buf->pages)
 		- rqstp->rq_auth_slack;

include/linux/sunrpc/xdr.h

@@ -248,7 +248,6 @@ extern void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf,
 			    __be32 *p, struct rpc_rqst *rqst);
 extern void xdr_init_decode_pages(struct xdr_stream *xdr, struct xdr_buf *buf,
 		struct page **pages, unsigned int len);
-extern void xdr_set_scratch_buffer(struct xdr_stream *xdr, void *buf, size_t buflen);
 extern __be32 *xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes);
 extern unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len);
 extern void xdr_enter_page(struct xdr_stream *xdr, unsigned int len);
@@ -256,6 +255,49 @@ extern int xdr_process_buf(struct xdr_buf *buf, unsigned int offset, unsigned in
 extern uint64_t xdr_align_data(struct xdr_stream *, uint64_t, uint32_t);
 extern uint64_t xdr_expand_hole(struct xdr_stream *, uint64_t, uint64_t);
 
+/**
+ * xdr_set_scratch_buffer - Attach a scratch buffer for decoding data.
+ * @xdr: pointer to xdr_stream struct
+ * @buf: pointer to an empty buffer
+ * @buflen: size of 'buf'
+ *
+ * The scratch buffer is used when decoding from an array of pages.
+ * If an xdr_inline_decode() call spans across page boundaries, then
+ * we copy the data into the scratch buffer in order to allow linear
+ * access.
+ */
+static inline void
+xdr_set_scratch_buffer(struct xdr_stream *xdr, void *buf, size_t buflen)
+{
+	xdr->scratch.iov_base = buf;
+	xdr->scratch.iov_len = buflen;
+}
+
+/**
+ * xdr_set_scratch_page - Attach a scratch buffer for decoding data
+ * @xdr: pointer to xdr_stream struct
+ * @page: an anonymous page
+ *
+ * See xdr_set_scratch_buffer().
+ */
+static inline void
+xdr_set_scratch_page(struct xdr_stream *xdr, struct page *page)
+{
+	xdr_set_scratch_buffer(xdr, page_address(page), PAGE_SIZE);
+}
+
+/**
+ * xdr_reset_scratch_buffer - Clear scratch buffer information
+ * @xdr: pointer to xdr_stream struct
+ *
+ * See xdr_set_scratch_buffer().
+ */
+static inline void
+xdr_reset_scratch_buffer(struct xdr_stream *xdr)
+{
+	xdr_set_scratch_buffer(xdr, NULL, 0);
+}
+
 /**
  * xdr_stream_remaining - Return the number of bytes remaining in the stream
  * @xdr: pointer to struct xdr_stream

net/sunrpc/auth_gss/gss_rpc_xdr.c

@@ -789,7 +789,7 @@ int gssx_dec_accept_sec_context(struct rpc_rqst *rqstp,
 	scratch = alloc_page(GFP_KERNEL);
 	if (!scratch)
 		return -ENOMEM;
-	xdr_set_scratch_buffer(xdr, page_address(scratch), PAGE_SIZE);
+	xdr_set_scratch_page(xdr, scratch);
 
 	/* res->status */
 	err = gssx_dec_status(xdr, &res->status);

net/sunrpc/xdr.c

@@ -669,7 +669,7 @@ void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p,
 	struct kvec *iov = buf->head;
 	int scratch_len = buf->buflen - buf->page_len - buf->tail[0].iov_len;
 
-	xdr_set_scratch_buffer(xdr, NULL, 0);
+	xdr_reset_scratch_buffer(xdr);
 	BUG_ON(scratch_len < 0);
 	xdr->buf = buf;
 	xdr->iov = iov;
@@ -713,7 +713,7 @@ inline void xdr_commit_encode(struct xdr_stream *xdr)
 	page = page_address(*xdr->page_ptr);
 	memcpy(xdr->scratch.iov_base, page, shift);
 	memmove(page, page + shift, (void *)xdr->p - page);
-	xdr->scratch.iov_len = 0;
+	xdr_reset_scratch_buffer(xdr);
 }
 EXPORT_SYMBOL_GPL(xdr_commit_encode);
 
@@ -743,8 +743,7 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 	 * the "scratch" iov to track any temporarily unused fragment of
 	 * space at the end of the previous buffer:
 	 */
-	xdr->scratch.iov_base = xdr->p;
-	xdr->scratch.iov_len = frag1bytes;
+	xdr_set_scratch_buffer(xdr, xdr->p, frag1bytes);
 	p = page_address(*xdr->page_ptr);
 	/*
 	 * Note this is where the next encode will start after we've
@@ -1052,8 +1051,7 @@ void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p,
 		     struct rpc_rqst *rqst)
 {
 	xdr->buf = buf;
-	xdr->scratch.iov_base = NULL;
-	xdr->scratch.iov_len = 0;
+	xdr_reset_scratch_buffer(xdr);
 	xdr->nwords = XDR_QUADLEN(buf->len);
 	if (buf->head[0].iov_len != 0)
 		xdr_set_iov(xdr, buf->head, buf->len);
@@ -1101,24 +1099,6 @@ static __be32 * __xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 	return p;
 }
 
-/**
- * xdr_set_scratch_buffer - Attach a scratch buffer for decoding data.
- * @xdr: pointer to xdr_stream struct
- * @buf: pointer to an empty buffer
- * @buflen: size of 'buf'
- *
- * The scratch buffer is used when decoding from an array of pages.
- * If an xdr_inline_decode() call spans across page boundaries, then
- * we copy the data into the scratch buffer in order to allow linear
- * access.
- */
-void xdr_set_scratch_buffer(struct xdr_stream *xdr, void *buf, size_t buflen)
-{
-	xdr->scratch.iov_base = buf;
-	xdr->scratch.iov_len = buflen;
-}
-EXPORT_SYMBOL_GPL(xdr_set_scratch_buffer);
-
 static __be32 *xdr_copy_to_scratch(struct xdr_stream *xdr, size_t nbytes)
 {
 	__be32 *p;