1 files changed, 1081 insertions, 328 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index e34f4ee7f2b6..70efc727a9cd 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * linux/net/sunrpc/xdr.c
  *
@@ -15,6 +16,11 @@
 #include <linux/errno.h>
 #include <linux/sunrpc/xdr.h>
 #include <linux/sunrpc/msg_prot.h>
+#include <linux/bvec.h>
+#include <trace/events/sunrpc.h>
+
+static void _copy_to_pages(struct page **, size_t, const char *, size_t);
+
 
 /*
  * XDR functions for basic NFS types
@@ -31,19 +37,6 @@ xdr_encode_netobj(__be32 *p, const struct xdr_netobj *obj)
 }
 EXPORT_SYMBOL_GPL(xdr_encode_netobj);
 
-__be32 *
-xdr_decode_netobj(__be32 *p, struct xdr_netobj *obj)
-{
-	unsigned int	len;
-
-	if ((len = be32_to_cpu(*p++)) > XDR_MAX_NETOBJ)
-		return NULL;
-	obj->len  = len;
-	obj->data = (u8 *) p;
-	return p + XDR_QUADLEN(len);
-}
-EXPORT_SYMBOL_GPL(xdr_decode_netobj);
-
 /**
  * xdr_encode_opaque_fixed - Encode fixed length opaque data
  * @p: pointer to current position in XDR buffer.
@@ -96,29 +89,13 @@ xdr_encode_string(__be32 *p, const char *string)
 }
 EXPORT_SYMBOL_GPL(xdr_encode_string);
 
-__be32 *
-xdr_decode_string_inplace(__be32 *p, char **sp,
-			  unsigned int *lenp, unsigned int maxlen)
-{
-	u32 len;
-
-	len = be32_to_cpu(*p++);
-	if (len > maxlen)
-		return NULL;
-	*lenp = len;
-	*sp = (char *) p;
-	return p + XDR_QUADLEN(len);
-}
-EXPORT_SYMBOL_GPL(xdr_decode_string_inplace);
-
 /**
  * xdr_terminate_string - '\0'-terminate a string residing in an xdr_buf
  * @buf: XDR buffer where string resides
  * @len: length of string, in bytes
  *
  */
-void
-xdr_terminate_string(struct xdr_buf *buf, const u32 len)
+void xdr_terminate_string(const struct xdr_buf *buf, const u32 len)
 {
 	char *kaddr;
 
@@ -128,6 +105,97 @@ xdr_terminate_string(struct xdr_buf *buf, const u32 len)
 }
 EXPORT_SYMBOL_GPL(xdr_terminate_string);
 
+size_t xdr_buf_pagecount(const struct xdr_buf *buf)
+{
+	if (!buf->page_len)
+		return 0;
+	return (buf->page_base + buf->page_len + PAGE_SIZE - 1) >> PAGE_SHIFT;
+}
+
+int
+xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp)
+{
+	size_t i, n = xdr_buf_pagecount(buf);
+
+	if (n != 0 && buf->bvec == NULL) {
+		buf->bvec = kmalloc_array(n, sizeof(buf->bvec[0]), gfp);
+		if (!buf->bvec)
+			return -ENOMEM;
+		for (i = 0; i < n; i++) {
+			bvec_set_page(&buf->bvec[i], buf->pages[i], PAGE_SIZE,
+				      0);
+		}
+	}
+	return 0;
+}
+
+void
+xdr_free_bvec(struct xdr_buf *buf)
+{
+	kfree(buf->bvec);
+	buf->bvec = NULL;
+}
+
+/**
+ * xdr_buf_to_bvec - Copy components of an xdr_buf into a bio_vec array
+ * @bvec: bio_vec array to populate
+ * @bvec_size: element count of @bio_vec
+ * @xdr: xdr_buf to be copied
+ *
+ * Returns the number of entries consumed in @bvec.
+ */
+unsigned int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size,
+			     const struct xdr_buf *xdr)
+{
+	const struct kvec *head = xdr->head;
+	const struct kvec *tail = xdr->tail;
+	unsigned int count = 0;
+
+	if (head->iov_len) {
+		bvec_set_virt(bvec++, head->iov_base, head->iov_len);
+		++count;
+	}
+
+	if (xdr->page_len) {
+		unsigned int offset, len, remaining;
+		struct page **pages = xdr->pages;
+
+		offset = offset_in_page(xdr->page_base);
+		remaining = xdr->page_len;
+		while (remaining > 0) {
+			len = min_t(unsigned int, remaining,
+				    PAGE_SIZE - offset);
+			bvec_set_page(bvec++, *pages++, len, offset);
+			remaining -= len;
+			offset = 0;
+			if (unlikely(++count > bvec_size))
+				goto bvec_overflow;
+		}
+	}
+
+	if (tail->iov_len) {
+		bvec_set_virt(bvec, tail->iov_base, tail->iov_len);
+		if (unlikely(++count > bvec_size))
+			goto bvec_overflow;
+	}
+
+	return count;
+
+bvec_overflow:
+	pr_warn_once("%s: bio_vec array overflow\n", __func__);
+	return count - 1;
+}
+EXPORT_SYMBOL_GPL(xdr_buf_to_bvec);
+
+/**
+ * xdr_inline_pages - Prepare receive buffer for a large reply
+ * @xdr: xdr_buf into which reply will be placed
+ * @offset: expected offset where data payload will start, in bytes
+ * @pages: vector of struct page pointers
+ * @base: offset in first page where receive should start, in bytes
+ * @len: expected size of the upper layer data payload, in bytes
+ *
+ */
 void
 xdr_inline_pages(struct xdr_buf *xdr, unsigned int offset,
 		 struct page **pages, unsigned int base, unsigned int len)
@@ -145,7 +213,6 @@ xdr_inline_pages(struct xdr_buf *xdr, unsigned int offset,
 
 	tail->iov_base = buf + offset;
 	tail->iov_len = buflen - offset;
-
 	xdr->buflen += len;
 }
 EXPORT_SYMBOL_GPL(xdr_inline_pages);
@@ -155,6 +222,71 @@ EXPORT_SYMBOL_GPL(xdr_inline_pages);
  */
 
 /**
+ * _shift_data_left_pages
+ * @pages: vector of pages containing both the source and dest memory area.
+ * @pgto_base: page vector address of destination
+ * @pgfrom_base: page vector address of source
+ * @len: number of bytes to copy
+ *
+ * Note: the addresses pgto_base and pgfrom_base are both calculated in
+ *       the same way:
+ *            if a memory area starts at byte 'base' in page 'pages[i]',
+ *            then its address is given as (i << PAGE_CACHE_SHIFT) + base
+ * Alse note: pgto_base must be < pgfrom_base, but the memory areas
+ * 	they point to may overlap.
+ */
+static void
+_shift_data_left_pages(struct page **pages, size_t pgto_base,
+			size_t pgfrom_base, size_t len)
+{
+	struct page **pgfrom, **pgto;
+	char *vfrom, *vto;
+	size_t copy;
+
+	BUG_ON(pgfrom_base <= pgto_base);
+
+	if (!len)
+		return;
+
+	pgto = pages + (pgto_base >> PAGE_SHIFT);
+	pgfrom = pages + (pgfrom_base >> PAGE_SHIFT);
+
+	pgto_base &= ~PAGE_MASK;
+	pgfrom_base &= ~PAGE_MASK;
+
+	do {
+		if (pgto_base >= PAGE_SIZE) {
+			pgto_base = 0;
+			pgto++;
+		}
+		if (pgfrom_base >= PAGE_SIZE){
+			pgfrom_base = 0;
+			pgfrom++;
+		}
+
+		copy = len;
+		if (copy > (PAGE_SIZE - pgto_base))
+			copy = PAGE_SIZE - pgto_base;
+		if (copy > (PAGE_SIZE - pgfrom_base))
+			copy = PAGE_SIZE - pgfrom_base;
+
+		vto = kmap_atomic(*pgto);
+		if (*pgto != *pgfrom) {
+			vfrom = kmap_atomic(*pgfrom);
+			memcpy(vto + pgto_base, vfrom + pgfrom_base, copy);
+			kunmap_atomic(vfrom);
+		} else
+			memmove(vto + pgto_base, vto + pgfrom_base, copy);
+		flush_dcache_page(*pgto);
+		kunmap_atomic(vto);
+
+		pgto_base += copy;
+		pgfrom_base += copy;
+
+	} while ((len -= copy) != 0);
+}
+
+/**
  * _shift_data_right_pages
  * @pages: vector of pages containing both the source and dest memory area.
  * @pgto_base: page vector address of destination
@@ -178,6 +310,9 @@ _shift_data_right_pages(struct page **pages, size_t pgto_base,
 
 	BUG_ON(pgto_base <= pgfrom_base);
 
+	if (!len)
+		return;
+
 	pgto_base += len;
 	pgfrom_base += len;
 
@@ -236,6 +371,9 @@ _copy_to_pages(struct page **pages, size_t pgbase, const char *p, size_t len)
 	char *vto;
 	size_t copy;
 
+	if (!len)
+		return;
+
 	pgto = pages + (pgbase >> PAGE_SHIFT);
 	pgbase &= ~PAGE_MASK;
 
@@ -280,6 +418,9 @@ _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len)
 	char *vfrom;
 	size_t copy;
 
+	if (!len)
+		return;
+
 	pgfrom = pages + (pgbase >> PAGE_SHIFT);
 	pgbase &= ~PAGE_MASK;
 
@@ -303,136 +444,446 @@ _copy_from_pages(char *p, struct page **pages, size_t pgbase, size_t len)
 }
 EXPORT_SYMBOL_GPL(_copy_from_pages);
 
+static void xdr_buf_iov_zero(const struct kvec *iov, unsigned int base,
+			     unsigned int len)
+{
+	if (base >= iov->iov_len)
+		return;
+	if (len > iov->iov_len - base)
+		len = iov->iov_len - base;
+	memset(iov->iov_base + base, 0, len);
+}
+
 /**
- * xdr_shrink_bufhead
+ * xdr_buf_pages_zero
  * @buf: xdr_buf
- * @len: bytes to remove from buf->head[0]
- *
- * Shrinks XDR buffer's header kvec buf->head[0] by
- * 'len' bytes. The extra data is not lost, but is instead
- * moved into the inlined pages and/or the tail.
+ * @pgbase: beginning offset
+ * @len: length
  */
-static void
-xdr_shrink_bufhead(struct xdr_buf *buf, size_t len)
+static void xdr_buf_pages_zero(const struct xdr_buf *buf, unsigned int pgbase,
+			       unsigned int len)
 {
-	struct kvec *head, *tail;
-	size_t copy, offs;
-	unsigned int pglen = buf->page_len;
+	struct page **pages = buf->pages;
+	struct page **page;
+	char *vpage;
+	unsigned int zero;
+
+	if (!len)
+		return;
+	if (pgbase >= buf->page_len) {
+		xdr_buf_iov_zero(buf->tail, pgbase - buf->page_len, len);
+		return;
+	}
+	if (pgbase + len > buf->page_len) {
+		xdr_buf_iov_zero(buf->tail, 0, pgbase + len - buf->page_len);
+		len = buf->page_len - pgbase;
+	}
 
-	tail = buf->tail;
-	head = buf->head;
+	pgbase += buf->page_base;
 
-	WARN_ON_ONCE(len > head->iov_len);
-	if (len > head->iov_len)
-		len = head->iov_len;
-
-	/* Shift the tail first */
-	if (tail->iov_len != 0) {
-		if (tail->iov_len > len) {
-			copy = tail->iov_len - len;
-			memmove((char *)tail->iov_base + len,
-					tail->iov_base, copy);
+	page = pages + (pgbase >> PAGE_SHIFT);
+	pgbase &= ~PAGE_MASK;
+
+	do {
+		zero = PAGE_SIZE - pgbase;
+		if (zero > len)
+			zero = len;
+
+		vpage = kmap_atomic(*page);
+		memset(vpage + pgbase, 0, zero);
+		kunmap_atomic(vpage);
+
+		flush_dcache_page(*page);
+		pgbase = 0;
+		page++;
+
+	} while ((len -= zero) != 0);
+}
+
+static unsigned int xdr_buf_pages_fill_sparse(const struct xdr_buf *buf,
+					      unsigned int buflen, gfp_t gfp)
+{
+	unsigned int i, npages, pagelen;
+
+	if (!(buf->flags & XDRBUF_SPARSE_PAGES))
+		return buflen;
+	if (buflen <= buf->head->iov_len)
+		return buflen;
+	pagelen = buflen - buf->head->iov_len;
+	if (pagelen > buf->page_len)
+		pagelen = buf->page_len;
+	npages = (pagelen + buf->page_base + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	for (i = 0; i < npages; i++) {
+		if (!buf->pages[i])
+			continue;
+		buf->pages[i] = alloc_page(gfp);
+		if (likely(buf->pages[i]))
+			continue;
+		buflen -= pagelen;
+		pagelen = i << PAGE_SHIFT;
+		if (pagelen > buf->page_base)
+			buflen += pagelen - buf->page_base;
+		break;
+	}
+	return buflen;
+}
+
+static void xdr_buf_try_expand(struct xdr_buf *buf, unsigned int len)
+{
+	struct kvec *head = buf->head;
+	struct kvec *tail = buf->tail;
+	unsigned int sum = head->iov_len + buf->page_len + tail->iov_len;
+	unsigned int free_space, newlen;
+
+	if (sum > buf->len) {
+		free_space = min_t(unsigned int, sum - buf->len, len);
+		newlen = xdr_buf_pages_fill_sparse(buf, buf->len + free_space,
+						   GFP_KERNEL);
+		free_space = newlen - buf->len;
+		buf->len = newlen;
+		len -= free_space;
+		if (!len)
+			return;
+	}
+
+	if (buf->buflen > sum) {
+		/* Expand the tail buffer */
+		free_space = min_t(unsigned int, buf->buflen - sum, len);
+		tail->iov_len += free_space;
+		buf->len += free_space;
+	}
+}
+
+static void xdr_buf_tail_copy_right(const struct xdr_buf *buf,
+				    unsigned int base, unsigned int len,
+				    unsigned int shift)
+{
+	const struct kvec *tail = buf->tail;
+	unsigned int to = base + shift;
+
+	if (to >= tail->iov_len)
+		return;
+	if (len + to > tail->iov_len)
+		len = tail->iov_len - to;
+	memmove(tail->iov_base + to, tail->iov_base + base, len);
+}
+
+static void xdr_buf_pages_copy_right(const struct xdr_buf *buf,
+				     unsigned int base, unsigned int len,
+				     unsigned int shift)
+{
+	const struct kvec *tail = buf->tail;
+	unsigned int to = base + shift;
+	unsigned int pglen = 0;
+	unsigned int talen = 0, tato = 0;
+
+	if (base >= buf->page_len)
+		return;
+	if (len > buf->page_len - base)
+		len = buf->page_len - base;
+	if (to >= buf->page_len) {
+		tato = to - buf->page_len;
+		if (tail->iov_len >= len + tato)
+			talen = len;
+		else if (tail->iov_len > tato)
+			talen = tail->iov_len - tato;
+	} else if (len + to >= buf->page_len) {
+		pglen = buf->page_len - to;
+		talen = len - pglen;
+		if (talen > tail->iov_len)
+			talen = tail->iov_len;
+	} else
+		pglen = len;
+
+	_copy_from_pages(tail->iov_base + tato, buf->pages,
+			 buf->page_base + base + pglen, talen);
+	_shift_data_right_pages(buf->pages, buf->page_base + to,
+				buf->page_base + base, pglen);
+}
+
+static void xdr_buf_head_copy_right(const struct xdr_buf *buf,
+				    unsigned int base, unsigned int len,
+				    unsigned int shift)
+{
+	const struct kvec *head = buf->head;
+	const struct kvec *tail = buf->tail;
+	unsigned int to = base + shift;
+	unsigned int pglen = 0, pgto = 0;
+	unsigned int talen = 0, tato = 0;
+
+	if (base >= head->iov_len)
+		return;
+	if (len > head->iov_len - base)
+		len = head->iov_len - base;
+	if (to >= buf->page_len + head->iov_len) {
+		tato = to - buf->page_len - head->iov_len;
+		talen = len;
+	} else if (to >= head->iov_len) {
+		pgto = to - head->iov_len;
+		pglen = len;
+		if (pgto + pglen > buf->page_len) {
+			talen = pgto + pglen - buf->page_len;
+			pglen -= talen;
 		}
-		/* Copy from the inlined pages into the tail */
-		copy = len;
-		if (copy > pglen)
-			copy = pglen;
-		offs = len - copy;
-		if (offs >= tail->iov_len)
-			copy = 0;
-		else if (copy > tail->iov_len - offs)
-			copy = tail->iov_len - offs;
-		if (copy != 0)
-			_copy_from_pages((char *)tail->iov_base + offs,
-					buf->pages,
-					buf->page_base + pglen + offs - len,
-					copy);
-		/* Do we also need to copy data from the head into the tail ? */
-		if (len > pglen) {
-			offs = copy = len - pglen;
-			if (copy > tail->iov_len)
-				copy = tail->iov_len;
-			memcpy(tail->iov_base,
-					(char *)head->iov_base +
-					head->iov_len - offs,
-					copy);
+	} else {
+		pglen = len - to;
+		if (pglen > buf->page_len) {
+			talen = pglen - buf->page_len;
+			pglen = buf->page_len;
 		}
 	}
-	/* Now handle pages */
-	if (pglen != 0) {
-		if (pglen > len)
-			_shift_data_right_pages(buf->pages,
-					buf->page_base + len,
-					buf->page_base,
-					pglen - len);
-		copy = len;
-		if (len > pglen)
-			copy = pglen;
-		_copy_to_pages(buf->pages, buf->page_base,
-				(char *)head->iov_base + head->iov_len - len,
-				copy);
+
+	len -= talen;
+	base += len;
+	if (talen + tato > tail->iov_len)
+		talen = tail->iov_len > tato ? tail->iov_len - tato : 0;
+	memcpy(tail->iov_base + tato, head->iov_base + base, talen);
+
+	len -= pglen;
+	base -= pglen;
+	_copy_to_pages(buf->pages, buf->page_base + pgto, head->iov_base + base,
+		       pglen);
+
+	base -= len;
+	memmove(head->iov_base + to, head->iov_base + base, len);
+}
+
+static void xdr_buf_tail_shift_right(const struct xdr_buf *buf,
+				     unsigned int base, unsigned int len,
+				     unsigned int shift)
+{
+	const struct kvec *tail = buf->tail;
+
+	if (base >= tail->iov_len || !shift || !len)
+		return;
+	xdr_buf_tail_copy_right(buf, base, len, shift);
+}
+
+static void xdr_buf_pages_shift_right(const struct xdr_buf *buf,
+				      unsigned int base, unsigned int len,
+				      unsigned int shift)
+{
+	if (!shift || !len)
+		return;
+	if (base >= buf->page_len) {
+		xdr_buf_tail_shift_right(buf, base - buf->page_len, len, shift);
+		return;
+	}
+	if (base + len > buf->page_len)
+		xdr_buf_tail_shift_right(buf, 0, base + len - buf->page_len,
+					 shift);
+	xdr_buf_pages_copy_right(buf, base, len, shift);
+}
+
+static void xdr_buf_head_shift_right(const struct xdr_buf *buf,
+				     unsigned int base, unsigned int len,
+				     unsigned int shift)
+{
+	const struct kvec *head = buf->head;
+
+	if (!shift)
+		return;
+	if (base >= head->iov_len) {
+		xdr_buf_pages_shift_right(buf, head->iov_len - base, len,
+					  shift);
+		return;
+	}
+	if (base + len > head->iov_len)
+		xdr_buf_pages_shift_right(buf, 0, base + len - head->iov_len,
+					  shift);
+	xdr_buf_head_copy_right(buf, base, len, shift);
+}
+
+static void xdr_buf_tail_copy_left(const struct xdr_buf *buf, unsigned int base,
+				   unsigned int len, unsigned int shift)
+{
+	const struct kvec *tail = buf->tail;
+
+	if (base >= tail->iov_len)
+		return;
+	if (len > tail->iov_len - base)
+		len = tail->iov_len - base;
+	/* Shift data into head */
+	if (shift > buf->page_len + base) {
+		const struct kvec *head = buf->head;
+		unsigned int hdto =
+			head->iov_len + buf->page_len + base - shift;
+		unsigned int hdlen = len;
+
+		if (WARN_ONCE(shift > head->iov_len + buf->page_len + base,
+			      "SUNRPC: Misaligned data.\n"))
+			return;
+		if (hdto + hdlen > head->iov_len)
+			hdlen = head->iov_len - hdto;
+		memcpy(head->iov_base + hdto, tail->iov_base + base, hdlen);
+		base += hdlen;
+		len -= hdlen;
+		if (!len)
+			return;
+	}
+	/* Shift data into pages */
+	if (shift > base) {
+		unsigned int pgto = buf->page_len + base - shift;
+		unsigned int pglen = len;
+
+		if (pgto + pglen > buf->page_len)
+			pglen = buf->page_len - pgto;
+		_copy_to_pages(buf->pages, buf->page_base + pgto,
+			       tail->iov_base + base, pglen);
+		base += pglen;
+		len -= pglen;
+		if (!len)
+			return;
+	}
+	memmove(tail->iov_base + base - shift, tail->iov_base + base, len);
+}
+
+static void xdr_buf_pages_copy_left(const struct xdr_buf *buf,
+				    unsigned int base, unsigned int len,
+				    unsigned int shift)
+{
+	unsigned int pgto;
+
+	if (base >= buf->page_len)
+		return;
+	if (len > buf->page_len - base)
+		len = buf->page_len - base;
+	/* Shift data into head */
+	if (shift > base) {
+		const struct kvec *head = buf->head;
+		unsigned int hdto = head->iov_len + base - shift;
+		unsigned int hdlen = len;
+
+		if (WARN_ONCE(shift > head->iov_len + base,
+			      "SUNRPC: Misaligned data.\n"))
+			return;
+		if (hdto + hdlen > head->iov_len)
+			hdlen = head->iov_len - hdto;
+		_copy_from_pages(head->iov_base + hdto, buf->pages,
+				 buf->page_base + base, hdlen);
+		base += hdlen;
+		len -= hdlen;
+		if (!len)
+			return;
 	}
-	head->iov_len -= len;
-	buf->buflen -= len;
-	/* Have we truncated the message? */
-	if (buf->len > buf->buflen)
-		buf->len = buf->buflen;
+	pgto = base - shift;
+	_shift_data_left_pages(buf->pages, buf->page_base + pgto,
+			       buf->page_base + base, len);
+}
+
+static void xdr_buf_tail_shift_left(const struct xdr_buf *buf,
+				    unsigned int base, unsigned int len,
+				    unsigned int shift)
+{
+	if (!shift || !len)
+		return;
+	xdr_buf_tail_copy_left(buf, base, len, shift);
+}
+
+static void xdr_buf_pages_shift_left(const struct xdr_buf *buf,
+				     unsigned int base, unsigned int len,
+				     unsigned int shift)
+{
+	if (!shift || !len)
+		return;
+	if (base >= buf->page_len) {
+		xdr_buf_tail_shift_left(buf, base - buf->page_len, len, shift);
+		return;
+	}
+	xdr_buf_pages_copy_left(buf, base, len, shift);
+	len += base;
+	if (len <= buf->page_len)
+		return;
+	xdr_buf_tail_copy_left(buf, 0, len - buf->page_len, shift);
+}
+
+static void xdr_buf_head_shift_left(const struct xdr_buf *buf,
+				    unsigned int base, unsigned int len,
+				    unsigned int shift)
+{
+	const struct kvec *head = buf->head;
+	unsigned int bytes;
+
+	if (!shift || !len)
+		return;
+
+	if (shift > base) {
+		bytes = (shift - base);
+		if (bytes >= len)
+			return;
+		base += bytes;
+		len -= bytes;
+	}
+
+	if (base < head->iov_len) {
+		bytes = min_t(unsigned int, len, head->iov_len - base);
+		memmove(head->iov_base + (base - shift),
+			head->iov_base + base, bytes);
+		base += bytes;
+		len -= bytes;
+	}
+	xdr_buf_pages_shift_left(buf, base - head->iov_len, len, shift);
 }
 
 /**
- * xdr_shrink_pagelen
+ * xdr_shrink_bufhead
  * @buf: xdr_buf
- * @len: bytes to remove from buf->pages
+ * @len: new length of buf->head[0]
  *
- * Shrinks XDR buffer's page array buf->pages by
+ * Shrinks XDR buffer's header kvec buf->head[0], setting it to
  * 'len' bytes. The extra data is not lost, but is instead
- * moved into the tail.
+ * moved into the inlined pages and/or the tail.
  */
-static void
-xdr_shrink_pagelen(struct xdr_buf *buf, size_t len)
+static unsigned int xdr_shrink_bufhead(struct xdr_buf *buf, unsigned int len)
 {
-	struct kvec *tail;
-	size_t copy;
-	unsigned int pglen = buf->page_len;
-	unsigned int tailbuf_len;
-
-	tail = buf->tail;
-	BUG_ON (len > pglen);
-
-	tailbuf_len = buf->buflen - buf->head->iov_len - buf->page_len;
-
-	/* Shift the tail first */
-	if (tailbuf_len != 0) {
-		unsigned int free_space = tailbuf_len - tail->iov_len;
-
-		if (len < free_space)
-			free_space = len;
-		tail->iov_len += free_space;
+	struct kvec *head = buf->head;
+	unsigned int shift, buflen = max(buf->len, len);
 
-		copy = len;
-		if (tail->iov_len > len) {
-			char *p = (char *)tail->iov_base + len;
-			memmove(p, tail->iov_base, tail->iov_len - len);
-		} else
-			copy = tail->iov_len;
-		/* Copy from the inlined pages into the tail */
-		_copy_from_pages((char *)tail->iov_base,
-				buf->pages, buf->page_base + pglen - len,
-				copy);
+	WARN_ON_ONCE(len > head->iov_len);
+	if (head->iov_len > buflen) {
+		buf->buflen -= head->iov_len - buflen;
+		head->iov_len = buflen;
 	}
-	buf->page_len -= len;
-	buf->buflen -= len;
-	/* Have we truncated the message? */
-	if (buf->len > buf->buflen)
-		buf->len = buf->buflen;
+	if (len >= head->iov_len)
+		return 0;
+	shift = head->iov_len - len;
+	xdr_buf_try_expand(buf, shift);
+	xdr_buf_head_shift_right(buf, len, buflen - len, shift);
+	head->iov_len = len;
+	buf->buflen -= shift;
+	buf->len -= shift;
+	return shift;
 }
 
-void
-xdr_shift_buf(struct xdr_buf *buf, size_t len)
+/**
+ * xdr_shrink_pagelen - shrinks buf->pages to @len bytes
+ * @buf: xdr_buf
+ * @len: new page buffer length
+ *
+ * The extra data is not lost, but is instead moved into buf->tail.
+ * Returns the actual number of bytes moved.
+ */
+static unsigned int xdr_shrink_pagelen(struct xdr_buf *buf, unsigned int len)
 {
-	xdr_shrink_bufhead(buf, len);
+	unsigned int shift, buflen = buf->len - buf->head->iov_len;
+
+	WARN_ON_ONCE(len > buf->page_len);
+	if (buf->head->iov_len >= buf->len || len > buflen)
+		buflen = len;
+	if (buf->page_len > buflen) {
+		buf->buflen -= buf->page_len - buflen;
+		buf->page_len = buflen;
+	}
+	if (len >= buf->page_len)
+		return 0;
+	shift = buf->page_len - len;
+	xdr_buf_try_expand(buf, shift);
+	xdr_buf_pages_shift_right(buf, len, buflen - len, shift);
+	buf->page_len = len;
+	buf->len -= shift;
+	buf->buflen -= shift;
+	return shift;
 }
-EXPORT_SYMBOL_GPL(xdr_shift_buf);
 
 /**
  * xdr_stream_pos - Return the current offset from the start of the xdr_stream
@@ -444,11 +895,37 @@ unsigned int xdr_stream_pos(const struct xdr_stream *xdr)
 }
 EXPORT_SYMBOL_GPL(xdr_stream_pos);
 
+static void xdr_stream_set_pos(struct xdr_stream *xdr, unsigned int pos)
+{
+	unsigned int blen = xdr->buf->len;
+
+	xdr->nwords = blen > pos ? XDR_QUADLEN(blen) - XDR_QUADLEN(pos) : 0;
+}
+
+static void xdr_stream_page_set_pos(struct xdr_stream *xdr, unsigned int pos)
+{
+	xdr_stream_set_pos(xdr, pos + xdr->buf->head[0].iov_len);
+}
+
+/**
+ * xdr_page_pos - Return the current offset from the start of the xdr pages
+ * @xdr: pointer to struct xdr_stream
+ */
+unsigned int xdr_page_pos(const struct xdr_stream *xdr)
+{
+	unsigned int pos = xdr_stream_pos(xdr);
+
+	WARN_ON(pos < xdr->buf->head[0].iov_len);
+	return pos - xdr->buf->head[0].iov_len;
+}
+EXPORT_SYMBOL_GPL(xdr_page_pos);
+
 /**
  * xdr_init_encode - Initialize a struct xdr_stream for sending data.
  * @xdr: pointer to xdr_stream struct
  * @buf: pointer to XDR buffer in which to encode data
  * @p: current pointer inside XDR buffer
+ * @rqst: pointer to controlling rpc_rqst, for debugging
  *
  * Note: at the moment the RPC client only passes the length of our
  *	 scratch buffer in the xdr_buf's header kvec. Previously this
@@ -457,12 +934,13 @@ EXPORT_SYMBOL_GPL(xdr_stream_pos);
  *	 of the buffer length, and takes care of adjusting the kvec
  *	 length for us.
  */
-void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p)
+void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p,
+		     struct rpc_rqst *rqst)
 {
 	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;
@@ -479,11 +957,31 @@ void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p)
 		buf->len += len;
 		iov->iov_len += len;
 	}
+	xdr->rqst = rqst;
 }
 EXPORT_SYMBOL_GPL(xdr_init_encode);
 
 /**
- * xdr_commit_encode - Ensure all data is written to buffer
+ * xdr_init_encode_pages - Initialize an xdr_stream for encoding into pages
+ * @xdr: pointer to xdr_stream struct
+ * @buf: pointer to XDR buffer into which to encode data
+ *
+ */
+void xdr_init_encode_pages(struct xdr_stream *xdr, struct xdr_buf *buf)
+{
+	xdr_reset_scratch_buffer(xdr);
+
+	xdr->buf = buf;
+	xdr->page_ptr = buf->pages;
+	xdr->iov = NULL;
+	xdr->p = page_address(*xdr->page_ptr);
+	xdr->end = (void *)xdr->p + min_t(u32, buf->buflen, PAGE_SIZE);
+	xdr->rqst = NULL;
+}
+EXPORT_SYMBOL_GPL(xdr_init_encode_pages);
+
+/**
+ * __xdr_commit_encode - Ensure all data is written to buffer
  * @xdr: pointer to xdr_stream
  *
  * We handle encoding across page boundaries by giving the caller a
@@ -495,31 +993,34 @@ EXPORT_SYMBOL_GPL(xdr_init_encode);
  * required at the end of encoding, or any other time when the xdr_buf
  * data might be read.
  */
-void xdr_commit_encode(struct xdr_stream *xdr)
+void __xdr_commit_encode(struct xdr_stream *xdr)
 {
-	int shift = xdr->scratch.iov_len;
+	size_t shift = xdr->scratch.iov_len;
 	void *page;
 
-	if (shift == 0)
-		return;
 	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);
+EXPORT_SYMBOL_GPL(__xdr_commit_encode);
 
-static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
-		size_t nbytes)
+/*
+ * The buffer space to be reserved crosses the boundary between
+ * xdr->buf->head and xdr->buf->pages, or between two pages
+ * in xdr->buf->pages.
+ */
+static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
+						   size_t nbytes)
 {
-	static __be32 *p;
 	int space_left;
 	int frag1bytes, frag2bytes;
+	void *p;
 
 	if (nbytes > PAGE_SIZE)
-		return NULL; /* Bigger buffers require special handling */
+		goto out_overflow; /* Bigger buffers require special handling */
 	if (xdr->buf->len + nbytes > xdr->buf->buflen)
-		return NULL; /* Sorry, we're totally out of space */
+		goto out_overflow; /* Sorry, we're totally out of space */
 	frag1bytes = (xdr->end - xdr->p) << 2;
 	frag2bytes = nbytes - frag1bytes;
 	if (xdr->iov)
@@ -528,6 +1029,7 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 		xdr->buf->page_len += frag1bytes;
 	xdr->page_ptr++;
 	xdr->iov = NULL;
+
 	/*
 	 * If the last encode didn't end exactly on a page boundary, the
 	 * next one will straddle boundaries.  Encode into the next
@@ -535,19 +1037,26 @@ 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;
-	p = page_address(*xdr->page_ptr);
+	xdr_set_scratch_buffer(xdr, xdr->p, frag1bytes);
+
 	/*
-	 * Note this is where the next encode will start after we've
-	 * shifted this one back:
+	 * xdr->p is where the next encode will start after
+	 * xdr_commit_encode() has shifted this one back:
 	 */
-	xdr->p = (void *)p + frag2bytes;
+	p = page_address(*xdr->page_ptr);
+	xdr->p = p + frag2bytes;
 	space_left = xdr->buf->buflen - xdr->buf->len;
-	xdr->end = (void *)p + min_t(int, space_left, PAGE_SIZE);
+	if (space_left - frag1bytes >= PAGE_SIZE)
+		xdr->end = p + PAGE_SIZE;
+	else
+		xdr->end = p + space_left - frag1bytes;
+
 	xdr->buf->page_len += frag2bytes;
 	xdr->buf->len += nbytes;
 	return p;
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 
 /**
@@ -558,6 +1067,12 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
  * Checks that we have enough buffer space to encode 'nbytes' more
  * bytes of data. If so, update the total xdr_buf length, and
  * adjust the length of the current kvec.
+ *
+ * The returned pointer is valid only until the next call to
+ * xdr_reserve_space() or xdr_commit_encode() on @xdr. The current
+ * implementation of this API guarantees that space reserved for a
+ * four-byte data item remains valid until @xdr is destroyed, but
+ * that might not always be true in the future.
  */
 __be32 * xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes)
 {
@@ -582,6 +1097,49 @@ __be32 * xdr_reserve_space(struct xdr_stream *xdr, size_t nbytes)
 EXPORT_SYMBOL_GPL(xdr_reserve_space);
 
 /**
+ * xdr_reserve_space_vec - Reserves a large amount of buffer space for sending
+ * @xdr: pointer to xdr_stream
+ * @nbytes: number of bytes to reserve
+ *
+ * The size argument passed to xdr_reserve_space() is determined based
+ * on the number of bytes remaining in the current page to avoid
+ * invalidating iov_base pointers when xdr_commit_encode() is called.
+ *
+ * Return values:
+ *   %0: success
+ *   %-EMSGSIZE: not enough space is available in @xdr
+ */
+int xdr_reserve_space_vec(struct xdr_stream *xdr, size_t nbytes)
+{
+	size_t thislen;
+	__be32 *p;
+
+	/*
+	 * svcrdma requires every READ payload to start somewhere
+	 * in xdr->pages.
+	 */
+	if (xdr->iov == xdr->buf->head) {
+		xdr->iov = NULL;
+		xdr->end = xdr->p;
+	}
+
+	/* XXX: Let's find a way to make this more efficient */
+	while (nbytes) {
+		thislen = xdr->buf->page_len % PAGE_SIZE;
+		thislen = min_t(size_t, nbytes, PAGE_SIZE - thislen);
+
+		p = xdr_reserve_space(xdr, thislen);
+		if (!p)
+			return -EMSGSIZE;
+
+		nbytes -= thislen;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(xdr_reserve_space_vec);
+
+/**
  * xdr_truncate_encode - truncate an encode buffer
  * @xdr: pointer to xdr_stream
  * @len: new length of buffer
@@ -591,7 +1149,7 @@ EXPORT_SYMBOL_GPL(xdr_reserve_space);
  * head, tail, and page lengths are adjusted to correspond.
  *
  * If this means moving xdr->p to a different buffer, we assume that
- * that the end pointer should be set to the end of the current page,
+ * the end pointer should be set to the end of the current page,
  * except in the case of the head buffer when we assume the head
  * buffer's current length represents the end of the available buffer.
  *
@@ -639,11 +1197,10 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len)
 		WARN_ON_ONCE(xdr->iov);
 		return;
 	}
-	if (fraglen) {
+	if (fraglen)
 		xdr->end = head->iov_base + head->iov_len;
-		xdr->page_ptr--;
-	}
 	/* (otherwise assume xdr->end is already set) */
+	xdr->page_ptr--;
 	head->iov_len = len;
 	buf->len = len;
 	xdr->p = head->iov_base + head->iov_len;
@@ -652,6 +1209,21 @@ void xdr_truncate_encode(struct xdr_stream *xdr, size_t len)
 EXPORT_SYMBOL(xdr_truncate_encode);
 
 /**
+ * xdr_truncate_decode - Truncate a decoding stream
+ * @xdr: pointer to struct xdr_stream
+ * @len: Number of bytes to remove
+ *
+ */
+void xdr_truncate_decode(struct xdr_stream *xdr, size_t len)
+{
+	unsigned int nbytes = xdr_align_size(len);
+
+	xdr->buf->len -= nbytes;
+	xdr->nwords -= XDR_QUADLEN(nbytes);
+}
+EXPORT_SYMBOL_GPL(xdr_truncate_decode);
+
+/**
  * xdr_restrict_buflen - decrease available buffer space
  * @xdr: pointer to xdr_stream
  * @newbuflen: new maximum number of bytes available
@@ -683,30 +1255,34 @@ EXPORT_SYMBOL(xdr_restrict_buflen);
 /**
  * xdr_write_pages - Insert a list of pages into an XDR buffer for sending
  * @xdr: pointer to xdr_stream
- * @pages: list of pages
- * @base: offset of first byte
- * @len: length of data in bytes
+ * @pages: array of pages to insert
+ * @base: starting offset of first data byte in @pages
+ * @len: number of data bytes in @pages to insert
  *
+ * After the @pages are added, the tail iovec is instantiated pointing to
+ * end of the head buffer, and the stream is set up to encode subsequent
+ * items into the tail.
  */
 void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int base,
 		 unsigned int len)
 {
 	struct xdr_buf *buf = xdr->buf;
-	struct kvec *iov = buf->tail;
+	struct kvec *tail = buf->tail;
+
 	buf->pages = pages;
 	buf->page_base = base;
 	buf->page_len = len;
 
-	iov->iov_base = (char *)xdr->p;
-	iov->iov_len  = 0;
-	xdr->iov = iov;
+	tail->iov_base = xdr->p;
+	tail->iov_len = 0;
+	xdr->iov = tail;
 
 	if (len & 3) {
 		unsigned int pad = 4 - (len & 3);
 
 		BUG_ON(xdr->p >= xdr->end);
-		iov->iov_base = (char *)xdr->p + (len & 3);
-		iov->iov_len  += pad;
+		tail->iov_base = (char *)xdr->p + (len & 3);
+		tail->iov_len += pad;
 		len += pad;
 		*xdr->p++ = 0;
 	}
@@ -715,19 +1291,39 @@ void xdr_write_pages(struct xdr_stream *xdr, struct page **pages, unsigned int b
 }
 EXPORT_SYMBOL_GPL(xdr_write_pages);
 
-static void xdr_set_iov(struct xdr_stream *xdr, struct kvec *iov,
-		unsigned int len)
+static unsigned int xdr_set_iov(struct xdr_stream *xdr, struct kvec *iov,
+				unsigned int base, unsigned int len)
 {
 	if (len > iov->iov_len)
 		len = iov->iov_len;
-	xdr->p = (__be32*)iov->iov_base;
+	if (unlikely(base > len))
+		base = len;
+	xdr->p = (__be32*)(iov->iov_base + base);
 	xdr->end = (__be32*)(iov->iov_base + len);
 	xdr->iov = iov;
 	xdr->page_ptr = NULL;
+	return len - base;
+}
+
+static unsigned int xdr_set_tail_base(struct xdr_stream *xdr,
+				      unsigned int base, unsigned int len)
+{
+	struct xdr_buf *buf = xdr->buf;
+
+	xdr_stream_set_pos(xdr, base + buf->page_len + buf->head->iov_len);
+	return xdr_set_iov(xdr, buf->tail, base, len);
 }
 
-static int xdr_set_page_base(struct xdr_stream *xdr,
-		unsigned int base, unsigned int len)
+static void xdr_stream_unmap_current_page(struct xdr_stream *xdr)
+{
+	if (xdr->page_kaddr) {
+		kunmap_local(xdr->page_kaddr);
+		xdr->page_kaddr = NULL;
+	}
+}
+
+static unsigned int xdr_set_page_base(struct xdr_stream *xdr,
+				      unsigned int base, unsigned int len)
 {
 	unsigned int pgnr;
 	unsigned int maxlen;
@@ -737,16 +1333,24 @@ static int xdr_set_page_base(struct xdr_stream *xdr,
 
 	maxlen = xdr->buf->page_len;
 	if (base >= maxlen)
-		return -EINVAL;
-	maxlen -= base;
+		return 0;
+	else
+		maxlen -= base;
 	if (len > maxlen)
 		len = maxlen;
 
+	xdr_stream_unmap_current_page(xdr);
+	xdr_stream_page_set_pos(xdr, base);
 	base += xdr->buf->page_base;
 
 	pgnr = base >> PAGE_SHIFT;
 	xdr->page_ptr = &xdr->buf->pages[pgnr];
-	kaddr = page_address(*xdr->page_ptr);
+
+	if (PageHighMem(*xdr->page_ptr)) {
+		xdr->page_kaddr = kmap_local_page(*xdr->page_ptr);
+		kaddr = xdr->page_kaddr;
+	} else
+		kaddr = page_address(*xdr->page_ptr);
 
 	pgoff = base & ~PAGE_MASK;
 	xdr->p = (__be32*)(kaddr + pgoff);
@@ -756,7 +1360,16 @@ static int xdr_set_page_base(struct xdr_stream *xdr,
 		pgend = PAGE_SIZE;
 	xdr->end = (__be32*)(kaddr + pgend);
 	xdr->iov = NULL;
-	return 0;
+	return len;
+}
+
+static void xdr_set_page(struct xdr_stream *xdr, unsigned int base,
+			 unsigned int len)
+{
+	if (xdr_set_page_base(xdr, base, len) == 0) {
+		base -= xdr->buf->page_len;
+		xdr_set_tail_base(xdr, base, len);
+	}
 }
 
 static void xdr_set_next_page(struct xdr_stream *xdr)
@@ -765,19 +1378,18 @@ static void xdr_set_next_page(struct xdr_stream *xdr)
 
 	newbase = (1 + xdr->page_ptr - xdr->buf->pages) << PAGE_SHIFT;
 	newbase -= xdr->buf->page_base;
-
-	if (xdr_set_page_base(xdr, newbase, PAGE_SIZE) < 0)
-		xdr_set_iov(xdr, xdr->buf->tail, xdr->nwords << 2);
+	if (newbase < xdr->buf->page_len)
+		xdr_set_page_base(xdr, newbase, xdr_stream_remaining(xdr));
+	else
+		xdr_set_tail_base(xdr, 0, xdr_stream_remaining(xdr));
 }
 
 static bool xdr_set_next_buffer(struct xdr_stream *xdr)
 {
 	if (xdr->page_ptr != NULL)
 		xdr_set_next_page(xdr);
-	else if (xdr->iov == xdr->buf->head) {
-		if (xdr_set_page_base(xdr, 0, PAGE_SIZE) < 0)
-			xdr_set_iov(xdr, xdr->buf->tail, xdr->nwords << 2);
-	}
+	else if (xdr->iov == xdr->buf->head)
+		xdr_set_page(xdr, 0, xdr_stream_remaining(xdr));
 	return xdr->p != xdr->end;
 }
 
@@ -786,23 +1398,23 @@ static bool xdr_set_next_buffer(struct xdr_stream *xdr)
  * @xdr: pointer to xdr_stream struct
  * @buf: pointer to XDR buffer from which to decode data
  * @p: current pointer inside XDR buffer
+ * @rqst: pointer to controlling rpc_rqst, for debugging
  */
-void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p)
+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->page_kaddr = NULL;
+	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);
-	else if (buf->page_len != 0)
-		xdr_set_page_base(xdr, 0, buf->len);
-	else
-		xdr_set_iov(xdr, buf->head, buf->len);
+	if (xdr_set_iov(xdr, buf->head, 0, buf->len) == 0 &&
+	    xdr_set_page_base(xdr, 0, buf->len) == 0)
+		xdr_set_iov(xdr, buf->tail, 0, buf->len);
 	if (p != NULL && p > xdr->p && xdr->end >= p) {
 		xdr->nwords -= p - xdr->p;
 		xdr->p = p;
 	}
+	xdr->rqst = rqst;
 }
 EXPORT_SYMBOL_GPL(xdr_init_decode);
 
@@ -821,10 +1433,20 @@ void xdr_init_decode_pages(struct xdr_stream *xdr, struct xdr_buf *buf,
 	buf->page_len =  len;
 	buf->buflen =  len;
 	buf->len = len;
-	xdr_init_decode(xdr, buf, NULL);
+	xdr_init_decode(xdr, buf, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(xdr_init_decode_pages);
 
+/**
+ * xdr_finish_decode - Clean up the xdr_stream after decoding data.
+ * @xdr: pointer to xdr_stream struct
+ */
+void xdr_finish_decode(struct xdr_stream *xdr)
+{
+	xdr_stream_unmap_current_page(xdr);
+}
+EXPORT_SYMBOL(xdr_finish_decode);
+
 static __be32 * __xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 {
 	unsigned int nwords = XDR_QUADLEN(nbytes);
@@ -838,24 +1460,6 @@ 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;
@@ -863,20 +1467,23 @@ static __be32 *xdr_copy_to_scratch(struct xdr_stream *xdr, size_t nbytes)
 	size_t cplen = (char *)xdr->end - (char *)xdr->p;
 
 	if (nbytes > xdr->scratch.iov_len)
-		return NULL;
+		goto out_overflow;
 	p = __xdr_inline_decode(xdr, cplen);
 	if (p == NULL)
 		return NULL;
 	memcpy(cpdest, p, cplen);
+	if (!xdr_set_next_buffer(xdr))
+		goto out_overflow;
 	cpdest += cplen;
 	nbytes -= cplen;
-	if (!xdr_set_next_buffer(xdr))
-		return NULL;
 	p = __xdr_inline_decode(xdr, nbytes);
 	if (p == NULL)
 		return NULL;
 	memcpy(cpdest, p, nbytes);
 	return xdr->scratch.iov_base;
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 
 /**
@@ -893,33 +1500,45 @@ __be32 * xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes)
 {
 	__be32 *p;
 
-	if (nbytes == 0)
+	if (unlikely(nbytes == 0))
 		return xdr->p;
 	if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))
-		return NULL;
+		goto out_overflow;
 	p = __xdr_inline_decode(xdr, nbytes);
 	if (p != NULL)
 		return p;
 	return xdr_copy_to_scratch(xdr, nbytes);
+out_overflow:
+	trace_rpc_xdr_overflow(xdr, nbytes);
+	return NULL;
 }
 EXPORT_SYMBOL_GPL(xdr_inline_decode);
 
-static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
+static void xdr_realign_pages(struct xdr_stream *xdr)
 {
 	struct xdr_buf *buf = xdr->buf;
-	struct kvec *iov;
-	unsigned int nwords = XDR_QUADLEN(len);
+	struct kvec *iov = buf->head;
 	unsigned int cur = xdr_stream_pos(xdr);
+	unsigned int copied;
 
-	if (xdr->nwords == 0)
-		return 0;
 	/* Realign pages to current pointer position */
-	iov  = buf->head;
 	if (iov->iov_len > cur) {
-		xdr_shrink_bufhead(buf, iov->iov_len - cur);
-		xdr->nwords = XDR_QUADLEN(buf->len - cur);
+		copied = xdr_shrink_bufhead(buf, cur);
+		trace_rpc_xdr_alignment(xdr, cur, copied);
+		xdr_set_page(xdr, 0, buf->page_len);
 	}
+}
+
+static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
+{
+	struct xdr_buf *buf = xdr->buf;
+	unsigned int nwords = XDR_QUADLEN(len);
+	unsigned int copied;
+
+	if (xdr->nwords == 0)
+		return 0;
 
+	xdr_realign_pages(xdr);
 	if (nwords > xdr->nwords) {
 		nwords = xdr->nwords;
 		len = nwords << 2;
@@ -928,55 +1547,72 @@ static unsigned int xdr_align_pages(struct xdr_stream *xdr, unsigned int len)
 		len = buf->page_len;
 	else if (nwords < xdr->nwords) {
 		/* Truncate page data and move it into the tail */
-		xdr_shrink_pagelen(buf, buf->page_len - len);
-		xdr->nwords = XDR_QUADLEN(buf->len - cur);
+		copied = xdr_shrink_pagelen(buf, len);
+		trace_rpc_xdr_alignment(xdr, len, copied);
 	}
 	return len;
 }
 
 /**
- * xdr_read_pages - Ensure page-based XDR data to decode is aligned at current pointer position
+ * xdr_read_pages - align page-based XDR data to current pointer position
  * @xdr: pointer to xdr_stream struct
  * @len: number of bytes of page data
  *
  * Moves data beyond the current pointer position from the XDR head[] buffer
- * into the page list. Any data that lies beyond current position + "len"
- * bytes is moved into the XDR tail[].
+ * into the page list. Any data that lies beyond current position + @len
+ * bytes is moved into the XDR tail[]. The xdr_stream current position is
+ * then advanced past that data to align to the next XDR object in the tail.
  *
  * Returns the number of XDR encoded bytes now contained in the pages
  */
 unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
 {
-	struct xdr_buf *buf = xdr->buf;
-	struct kvec *iov;
-	unsigned int nwords;
-	unsigned int end;
-	unsigned int padding;
+	unsigned int nwords = XDR_QUADLEN(len);
+	unsigned int base, end, pglen;
 
-	len = xdr_align_pages(xdr, len);
-	if (len == 0)
+	pglen = xdr_align_pages(xdr, nwords << 2);
+	if (pglen == 0)
 		return 0;
-	nwords = XDR_QUADLEN(len);
-	padding = (nwords << 2) - len;
-	xdr->iov = iov = buf->tail;
-	/* Compute remaining message length.  */
-	end = ((xdr->nwords - nwords) << 2) + padding;
-	if (end > iov->iov_len)
-		end = iov->iov_len;
 
-	/*
-	 * Position current pointer at beginning of tail, and
-	 * set remaining message length.
-	 */
-	xdr->p = (__be32 *)((char *)iov->iov_base + padding);
-	xdr->end = (__be32 *)((char *)iov->iov_base + end);
-	xdr->page_ptr = NULL;
-	xdr->nwords = XDR_QUADLEN(end - padding);
-	return len;
+	base = (nwords << 2) - pglen;
+	end = xdr_stream_remaining(xdr) - pglen;
+
+	xdr_set_tail_base(xdr, base, end);
+	return len <= pglen ? len : pglen;
 }
 EXPORT_SYMBOL_GPL(xdr_read_pages);
 
 /**
+ * xdr_set_pagelen - Sets the length of the XDR pages
+ * @xdr: pointer to xdr_stream struct
+ * @len: new length of the XDR page data
+ *
+ * Either grows or shrinks the length of the xdr pages by setting pagelen to
+ * @len bytes. When shrinking, any extra data is moved into buf->tail, whereas
+ * when growing any data beyond the current pointer is moved into the tail.
+ *
+ * Returns True if the operation was successful, and False otherwise.
+ */
+void xdr_set_pagelen(struct xdr_stream *xdr, unsigned int len)
+{
+	struct xdr_buf *buf = xdr->buf;
+	size_t remaining = xdr_stream_remaining(xdr);
+	size_t base = 0;
+
+	if (len < buf->page_len) {
+		base = buf->page_len - len;
+		xdr_shrink_pagelen(buf, len);
+	} else {
+		xdr_buf_head_shift_right(buf, xdr_stream_pos(xdr),
+					 buf->page_len, remaining);
+		if (len > buf->page_len)
+			xdr_buf_try_expand(buf, len - buf->page_len);
+	}
+	xdr_set_tail_base(xdr, base, remaining);
+}
+EXPORT_SYMBOL_GPL(xdr_set_pagelen);
+
+/**
  * xdr_enter_page - decode data from the XDR page
  * @xdr: pointer to xdr_stream struct
  * @len: number of bytes of page data
@@ -998,10 +1634,9 @@ void xdr_enter_page(struct xdr_stream *xdr, unsigned int len)
 }
 EXPORT_SYMBOL_GPL(xdr_enter_page);
 
-static struct kvec empty_iov = {.iov_base = NULL, .iov_len = 0};
+static const struct kvec empty_iov = {.iov_base = NULL, .iov_len = 0};
 
-void
-xdr_buf_from_iov(struct kvec *iov, struct xdr_buf *buf)
+void xdr_buf_from_iov(const struct kvec *iov, struct xdr_buf *buf)
 {
 	buf->head[0] = *iov;
 	buf->tail[0] = empty_iov;
@@ -1022,11 +1657,10 @@ EXPORT_SYMBOL_GPL(xdr_buf_from_iov);
  *
  * @buf and @subbuf may be pointers to the same struct xdr_buf.
  *
- * Returns -1 if base of length are out of bounds.
+ * Returns -1 if base or length are out of bounds.
  */
-int
-xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
-			unsigned int base, unsigned int len)
+int xdr_buf_subsegment(const struct xdr_buf *buf, struct xdr_buf *subbuf,
+		       unsigned int base, unsigned int len)
 {
 	subbuf->buflen = subbuf->len = len;
 	if (base < buf->head[0].iov_len) {
@@ -1037,6 +1671,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->head[0].iov_len;
+		subbuf->head[0].iov_base = buf->head[0].iov_base;
 		subbuf->head[0].iov_len = 0;
 	}
 
@@ -1049,6 +1684,8 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->page_len;
+		subbuf->pages = buf->pages;
+		subbuf->page_base = 0;
 		subbuf->page_len = 0;
 	}
 
@@ -1060,6 +1697,7 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 		base = 0;
 	} else {
 		base -= buf->tail[0].iov_len;
+		subbuf->tail[0].iov_base = buf->tail[0].iov_base;
 		subbuf->tail[0].iov_len = 0;
 	}
 
@@ -1070,6 +1708,107 @@ xdr_buf_subsegment(struct xdr_buf *buf, struct xdr_buf *subbuf,
 EXPORT_SYMBOL_GPL(xdr_buf_subsegment);
 
 /**
+ * xdr_stream_subsegment - set @subbuf to a portion of @xdr
+ * @xdr: an xdr_stream set up for decoding
+ * @subbuf: the result buffer
+ * @nbytes: length of @xdr to extract, in bytes
+ *
+ * Sets up @subbuf to represent a portion of @xdr. The portion
+ * starts at the current offset in @xdr, and extends for a length
+ * of @nbytes. If this is successful, @xdr is advanced to the next
+ * XDR data item following that portion.
+ *
+ * Return values:
+ *   %true: @subbuf has been initialized, and @xdr has been advanced.
+ *   %false: a bounds error has occurred
+ */
+bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf,
+			   unsigned int nbytes)
+{
+	unsigned int start = xdr_stream_pos(xdr);
+	unsigned int remaining, len;
+
+	/* Extract @subbuf and bounds-check the fn arguments */
+	if (xdr_buf_subsegment(xdr->buf, subbuf, start, nbytes))
+		return false;
+
+	/* Advance @xdr by @nbytes */
+	for (remaining = nbytes; remaining;) {
+		if (xdr->p == xdr->end && !xdr_set_next_buffer(xdr))
+			return false;
+
+		len = (char *)xdr->end - (char *)xdr->p;
+		if (remaining <= len) {
+			xdr->p = (__be32 *)((char *)xdr->p +
+					(remaining + xdr_pad_size(nbytes)));
+			break;
+		}
+
+		xdr->p = (__be32 *)((char *)xdr->p + len);
+		xdr->end = xdr->p;
+		remaining -= len;
+	}
+
+	xdr_stream_set_pos(xdr, start + nbytes);
+	return true;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_subsegment);
+
+/**
+ * xdr_stream_move_subsegment - Move part of a stream to another position
+ * @xdr: the source xdr_stream
+ * @offset: the source offset of the segment
+ * @target: the target offset of the segment
+ * @length: the number of bytes to move
+ *
+ * Moves @length bytes from @offset to @target in the xdr_stream, overwriting
+ * anything in its space. Returns the number of bytes in the segment.
+ */
+unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset,
+					unsigned int target, unsigned int length)
+{
+	struct xdr_buf buf;
+	unsigned int shift;
+
+	if (offset < target) {
+		shift = target - offset;
+		if (xdr_buf_subsegment(xdr->buf, &buf, offset, shift + length) < 0)
+			return 0;
+		xdr_buf_head_shift_right(&buf, 0, length, shift);
+	} else if (offset > target) {
+		shift = offset - target;
+		if (xdr_buf_subsegment(xdr->buf, &buf, target, shift + length) < 0)
+			return 0;
+		xdr_buf_head_shift_left(&buf, shift, length, shift);
+	}
+	return length;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_move_subsegment);
+
+/**
+ * xdr_stream_zero - zero out a portion of an xdr_stream
+ * @xdr: an xdr_stream to zero out
+ * @offset: the starting point in the stream
+ * @length: the number of bytes to zero
+ */
+unsigned int xdr_stream_zero(struct xdr_stream *xdr, unsigned int offset,
+			     unsigned int length)
+{
+	struct xdr_buf buf;
+
+	if (xdr_buf_subsegment(xdr->buf, &buf, offset, length) < 0)
+		return 0;
+	if (buf.head[0].iov_len)
+		xdr_buf_iov_zero(buf.head, 0, buf.head[0].iov_len);
+	if (buf.page_len > 0)
+		xdr_buf_pages_zero(&buf, 0, buf.page_len);
+	if (buf.tail[0].iov_len)
+		xdr_buf_iov_zero(buf.tail, 0, buf.tail[0].iov_len);
+	return length;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_zero);
+
+/**
  * xdr_buf_trim - lop at most "len" bytes off the end of "buf"
  * @buf: buf to be trimmed
  * @len: number of bytes to reduce "buf" by
@@ -1110,7 +1849,8 @@ fix_len:
 }
 EXPORT_SYMBOL_GPL(xdr_buf_trim);
 
-static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len)
+static void __read_bytes_from_xdr_buf(const struct xdr_buf *subbuf,
+				      void *obj, unsigned int len)
 {
 	unsigned int this_len;
 
@@ -1119,8 +1859,7 @@ static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigne
 	len -= this_len;
 	obj += this_len;
 	this_len = min_t(unsigned int, len, subbuf->page_len);
-	if (this_len)
-		_copy_from_pages(obj, subbuf->pages, subbuf->page_base, this_len);
+	_copy_from_pages(obj, subbuf->pages, subbuf->page_base, this_len);
 	len -= this_len;
 	obj += this_len;
 	this_len = min_t(unsigned int, len, subbuf->tail[0].iov_len);
@@ -1128,7 +1867,8 @@ static void __read_bytes_from_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigne
 }
 
 /* obj is assumed to point to allocated memory of size at least len: */
-int read_bytes_from_xdr_buf(struct xdr_buf *buf, unsigned int base, void *obj, unsigned int len)
+int read_bytes_from_xdr_buf(const struct xdr_buf *buf, unsigned int base,
+			    void *obj, unsigned int len)
 {
 	struct xdr_buf subbuf;
 	int status;
@@ -1141,7 +1881,8 @@ int read_bytes_from_xdr_buf(struct xdr_buf *buf, unsigned int base, void *obj, u
 }
 EXPORT_SYMBOL_GPL(read_bytes_from_xdr_buf);
 
-static void __write_bytes_to_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned int len)
+static void __write_bytes_to_xdr_buf(const struct xdr_buf *subbuf,
+				     void *obj, unsigned int len)
 {
 	unsigned int this_len;
 
@@ -1150,8 +1891,7 @@ static void __write_bytes_to_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned
 	len -= this_len;
 	obj += this_len;
 	this_len = min_t(unsigned int, len, subbuf->page_len);
-	if (this_len)
-		_copy_to_pages(subbuf->pages, subbuf->page_base, obj, this_len);
+	_copy_to_pages(subbuf->pages, subbuf->page_base, obj, this_len);
 	len -= this_len;
 	obj += this_len;
 	this_len = min_t(unsigned int, len, subbuf->tail[0].iov_len);
@@ -1159,7 +1899,8 @@ static void __write_bytes_to_xdr_buf(struct xdr_buf *subbuf, void *obj, unsigned
 }
 
 /* obj is assumed to point to allocated memory of size at least len: */
-int write_bytes_to_xdr_buf(struct xdr_buf *buf, unsigned int base, void *obj, unsigned int len)
+int write_bytes_to_xdr_buf(const struct xdr_buf *buf, unsigned int base,
+			   void *obj, unsigned int len)
 {
 	struct xdr_buf subbuf;
 	int status;
@@ -1172,8 +1913,7 @@ int write_bytes_to_xdr_buf(struct xdr_buf *buf, unsigned int base, void *obj, un
 }
 EXPORT_SYMBOL_GPL(write_bytes_to_xdr_buf);
 
-int
-xdr_decode_word(struct xdr_buf *buf, unsigned int base, u32 *obj)
+int xdr_decode_word(const struct xdr_buf *buf, unsigned int base, u32 *obj)
 {
 	__be32	raw;
 	int	status;
@@ -1186,8 +1926,7 @@ xdr_decode_word(struct xdr_buf *buf, unsigned int base, u32 *obj)
 }
 EXPORT_SYMBOL_GPL(xdr_decode_word);
 
-int
-xdr_encode_word(struct xdr_buf *buf, unsigned int base, u32 obj)
+int xdr_encode_word(const struct xdr_buf *buf, unsigned int base, u32 obj)
 {
 	__be32	raw = cpu_to_be32(obj);
 
@@ -1195,48 +1934,9 @@ xdr_encode_word(struct xdr_buf *buf, unsigned int base, u32 obj)
 }
 EXPORT_SYMBOL_GPL(xdr_encode_word);
 
-/* If the netobj starting offset bytes from the start of xdr_buf is contained
- * entirely in the head or the tail, set object to point to it; otherwise
- * try to find space for it at the end of the tail, copy it there, and
- * set obj to point to it. */
-int xdr_buf_read_netobj(struct xdr_buf *buf, struct xdr_netobj *obj, unsigned int offset)
-{
-	struct xdr_buf subbuf;
-
-	if (xdr_decode_word(buf, offset, &obj->len))
-		return -EFAULT;
-	if (xdr_buf_subsegment(buf, &subbuf, offset + 4, obj->len))
-		return -EFAULT;
-
-	/* Is the obj contained entirely in the head? */
-	obj->data = subbuf.head[0].iov_base;
-	if (subbuf.head[0].iov_len == obj->len)
-		return 0;
-	/* ..or is the obj contained entirely in the tail? */
-	obj->data = subbuf.tail[0].iov_base;
-	if (subbuf.tail[0].iov_len == obj->len)
-		return 0;
-
-	/* use end of tail as storage for obj:
-	 * (We don't copy to the beginning because then we'd have
-	 * to worry about doing a potentially overlapping copy.
-	 * This assumes the object is at most half the length of the
-	 * tail.) */
-	if (obj->len > buf->buflen - buf->len)
-		return -ENOMEM;
-	if (buf->tail[0].iov_len != 0)
-		obj->data = buf->tail[0].iov_base + buf->tail[0].iov_len;
-	else
-		obj->data = buf->head[0].iov_base + buf->head[0].iov_len;
-	__read_bytes_from_xdr_buf(&subbuf, obj->data, obj->len);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(xdr_buf_read_netobj);
-
 /* Returns 0 on success, or else a negative error code. */
-static int
-xdr_xcode_array2(struct xdr_buf *buf, unsigned int base,
-		 struct xdr_array2_desc *desc, int encode)
+static int xdr_xcode_array2(const struct xdr_buf *buf, unsigned int base,
+			    struct xdr_array2_desc *desc, int encode)
 {
 	char *elem = NULL, *c;
 	unsigned int copied = 0, todo, avail_here;
@@ -1428,9 +2128,8 @@ out:
 	return err;
 }
 
-int
-xdr_decode_array2(struct xdr_buf *buf, unsigned int base,
-		  struct xdr_array2_desc *desc)
+int xdr_decode_array2(const struct xdr_buf *buf, unsigned int base,
+		      struct xdr_array2_desc *desc)
 {
 	if (base >= buf->len)
 		return -EINVAL;
@@ -1439,9 +2138,8 @@ xdr_decode_array2(struct xdr_buf *buf, unsigned int base,
 }
 EXPORT_SYMBOL_GPL(xdr_decode_array2);
 
-int
-xdr_encode_array2(struct xdr_buf *buf, unsigned int base,
-		  struct xdr_array2_desc *desc)
+int xdr_encode_array2(const struct xdr_buf *buf, unsigned int base,
+		      struct xdr_array2_desc *desc)
 {
 	if ((unsigned long) base + 4 + desc->array_len * desc->elem_size >
 	    buf->head->iov_len + buf->page_len + buf->tail->iov_len)
@@ -1451,9 +2149,9 @@ xdr_encode_array2(struct xdr_buf *buf, unsigned int base,
 }
 EXPORT_SYMBOL_GPL(xdr_encode_array2);
 
-int
-xdr_process_buf(struct xdr_buf *buf, unsigned int offset, unsigned int len,
-		int (*actor)(struct scatterlist *, void *), void *data)
+int xdr_process_buf(const struct xdr_buf *buf, unsigned int offset,
+		    unsigned int len,
+		    int (*actor)(struct scatterlist *, void *), void *data)
 {
 	int i, ret = 0;
 	unsigned int page_len, thislen, page_offset;
@@ -1539,10 +2237,8 @@ ssize_t xdr_stream_decode_string_dup(struct xdr_stream *xdr, char **str,
 
 	ret = xdr_stream_decode_opaque_inline(xdr, &p, maxlen);
 	if (ret > 0) {
-		char *s = kmalloc(ret + 1, gfp_flags);
+		char *s = kmemdup_nul(p, ret, gfp_flags);
 		if (s != NULL) {
-			memcpy(s, p, ret);
-			s[ret] = '\0';
 			*str = s;
 			return strlen(s);
 		}
@@ -1552,3 +2248,60 @@ ssize_t xdr_stream_decode_string_dup(struct xdr_stream *xdr, char **str,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(xdr_stream_decode_string_dup);
+
+/**
+ * xdr_stream_decode_opaque_auth - Decode struct opaque_auth (RFC5531 S8.2)
+ * @xdr: pointer to xdr_stream
+ * @flavor: location to store decoded flavor
+ * @body: location to store decode body
+ * @body_len: location to store length of decoded body
+ *
+ * Return values:
+ *   On success, returns the number of buffer bytes consumed
+ *   %-EBADMSG on XDR buffer overflow
+ *   %-EMSGSIZE if the decoded size of the body field exceeds 400 octets
+ */
+ssize_t xdr_stream_decode_opaque_auth(struct xdr_stream *xdr, u32 *flavor,
+				      void **body, unsigned int *body_len)
+{
+	ssize_t ret, len;
+
+	len = xdr_stream_decode_u32(xdr, flavor);
+	if (unlikely(len < 0))
+		return len;
+	ret = xdr_stream_decode_opaque_inline(xdr, body, RPC_MAX_AUTH_SIZE);
+	if (unlikely(ret < 0))
+		return ret;
+	*body_len = ret;
+	return len + ret;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_decode_opaque_auth);
+
+/**
+ * xdr_stream_encode_opaque_auth - Encode struct opaque_auth (RFC5531 S8.2)
+ * @xdr: pointer to xdr_stream
+ * @flavor: verifier flavor to encode
+ * @body: content of body to encode
+ * @body_len: length of body to encode
+ *
+ * Return values:
+ *   On success, returns length in bytes of XDR buffer consumed
+ *   %-EBADMSG on XDR buffer overflow
+ *   %-EMSGSIZE if the size of @body exceeds 400 octets
+ */
+ssize_t xdr_stream_encode_opaque_auth(struct xdr_stream *xdr, u32 flavor,
+				      void *body, unsigned int body_len)
+{
+	ssize_t ret, len;
+
+	if (unlikely(body_len > RPC_MAX_AUTH_SIZE))
+		return -EMSGSIZE;
+	len = xdr_stream_encode_u32(xdr, flavor);
+	if (unlikely(len < 0))
+		return len;
+	ret = xdr_stream_encode_opaque(xdr, body, body_len);
+	if (unlikely(ret < 0))
+		return ret;
+	return len + ret;
+}
+EXPORT_SYMBOL_GPL(xdr_stream_encode_opaque_auth);