1 files changed, 121 insertions, 0 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 1052ccdb4e99..3feff529a764 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -19,6 +19,9 @@
 #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
  */
@@ -202,6 +205,88 @@ 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);
+
+	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);
+}
+
+static void
+_shift_data_left_tail(struct xdr_buf *buf, unsigned int pgto, size_t len)
+{
+	struct kvec *tail = buf->tail;
+
+	if (len > tail->iov_len)
+		len = tail->iov_len;
+
+	_copy_to_pages(buf->pages,
+		       buf->page_base + pgto,
+		       (char *)tail->iov_base,
+		       len);
+	tail->iov_len -= len;
+
+	if (tail->iov_len > 0)
+		memmove((char *)tail->iov_base,
+				tail->iov_base + len,
+				tail->iov_len);
+}
+
+/**
  * _shift_data_right_pages
  * @pages: vector of pages containing both the source and dest memory area.
  * @pgto_base: page vector address of destination
@@ -1128,6 +1213,42 @@ unsigned int xdr_read_pages(struct xdr_stream *xdr, unsigned int len)
 }
 EXPORT_SYMBOL_GPL(xdr_read_pages);
 
+uint64_t xdr_align_data(struct xdr_stream *xdr, uint64_t offset, uint32_t length)
+{
+	struct xdr_buf *buf = xdr->buf;
+	unsigned int from, bytes;
+	unsigned int shift = 0;
+
+	if ((offset + length) < offset ||
+	    (offset + length) > buf->page_len)
+		length = buf->page_len - offset;
+
+	xdr_realign_pages(xdr);
+	from = xdr_page_pos(xdr);
+	bytes = xdr->nwords << 2;
+	if (length < bytes)
+		bytes = length;
+
+	/* Move page data to the left */
+	if (from > offset) {
+		shift = min_t(unsigned int, bytes, buf->page_len - from);
+		_shift_data_left_pages(buf->pages,
+				       buf->page_base + offset,
+				       buf->page_base + from,
+				       shift);
+		bytes -= shift;
+
+		/* Move tail data into the pages, if necessary */
+		if (bytes > 0)
+			_shift_data_left_tail(buf, offset + shift, bytes);
+	}
+
+	xdr->nwords -= XDR_QUADLEN(length);
+	xdr_set_page(xdr, from + length, PAGE_SIZE);
+	return length;
+}
+EXPORT_SYMBOL_GPL(xdr_align_data);
+
 uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t length)
 {
 	struct xdr_buf *buf = xdr->buf;