SUNRPC: Fix up xdr_set_page()

While we always want to align to the next page and/or the beginning of
the tail buffer when we call xdr_set_next_page(), the functions
xdr_align_data() and xdr_expand_hole() really want to align to the next
object in that next page or tail.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

net/sunrpc/xdr.c

@@ -1019,8 +1019,10 @@ static unsigned int xdr_set_page_base(struct xdr_stream *xdr,
 static void xdr_set_page(struct xdr_stream *xdr, unsigned int base,
 			 unsigned int len)
 {
-	if (xdr_set_page_base(xdr, base, len) == 0)
-		xdr_set_iov(xdr, xdr->buf->tail, 0, xdr_stream_remaining(xdr));
+	if (xdr_set_page_base(xdr, base, len) == 0) {
+		base -= xdr->buf->page_len;
+		xdr_set_iov(xdr, xdr->buf->tail, base, len);
+	}
 }
 
 static void xdr_set_next_page(struct xdr_stream *xdr)
@@ -1029,17 +1031,18 @@ 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;
-
-	xdr_set_page(xdr, newbase, PAGE_SIZE);
+	if (newbase < xdr->buf->page_len)
+		xdr_set_page_base(xdr, newbase, xdr_stream_remaining(xdr));
+	else
+		xdr_set_iov(xdr, xdr->buf->tail, 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) {
-		xdr_set_page(xdr, 0, PAGE_SIZE);
-	}
+	else if (xdr->iov == xdr->buf->head)
+		xdr_set_page(xdr, 0, xdr_stream_remaining(xdr));
 	return xdr->p != xdr->end;
 }
 
@@ -1277,7 +1280,7 @@ uint64_t xdr_align_data(struct xdr_stream *xdr, uint64_t offset, uint32_t length
 	}
 
 	xdr->nwords -= XDR_QUADLEN(length);
-	xdr_set_page(xdr, from + length, PAGE_SIZE);
+	xdr_set_page(xdr, from + length, xdr_stream_remaining(xdr));
 	return length;
 }
 EXPORT_SYMBOL_GPL(xdr_align_data);
@@ -1314,7 +1317,7 @@ uint64_t xdr_expand_hole(struct xdr_stream *xdr, uint64_t offset, uint64_t lengt
 	_zero_pages(buf->pages, buf->page_base + offset, length);
 
 	buf->len += length - (from - offset) - truncated;
-	xdr_set_page(xdr, offset + length, PAGE_SIZE);
+	xdr_set_page(xdr, offset + length, xdr_stream_remaining(xdr));
 	return length;
 }
 EXPORT_SYMBOL_GPL(xdr_expand_hole);