diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index b144b1957dd9..f55c437124a2 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -696,6 +696,17 @@ int nfs_flush_incompatible(struct file *file, struct page *page)
 	return status;
 }
 
+/*
+ * If the page cache is marked as unsafe or invalid, then we can't rely on
+ * the PageUptodate() flag. In this case, we will need to turn off
+ * write optimisations that depend on the page contents being correct.
+ */
+static int nfs_write_pageuptodate(struct page *page, struct inode *inode)
+{
+	return PageUptodate(page) &&
+		!(NFS_I(inode)->cache_validity & (NFS_INO_REVAL_PAGECACHE|NFS_INO_INVALID_DATA));
+}
+
 /*
  * Update and possibly write a cached page of an NFS file.
  *
@@ -717,10 +728,13 @@ int nfs_updatepage(struct file *file, struct page *page,
 		(long long)(page_offset(page) +offset));
 
 	/* If we're not using byte range locks, and we know the page
-	 * is entirely in cache, it may be more efficient to avoid
-	 * fragmenting write requests.
+	 * is up to date, it may be more efficient to extend the write
+	 * to cover the entire page in order to avoid fragmentation
+	 * inefficiencies.
 	 */
-	if (PageUptodate(page) && inode->i_flock == NULL && !(file->f_mode & O_SYNC)) {
+	if (nfs_write_pageuptodate(page, inode) &&
+			inode->i_flock == NULL &&
+			!(file->f_mode & O_SYNC)) {
 		count = max(count + offset, nfs_page_length(page));
 		offset = 0;
 	}