[CIFS] Fix cifs update of page cache. Write at correct offset when out of memory

and add_to_page_cache fails.  

Thanks to Shaggy for pointing out the fix.

Signed-off-by: Steve French (sfrench@us.ibm.com)
Signed-off-by: Shaggy (shaggy@us.ibm.com)

fs/cifs/file.c

@@ -1352,6 +1352,8 @@ static void cifs_copy_cache_pages(struct address_space *mapping,
 				      GFP_KERNEL)) {
 			page_cache_release(page);
 			cFYI(1, ("Add page cache failed"));
+			data += PAGE_CACHE_SIZE;
+			bytes_read -= PAGE_CACHE_SIZE;
 			continue;
 		}