The iov_iter_get_pages_alloc function(introduced by 3.16 kernels, LU-6260) is a kernel function which does not use Lustre's hook to keep track of memory allocation and therefore the number of bytes tallied by Lustre's ll_free_user_pages() appeared to be 'extra'. This happens only to direct io read and it is not a real leak of memory. It can be reproduced by a number of sanity tests, such as 205, to result in the message similar to:

25243:0:(class_obd.c:646:cleanup_obdclass()) obd_memory max:
18446744073709549568, leaked: 18446744073709549568