backport commit ("739f79fc9db1 mm: memcontrol: fix NULL pointer crash in test_clear_page_writeback()") to linux-4.9-stable

[Miles Chen <miles.chen@xxxxxxxxxxxx>]

Hi reviewers,

I suggest to backport commit "739f79fc9db1 mm: memcontrol: fix NULL
pointer crash in test_clear_page_writeback()" to linux-4.9 stable tree.

This email reports a NULL pointer crash in test_clear_page_writeback()
in android common kernel-4.9. There is a fix ("739f79fc9db1 mm:
memcontrol: fix NULL pointer crash in test_clear_page_writeback()") in
kernel-4.13.


commit: 739f79fc9db1b38f96b5a5109b247a650fbebf6d
subject: mm: memcontrol: fix NULL pointer crash in
test_clear_page_writeback()
kernel version to apply to: Linux-4.9

cheers,
Miles