mm: fix get_user_pages() vs device-dax pud mappings
A new unit test for the device-dax 1GB enabling currently fails with this warning before hanging the test thread: WARNING: CPU: 0 PID: 21 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0 percpu ref (dax_pmem_percpu_release [dax_pmem]) <= 0 (0) after switching to atomic [..] CPU: 0 PID: 21 Comm: rcuos/1 Tainted: G O 4.10.0-rc7-next-20170207+ #944 [..] Call Trace: dump_stack+0x86/0xc3 __warn+0xcb/0xf0 warn_slowpath_fmt+0x5f/0x80 ? rcu_nocb_kthread+0x27a/0x510 ? dax_pmem_percpu_exit+0x50/0x50 [dax_pmem] percpu_ref_switch_to_atomic_rcu+0x1e3/0x1f0 ? percpu_ref_exit+0x60/0x60 rcu_nocb_kthread+0x339/0x510 ? rcu_nocb_kthread+0x27a/0x510 kthread+0x101/0x140 The get_user_pages() path needs to arrange for references to be taken against the dev_pagemap instance backing the pud mapping. Refactor the existing __gup_device_huge_pmd() to also account for the pud case. Link: http://lkml.kernel.org/r/148653181153.38226.9605457830505509385.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: NDan Williams <dan.j.williams@intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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