Re: [PATCH 3/5] mm: fix show_smap() for zone_device-pmd ranges

Andrew Morton
2016-09-06T20:16:06Z

On Tue, 06 Sep 2016 09:49:36 -0700 Dan Williams <dan.j.williams@intel.com> wrote:

> Attempting to dump /proc/<pid>/smaps for a process with pmd dax mappings
> currently results in the following VM_BUG_ONs:
>
> kernel BUG at mm/huge_memory.c:1105!
> task: ffff88045f16b140 task.stack: ffff88045be14000
> RIP: 0010:[<ffffffff81268f9b>] [<ffffffff81268f9b>] follow_trans_huge_pmd+0x2cb/0x340
> [..]
> Call Trace:
> [<ffffffff81306030>] smaps_pte_range+0xa0/0x4b0
> [<ffffffff814c2755>] ? vsnprintf+0x255/0x4c0
> [<ffffffff8123c46e>] __walk_page_range+0x1fe/0x4d0
> [<ffffffff8123c8a2>] walk_page_vma+0x62/0x80
> [<ffffffff81307656>] show_smap+0xa6/0x2b0
>
> kernel BUG at fs/proc/task_mmu.c:585!
> RIP: 0010:[<ffffffff81306469>] [<ffffffff81306469>] smaps_pte_range+0x499/0x4b0
> Call Trace:
> [<ffffffff814c2795>] ? vsnprintf+0x255/0x4c0
> [<ffffffff8123c46e>] __walk_page_range+0x1fe/0x4d0
> [<ffffffff8123c8a2>] walk_page_vma+0x62/0x80
> [<ffffffff81307696>] show_smap+0xa6/0x2b0
>
> These locations are sanity checking page flags that must be set for an
> anonymous transparent huge page, but are not set for the zone_device
> pages associated with dax mappings.

Acked-by: Andrew Morton <akpm@linux-foundation.org>