Hi,
On Thu, Jun 16, 2016 at 03:50:31PM -0700, David Daney wrote:
> From: David Daney <david.daney@xxxxxxxxxx>
>
> When the core THP code is modifying the permissions of a huge page it
> calls pmd_modify(), which unfortunately was clearing the _PAGE_HUGE bit
> of the page table entry. The result can be kernel messages like:
>
> mm/memory.c:397: bad pmd 000000040080004d.
> mm/memory.c:397: bad pmd 00000003ff00004d.
> mm/memory.c:397: bad pmd 000000040100004d.
>
> or:
>
> ------------[ cut here ]------------
> WARNING: at mm/mmap.c:3200 exit_mmap+0x150/0x158()
> Modules linked in: ipv6 at24 octeon3_ethernet octeon_srio_nexus m25p80
> CPU: 12 PID: 1295 Comm: pmderr Not tainted 3.10.87-rt80-Cavium-Octeon #4
> Stack : 0000000040808000 0000000014009ce1 0000000000400004 ffffffff81076ba0
> 0000000000000000 0000000000000000 ffffffff85110000 0000000000000119
> 0000000000000004 0000000000000000 0000000000000119 43617669756d2d4f
> 0000000000000000 ffffffff850fda40 ffffffff85110000 0000000000000000
> 0000000000000000 0000000000000009 ffffffff809207a0 0000000000000c80
> ffffffff80f1bf20 0000000000000001 000000ffeca36828 0000000000000001
> 0000000000000000 0000000000000001 000000ffeca7e700 ffffffff80886924
> 80000003fd7a0000 80000003fd7a39b0 80000003fdea8000 ffffffff80885780
> 80000003fdea8000 ffffffff80f12218 000000000000000c 000000000000050f
> 0000000000000000 ffffffff80865c4c 0000000000000000 0000000000000000
> ...
> Call Trace:
> [<ffffffff80865c4c>] show_stack+0x6c/0xf8
> [<ffffffff80885780>] warn_slowpath_common+0x78/0xa8
> [<ffffffff809207a0>] exit_mmap+0x150/0x158
> [<ffffffff80882d44>] mmput+0x5c/0x110
> [<ffffffff8088b450>] do_exit+0x230/0xa68
> [<ffffffff8088be34>] do_group_exit+0x54/0x1d0
> [<ffffffff8088bfc0>] __wake_up_parent+0x0/0x18
>
> ---[ end trace c7b38293191c57dc ]---
> BUG: Bad rss-counter state mm:80000003fa168000 idx:1 val:1536
>
> Fix by not clearing _PAGE_HUGE bit.
>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Tested-by: Aaro Koskinen <aaro.koskinen@xxxxxxxxx>
A.
> ---
> arch/mips/include/asm/pgtable.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index a6b611f..477b1b1 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -632,7 +632,7 @@ static inline struct page *pmd_page(pmd_t pmd)
>
> static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
> {
> - pmd_val(pmd) = (pmd_val(pmd) & _PAGE_CHG_MASK) | pgprot_val(newprot);
> + pmd_val(pmd) = (pmd_val(pmd) & (_PAGE_CHG_MASK | _PAGE_HUGE)) | pgprot_val(newprot);
> return pmd;
> }
>
> --
> 1.7.11.7
>
>
