Re: [PATCH 14/15] mm: Align THP mappings for non-DAX

Kirill A. Shutemov
2019-10-01T10:46:01Z

On Tue, Sep 24, 2019 at 05:52:13PM -0700, Matthew Wilcox wrote:
> From: William Kucharski <william.kucharski@oracle.com>
>
> When we have the opportunity to use transparent huge pages to map a
> file, we want to follow the same rules as DAX.
>
> Signed-off-by: William Kucharski <william.kucharski@oracle.com>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> mm/huge_memory.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index cbe7d0619439..670a1780bd2f 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -563,8 +563,6 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
>
> if (addr)
> goto out;
> - if (!IS_DAX(filp->f_mapping->host) || !IS_ENABLED(CONFIG_FS_DAX_PMD))
> - goto out;
>
> addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE);
> if (addr)

I think you reducing ASLR without any real indication that THP is relevant
for the VMA. We need to know if any huge page allocation will be
*attempted* for the VMA or the file.

--
Kirill A. Shutemov