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

[Kirill A. Shutemov]

On Tue, Sep 24, 2019 at 05:52:13PM -0700, Matthew Wilcox wrote:
> From: William Kucharski <william.kucharski@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> ---
>  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