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SubjectRe: [PATCH 5/5] mm, memcontrol: use vma_is_anonymous() to check for anon VMA
On Mon, Jul 13, 2015 at 01:54:12PM +0300, Kirill A. Shutemov wrote:
> !vma->vm_file is not reliable to detect anon VMA, because not all
> drivers bother set it. Let's use vma_is_anonymous() instead.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@suse.cz>
> ---
> mm/memcontrol.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index acb93c554f6e..a624709f0dd7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4809,7 +4809,7 @@ static struct page *mc_handle_file_pte(struct vm_area_struct *vma,
> struct address_space *mapping;
> pgoff_t pgoff;
>
> - if (!vma->vm_file) /* anonymous vma */
> + if (vma_is_anonymous(vma)) /* anonymous vma */
> return NULL;
> if (!(mc.flags & MOVE_FILE))
> return NULL;

The next line does vma->vm_file->f_mapping, so it had better be !NULL.

It's not about reliably detecting anonymous vs. file, it is about
whether there is a mapping against which we can do find_get_page().


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