Re: [patch] mm, hugetlb: abort __get_user_pages if current has been oom killed

Kirill A. Shutemov
2015-03-09T04:31:09Z

On Sun, Mar 08, 2015 at 04:12:12PM -0700, David Rientjes wrote:
> If __get_user_pages() is faulting a significant number of hugetlb pages,
> usually as the result of mmap(MAP_LOCKED), it can potentially allocate a
> very large amount of memory.
>
> If the process has been oom killed, this will cause a lot of memory to
> be overcharged to its memcg since it has access to memory reserves or
> could potentially deplete all system memory reserves.
>
> In the same way that commit 4779280d1ea4 ("mm: make get_user_pages()
> interruptible") aborted for pending SIGKILLs when faulting non-hugetlb
> memory, based on the premise of commit 462e00cc7151 ("oom: stop
> allocating user memory if TIF_MEMDIE is set"), hugetlb page faults now
> terminate when the process has been oom killed.
>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
> mm/gup.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/gup.c b/mm/gup.c
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -457,6 +457,8 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> if (!vma || check_vma_flags(vma, gup_flags))
> return i ? : -EFAULT;
> if (is_vm_hugetlb_page(vma)) {
> + if (unlikely(fatal_signal_pending(current)))
> + return i ? : -ERESTARTSYS;
> i = follow_hugetlb_page(mm, vma, pages, vmas,
> &start, &nr_pages, i,
> gup_flags);

Shouldn't the check be inside loop in follow_hugetlb_page()?
IIUC, it wouldn't help much if nr_pages and hugetlb vma are big enough.

--
Kirill A. Shutemov