Re: [PATCH V4 1/6] mm: mlock: Refactor mlock, munlock, and munlockall code

Kirill A. Shutemov
2015-07-22T10:42:32Z

On Tue, Jul 21, 2015 at 03:59:36PM -0400, Eric B Munson wrote:
> @@ -648,20 +656,23 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
> start &= PAGE_MASK;
>
> down_write(&current->mm->mmap_sem);
> - ret = do_mlock(start, len, 0);
> + ret = apply_vma_flags(start, len, flags, false);
> up_write(&current->mm->mmap_sem);
>
> return ret;
> }
>
> +SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
> +{
> + return do_munlock(start, len, VM_LOCKED);
> +}
> +
> static int do_mlockall(int flags)
> {
> struct vm_area_struct * vma, * prev = NULL;
>
> if (flags & MCL_FUTURE)
> current->mm->def_flags |= VM_LOCKED;
> - else
> - current->mm->def_flags &= ~VM_LOCKED;

I think this is wrong.

With current code mlockall(MCL_CURRENT) after mlockall(MCL_FUTURE |
MCL_CURRENT) would undo future mlocking, without unlocking currently
mlocked memory.

The change will break the use-case.

> if (flags == MCL_FUTURE)
> goto out;
>

--
Kirill A. Shutemov