Re: [PATCH v4] mm: Add MREMAP_DONTUNMAP to mremap().

Kirill A. Shutemov
2020-02-13T12:07:57Z

On Mon, Feb 10, 2020 at 06:12:39AM -0800, Brian Geffon wrote:
> Hi Kirill,
> If the old_len == new_len then there is no change in the number of
> locked pages they just moved, if the new_len < old_len then the
> process of unmapping (new_len - old_len) bytes from the old mapping
> will handle the locked page accounting. So in this special case where
> we're growing the VMA, vma_to_resize() will enforce that growing the
> vma doesn't exceed RLIMIT_MEMLOCK, but vma_to_resize() doesn't handle
> incrementing mm->locked_bytes which is why we have that special case
> incrementing it here.

But if you do the operation for the VM_LOCKED vma, you'll have two locked
VMA's now, right? Where do you account the old locked vma you left behind?

--
Kirill A. Shutemov