Re: [PATCH v3 3/8] mm: implement sticky VMA flags

[Lorenzo Stoakes]

On Mon, Nov 17, 2025 at 02:43:32PM -0800, Andrew Morton wrote:
> On Mon, 17 Nov 2025 20:02:03 +0000 Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> wrote:
>
> > Sorry to be a pain here, and can respin if it's easier, but can we update the
> > text of the comments below? As in discussion with Liam off-list we agreed that
> > the current wording is rather unclear and we can do a lot better.
> >
> > I provide the improved version inline below:
>
> np,
>
>  include/linux/mm.h               |    7 +++----
>  tools/testing/vma/vma_internal.h |    7 +++----
>  2 files changed, 6 insertions(+), 8 deletions(-)
>
> --- a/include/linux/mm.h~mm-implement-sticky-vma-flags-fix-2
> +++ a/include/linux/mm.h
> @@ -549,10 +549,9 @@ extern unsigned int kobjsize(const void
>   *                pressure on the memory system forcing the kernel to generate
>   *                new VMAs when old one could be extended instead.
>   *
> - *    VM_STICKY - If one VMA has flags which most be 'sticky', that is ones
> - *                which should propagate to all VMAs, but the other does not,
> - *                the merge should still proceed with the merge logic applying
> - *                sticky flags to the final VMA.
> + *    VM_STICKY - When merging VMAs, VMA flags must match, unless they are
> + *                'sticky'. If any sticky flags exist in either VMA, we simply
> + *                set all of them on the merged VMA.
>   */
>  #define VM_IGNORE_MERGE (VM_SOFTDIRTY | VM_STICKY)
>
> --- a/tools/testing/vma/vma_internal.h~mm-implement-sticky-vma-flags-fix-2
> +++ a/tools/testing/vma/vma_internal.h
> @@ -139,10 +139,9 @@ extern unsigned long dac_mmap_min_addr;
>   *                pressure on the memory system forcing the kernel to generate
>   *                new VMAs when old one could be extended instead.
>   *
> - *    VM_STICKY - If one VMA has flags which most be 'sticky', that is ones
> - *                which should propagate to all VMAs, but the other does not,
> - *                the merge should still proceed with the merge logic applying
> - *                sticky flags to the final VMA.
> + *    VM_STICKY - When merging VMAs, VMA flags must match, unless they are
> + *                'sticky'. If any sticky flags exist in either VMA, we simply
> + *                set all of them on the merged VMA.
>   */
>  #define VM_IGNORE_MERGE (VM_SOFTDIRTY | VM_STICKY)
>
> _
>

Thanks, much appreciated!

Despite your having very kindly done this, I apologise as I realise now after
all I have to respin... doh!

There was yet another typo as pointed out by Jane (and previously off-list,
Liam) plus Pedro (off-list) mentioned a silly mistake in my code fixup, and at
this point I think it'll keep us all a lot saner to just respin :>)

Cheers, Lorenzo