Re: [PATCH v9 05/17] mm: mark vmas detached upon exit

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Fri, Jan 10, 2025 at 08:25:52PM -0800, Suren Baghdasaryan wrote:
> When exit_mmap() removes vmas belonging to an exiting task, it does not
> mark them as detached since they can't be reached by other tasks and they
> will be freed shortly. Once we introduce vma reuse, all vmas will have to
> be in detached state before they are freed to ensure vma when reused is
> in a consistent state. Add missing vma_mark_detached() before freeing the
> vma.

Hmm this really makes me worry that we'll see bugs from this detached
stuff, do we make this assumption anywhere else I wonder?

>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>

But regardless, prima facie, this looks fine, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

> ---
>  mm/vma.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vma.c b/mm/vma.c
> index b9cf552e120c..93ff42ac2002 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -413,10 +413,12 @@ void remove_vma(struct vm_area_struct *vma, bool unreachable)
>  	if (vma->vm_file)
>  		fput(vma->vm_file);
>  	mpol_put(vma_policy(vma));
> -	if (unreachable)
> +	if (unreachable) {
> +		vma_mark_detached(vma);
>  		__vm_area_free(vma);
> -	else
> +	} else {
>  		vm_area_free(vma);
> +	}
>  }
>
>  /*
> --
> 2.47.1.613.gc27f4b7a9f-goog
>