Re: [PATCH 2/2] mm: Use vma_start_write_killable() in dup_mmap()

[Suren Baghdasaryan <surenb@google.com>]

On Mon, Nov 3, 2025 at 10:03 AM Matthew Wilcox (Oracle)
<willy@infradead.org> wrote:
>
> Allow waiting for the VMA write lock to be interrupted by fatal signals.
> We can remove the explicit check for fatal_signal_pending() as we will
> check it during vma_start_write_killable().  This is an improvement as
> we will not wait for the reader to finish before checking for signals.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Reviewed-by: Suren Baghdasaryan <surenb@google.com>

> ---
>  mm/mmap.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 5fd3b80fda1d..03773fe777b7 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1750,7 +1750,9 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
>         for_each_vma(vmi, mpnt) {
>                 struct file *file;
>
> -               vma_start_write(mpnt);
> +               retval = vma_start_write_killable(mpnt);
> +               if (retval < 0)
> +                       goto loop_out;
>                 if (mpnt->vm_flags & VM_DONTCOPY) {
>                         retval = vma_iter_clear_gfp(&vmi, mpnt->vm_start,
>                                                     mpnt->vm_end, GFP_KERNEL);
> @@ -1761,14 +1763,6 @@ __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
>                         continue;
>                 }
>                 charge = 0;
> -               /*
> -                * Don't duplicate many vmas if we've been oom-killed (for
> -                * example)
> -                */
> -               if (fatal_signal_pending(current)) {
> -                       retval = -EINTR;
> -                       goto loop_out;
> -               }
>                 if (mpnt->vm_flags & VM_ACCOUNT) {
>                         unsigned long len = vma_pages(mpnt);
>
> --
> 2.47.2
>