Re: [PATCH v3 1/3] mm/vma: cleanup error handling path in vma_expand()

[Suren Baghdasaryan <surenb@google.com>]

On Mon, Mar 2, 2026 at 5:57 AM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> On Wed, Feb 25, 2026 at 11:06:07PM -0800, Suren Baghdasaryan wrote:
> > vma_expand() error handling is a bit confusing with "if (ret) return ret;"
> > mixed with "if (!ret && ...) ret = ...;". Simplify the code to check
> > for errors and return immediately after an operation that might fail.
> > This also makes later changes to this function more readable.
> >
> > No functional change intended.
> >
> > Suggested-by: Jann Horn <jannh@google.com>
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>
> LGTM, so:
>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Thanks!

>
> > ---
> >  mm/vma.c | 12 ++++++++----
> >  1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/vma.c b/mm/vma.c
> > index be64f781a3aa..bb4d0326fecb 100644
> > --- a/mm/vma.c
> > +++ b/mm/vma.c
> > @@ -1186,12 +1186,16 @@ int vma_expand(struct vma_merge_struct *vmg)
> >        * Note that, by convention, callers ignore OOM for this case, so
> >        * we don't need to account for vmg->give_up_on_mm here.
> >        */
> > -     if (remove_next)
> > +     if (remove_next) {
> >               ret = dup_anon_vma(target, next, &anon_dup);
> > -     if (!ret && vmg->copied_from)
> > +             if (ret)
> > +                     return ret;
> > +     }
>
> > +     if (vmg->copied_from) {
> >               ret = dup_anon_vma(target, vmg->copied_from, &anon_dup);
> > -     if (ret)
> > -             return ret;
> > +             if (ret)
> > +                     return ret;
> > +     }
>
> Thanks that is an improvement!
>
> I was going to suggest declaring 'ret' in each block but that kinda adds noise
> so this is fine.
>
> Maybe rename 'ret' to 'err' but not a big deal, this function could do with a
> little more cleanup too I think!

Sure, since I'll be posting a new version I'll do the rename too.
Cheers!

>
> >
> >       if (remove_next) {
> >               vma_start_write(next);
> > --
> > 2.53.0.414.gf7e9f6c205-goog
> >
>