Re: [PATCH RESEND v3 05/10] mm/vma: de-duplicate __vma_enter_locked() error path

[Suren Baghdasaryan <surenb@google.com>]

On Thu, Jan 22, 2026 at 5:02 AM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> We're doing precisely the same thing that __vma_exit_locked() does, so
> de-duplicate this code and keep the refcount primitive in one place.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

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

> ---
>  mm/mmap_lock.c | 21 ++++++++++++---------
>  1 file changed, 12 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
> index 9563bfb051f4..7a0361cff6db 100644
> --- a/mm/mmap_lock.c
> +++ b/mm/mmap_lock.c
> @@ -45,6 +45,14 @@ EXPORT_SYMBOL(__mmap_lock_do_trace_released);
>
>  #ifdef CONFIG_MMU
>  #ifdef CONFIG_PER_VMA_LOCK
> +
> +static inline void __vma_exit_locked(struct vm_area_struct *vma, bool *detached)
> +{
> +       *detached = refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG,
> +                                         &vma->vm_refcnt);
> +       __vma_lockdep_release_exclusive(vma);
> +}
> +
>  /*
>   * __vma_enter_locked() returns 0 immediately if the vma is not
>   * attached, otherwise it waits for any current readers to finish and
> @@ -77,7 +85,10 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
>                    refcount_read(&vma->vm_refcnt) == tgt_refcnt,
>                    state);
>         if (err) {
> -               if (refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG, &vma->vm_refcnt)) {
> +               bool detached;
> +
> +               __vma_exit_locked(vma, &detached);
> +               if (detached) {
>                         /*
>                          * The wait failed, but the last reader went away
>                          * as well.  Tell the caller the VMA is detached.
> @@ -85,7 +96,6 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
>                         WARN_ON_ONCE(!detaching);
>                         err = 0;
>                 }
> -               __vma_lockdep_release_exclusive(vma);
>                 return err;
>         }
>         __vma_lockdep_stat_mark_acquired(vma);
> @@ -93,13 +103,6 @@ static inline int __vma_enter_locked(struct vm_area_struct *vma,
>         return 1;
>  }
>
> -static inline void __vma_exit_locked(struct vm_area_struct *vma, bool *detached)
> -{
> -       *detached = refcount_sub_and_test(VM_REFCNT_EXCLUDE_READERS_FLAG,
> -                                         &vma->vm_refcnt);
> -       __vma_lockdep_release_exclusive(vma);
> -}
> -
>  int __vma_start_write(struct vm_area_struct *vma, unsigned int mm_lock_seq,
>                 int state)
>  {
> --
> 2.52.0