Re: [PATCH v3 3/5] mm/mseal: small cleanups

[Jeff Xu <jeffxu@chromium.org>]

Hi Lorenzo,

On Wed, Jul 16, 2025 at 10:38 AM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> Drop the wholly unnecessary set_vma_sealed() helper(), which is used only
> once, and place VMA_ITERATOR() declarations in the correct place.
>
> Retain vma_is_sealed(), and use it instead of the confusingly named
> can_modify_vma(), so it's abundantly clear what's being tested, rather then
> a nebulous sense of 'can the VMA be modified'.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> Reviewed-by: Pedro Falcato <pfalcato@suse.de>
> Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Jeff Xu <jeffxu@chromium.org>

Thanks and regards
-Jeff
> ---
>  mm/madvise.c  |  2 +-
>  mm/mprotect.c |  2 +-
>  mm/mremap.c   |  2 +-
>  mm/mseal.c    |  9 +--------
>  mm/vma.c      |  4 ++--
>  mm/vma.h      | 20 ++------------------
>  6 files changed, 8 insertions(+), 31 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index dc3d8497b0f4..da6e0e7c00b5 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1286,7 +1286,7 @@ static bool can_madvise_modify(struct madvise_behavior *madv_behavior)
>         struct vm_area_struct *vma = madv_behavior->vma;
>
>         /* If the VMA isn't sealed we're good. */
> -       if (can_modify_vma(vma))
> +       if (!vma_is_sealed(vma))
>                 return true;
>
>         /* For a sealed VMA, we only care about discard operations. */
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 88709c01177b..807939177065 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -605,7 +605,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
>         unsigned long charged = 0;
>         int error;
>
> -       if (!can_modify_vma(vma))
> +       if (vma_is_sealed(vma))
>                 return -EPERM;
>
>         if (newflags == oldflags) {
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 5b7fe8f36074..8e93eca86721 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -1649,7 +1649,7 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
>                 return -EFAULT;
>
>         /* If mseal()'d, mremap() is prohibited. */
> -       if (!can_modify_vma(vma))
> +       if (vma_is_sealed(vma))
>                 return -EPERM;
>
>         /* Align to hugetlb page size, if required. */
> diff --git a/mm/mseal.c b/mm/mseal.c
> index 1308e88ab184..adbcc65e9660 100644
> --- a/mm/mseal.c
> +++ b/mm/mseal.c
> @@ -15,11 +15,6 @@
>  #include <linux/sched.h>
>  #include "internal.h"
>
> -static inline void set_vma_sealed(struct vm_area_struct *vma)
> -{
> -       vm_flags_set(vma, VM_SEALED);
> -}
> -
>  static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
>                 struct vm_area_struct **prev, unsigned long start,
>                 unsigned long end, vm_flags_t newflags)
> @@ -36,7 +31,7 @@ static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
>                 goto out;
>         }
>
> -       set_vma_sealed(vma);
> +       vm_flags_set(vma, VM_SEALED);
>  out:
>         *prev = vma;
>         return ret;
> @@ -53,7 +48,6 @@ static int check_mm_seal(unsigned long start, unsigned long end)
>  {
>         struct vm_area_struct *vma;
>         unsigned long nstart = start;
> -
>         VMA_ITERATOR(vmi, current->mm, start);
>
>         /* going through each vma to check. */
> @@ -78,7 +72,6 @@ static int apply_mm_seal(unsigned long start, unsigned long end)
>  {
>         unsigned long nstart;
>         struct vm_area_struct *vma, *prev;
> -
>         VMA_ITERATOR(vmi, current->mm, start);
>
>         vma = vma_iter_load(&vmi);
> diff --git a/mm/vma.c b/mm/vma.c
> index fc502b741dcf..75fd2759964b 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -1351,7 +1351,7 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
>                 }
>
>                 /* Don't bother splitting the VMA if we can't unmap it anyway */
> -               if (!can_modify_vma(vms->vma)) {
> +               if (vma_is_sealed(vms->vma)) {
>                         error = -EPERM;
>                         goto start_split_failed;
>                 }
> @@ -1371,7 +1371,7 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
>         for_each_vma_range(*(vms->vmi), next, vms->end) {
>                 long nrpages;
>
> -               if (!can_modify_vma(next)) {
> +               if (vma_is_sealed(next)) {
>                         error = -EPERM;
>                         goto modify_vma_failed;
>                 }
> diff --git a/mm/vma.h b/mm/vma.h
> index 85db5e880fcc..b123a9cdedb0 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -559,31 +559,15 @@ struct vm_area_struct *vma_iter_next_rewind(struct vma_iterator *vmi,
>  }
>
>  #ifdef CONFIG_64BIT
> -
>  static inline bool vma_is_sealed(struct vm_area_struct *vma)
>  {
>         return (vma->vm_flags & VM_SEALED);
>  }
> -
> -/*
> - * check if a vma is sealed for modification.
> - * return true, if modification is allowed.
> - */
> -static inline bool can_modify_vma(struct vm_area_struct *vma)
> -{
> -       if (unlikely(vma_is_sealed(vma)))
> -               return false;
> -
> -       return true;
> -}
> -
>  #else
> -
> -static inline bool can_modify_vma(struct vm_area_struct *vma)
> +static inline bool vma_is_sealed(struct vm_area_struct *vma)
>  {
> -       return true;
> +       return false;
>  }
> -
>  #endif
>
>  #if defined(CONFIG_STACK_GROWSUP)
> --
> 2.50.1
>