Re: [PATCH v2 10/13] mm: make vm_area_desc utilise vma_flags_t only

Liam R. Howlett
2026-02-09T19:34:26Z

* Lorenzo Stoakes <lorenzo.stoakes@oracle.com> [260122 16:06]:
> Now we have eliminated all uses of vm_area_desc->vm_flags, eliminate this
> field, and have mmap_prepare users utilise the vma_flags_t
> vm_area_desc->vma_flags field only.
>
> As part of this change we alter is_shared_maywrite() to accept a
> vma_flags_t parameter, and introduce is_shared_maywrite_vm_flags() for use
> with legacy vm_flags_t flags.
>
> We also update struct mmap_state to add a union between vma_flags and
> vm_flags temporarily until the mmap logic is also converted to using
> vma_flags_t.
>
> Also update the VMA userland tests to reflect this change.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>

> ---
> include/linux/mm.h | 9 +++++++--
> include/linux/mm_types.h | 5 +----
> mm/filemap.c | 2 +-
> mm/util.c | 2 +-
> mm/vma.c | 11 +++++++----
> mm/vma.h | 3 +--
> tools/testing/vma/vma_internal.h | 9 +++++++--
> 7 files changed, 25 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e31f72a021ef..37e215de3343 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1290,15 +1290,20 @@ static inline bool vma_is_accessible(const struct vm_area_struct *vma)
> return vma->vm_flags & VM_ACCESS_FLAGS;
> }
>
> -static inline bool is_shared_maywrite(vm_flags_t vm_flags)
> +static inline bool is_shared_maywrite_vm_flags(vm_flags_t vm_flags)
> {
> return (vm_flags & (VM_SHARED | VM_MAYWRITE)) ==
> (VM_SHARED | VM_MAYWRITE);
> }
>
> +static inline bool is_shared_maywrite(const vma_flags_t *flags)
> +{
> + return vma_flags_test_all(flags, VMA_SHARED_BIT, VMA_MAYWRITE_BIT);
> +}
> +

Confusing git diff here, but looks okay.

> static inline bool vma_is_shared_maywrite(const struct vm_area_struct *vma)
> {
> - return is_shared_maywrite(vma->vm_flags);
> + return is_shared_maywrite(&vma->flags);
> }
>
> static inline
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index cdac328b46dc..6d98ff6bc2e5 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -887,10 +887,7 @@ struct vm_area_desc {
> /* Mutable fields. Populated with initial state. */
> pgoff_t pgoff;
> struct file *vm_file;
> - union {
> - vm_flags_t vm_flags;
> - vma_flags_t vma_flags;
> - };
> + vma_flags_t vma_flags;
> pgprot_t page_prot;
>
> /* Write-only fields. */
> diff --git a/mm/filemap.c b/mm/filemap.c
> index ebd75684cb0a..6cd7974d4ada 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -4012,7 +4012,7 @@ int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
>
> int generic_file_readonly_mmap_prepare(struct vm_area_desc *desc)
> {
> - if (is_shared_maywrite(desc->vm_flags))
> + if (is_shared_maywrite(&desc->vma_flags))
> return -EINVAL;
> return generic_file_mmap_prepare(desc);
> }
> diff --git a/mm/util.c b/mm/util.c
> index 97cae40c0209..b05ab6f97e11 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -1154,7 +1154,7 @@ int __compat_vma_mmap(const struct file_operations *f_op,
>
> .pgoff = vma->vm_pgoff,
> .vm_file = vma->vm_file,
> - .vm_flags = vma->vm_flags,
> + .vma_flags = vma->flags,
> .page_prot = vma->vm_page_prot,
>
> .action.type = MMAP_NOTHING, /* Default */
> diff --git a/mm/vma.c b/mm/vma.c
> index 39dcd9ddd4ba..be64f781a3aa 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -15,7 +15,10 @@ struct mmap_state {
> unsigned long end;
> pgoff_t pgoff;
> unsigned long pglen;
> - vm_flags_t vm_flags;
> + union {
> + vm_flags_t vm_flags;
> + vma_flags_t vma_flags;
> + };
> struct file *file;
> pgprot_t page_prot;
>
> @@ -2369,7 +2372,7 @@ static void set_desc_from_map(struct vm_area_desc *desc,
>
> desc->pgoff = map->pgoff;
> desc->vm_file = map->file;
> - desc->vm_flags = map->vm_flags;
> + desc->vma_flags = map->vma_flags;
> desc->page_prot = map->page_prot;
> }
>
> @@ -2650,7 +2653,7 @@ static int call_mmap_prepare(struct mmap_state *map,
> map->file_doesnt_need_get = true;
> map->file = desc->vm_file;
> }
> - map->vm_flags = desc->vm_flags;
> + map->vma_flags = desc->vma_flags;
> map->page_prot = desc->page_prot;
> /* User-defined fields. */
> map->vm_ops = desc->vm_ops;
> @@ -2823,7 +2826,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
> return -EINVAL;
>
> /* Map writable and ensure this isn't a sealed memfd. */
> - if (file && is_shared_maywrite(vm_flags)) {
> + if (file && is_shared_maywrite_vm_flags(vm_flags)) {
> int error = mapping_map_writable(file->f_mapping);
>
> if (error)
> diff --git a/mm/vma.h b/mm/vma.h
> index bb7fa5d2bde2..062672df8a65 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -286,8 +286,7 @@ static inline void set_vma_from_desc(struct vm_area_struct *vma,
> vma->vm_pgoff = desc->pgoff;
> if (desc->vm_file != vma->vm_file)
> vma_set_file(vma, desc->vm_file);
> - if (desc->vm_flags != vma->vm_flags)
> - vm_flags_set(vma, desc->vm_flags);
> + vma->flags = desc->vma_flags;
> vma->vm_page_prot = desc->page_prot;
>
> /* User-defined fields. */
> diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
> index 2b01794cbd61..2743f12ecf32 100644
> --- a/tools/testing/vma/vma_internal.h
> +++ b/tools/testing/vma/vma_internal.h
> @@ -1009,15 +1009,20 @@ static inline void vma_desc_clear_flags_mask(struct vm_area_desc *desc,
> #define vma_desc_clear_flags(desc, ...) \
> vma_desc_clear_flags_mask(desc, mk_vma_flags(__VA_ARGS__))
>
> -static inline bool is_shared_maywrite(vm_flags_t vm_flags)
> +static inline bool is_shared_maywrite_vm_flags(vm_flags_t vm_flags)
> {
> return (vm_flags & (VM_SHARED | VM_MAYWRITE)) ==
> (VM_SHARED | VM_MAYWRITE);
> }
>
> +static inline bool is_shared_maywrite(const vma_flags_t *flags)
> +{
> + return vma_flags_test_all(flags, VMA_SHARED_BIT, VMA_MAYWRITE_BIT);
> +}
> +
> static inline bool vma_is_shared_maywrite(struct vm_area_struct *vma)
> {
> - return is_shared_maywrite(vma->vm_flags);
> + return is_shared_maywrite(&vma->flags);
> }
>
> static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi)
> --
> 2.52.0
>