* Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> [250509 08:14]:
> Secretmem has a simple .mmap() hook which is easily converted to the new
> .mmap_prepare() callback.
>
> Importantly, it's a rare instance of an driver that manipulates a VMA which
> is mergeable (that is, not a VM_SPECIAL mapping) while also adjusting VMA
> flags which may adjust mergeability, meaning the retry merge logic might
> impact whether or not the VMA is merged.
>
> By using .mmap_prepare() there's no longer any need to retry the merge
> later as we can simply set the correct flags from the start.
>
> This change therefore allows us to remove the retry merge logic in a
> subsequent commit.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> Acked-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> ---
> mm/secretmem.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 1b0a214ee558..589b26c2d553 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -120,18 +120,18 @@ static int secretmem_release(struct inode *inode, struct file *file)
> return 0;
> }
>
> -static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
> +static int secretmem_mmap_prepare(struct vm_area_desc *desc)
> {
> - unsigned long len = vma->vm_end - vma->vm_start;
> + const unsigned long len = desc->end - desc->start;
>
> - if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
> + if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
> return -EINVAL;
>
> - if (!mlock_future_ok(vma->vm_mm, vma->vm_flags | VM_LOCKED, len))
> + if (!mlock_future_ok(desc->mm, desc->vm_flags | VM_LOCKED, len))
> return -EAGAIN;
>
> - vm_flags_set(vma, VM_LOCKED | VM_DONTDUMP);
> - vma->vm_ops = &secretmem_vm_ops;
> + desc->vm_flags |= VM_LOCKED | VM_DONTDUMP;
> + desc->vm_ops = &secretmem_vm_ops;
>
> return 0;
> }
> @@ -143,7 +143,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma)
>
> static const struct file_operations secretmem_fops = {
> .release = secretmem_release,
> - .mmap = secretmem_mmap,
> + .mmap_prepare = secretmem_mmap_prepare,
> };
>
> static int secretmem_migrate_folio(struct address_space *mapping,
> --
> 2.49.0
>
