Re: [PATCH v4 1/6] mm/gup: remove unused vmas parameter from get_user_pages()

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 18.04.23 um 17:49 schrieb Lorenzo Stoakes:
> No invocation of get_user_pages() uses the vmas parameter, so remove
> it.
>
> The GUP API is confusing and caveated. Recent changes have done much to
> improve that, however there is more we can do. Exporting vmas is a prime
> target as the caller has to be extremely careful to preclude their use
> after the mmap_lock has expired or otherwise be left with dangling
> pointers.
>
> Removing the vmas parameter focuses the GUP functions upon their primary
> purpose - pinning (and outputting) pages as well as performing the actions
> implied by the input flags.
>
> This is part of a patch series aiming to remove the vmas parameter
> altogether.

Astonishing that there are so few users of the original get_user_pages() 
API left.

> Suggested-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Acked-by: David Hildenbrand <david@xxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>

Acked-by: Christian König <christian.koenig@xxxxxxx> for the radeon parts.

Regards,
Christian.

> ---
>   arch/x86/kernel/cpu/sgx/ioctl.c     | 2 +-
>   drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
>   drivers/misc/sgi-gru/grufault.c     | 2 +-
>   include/linux/mm.h                  | 3 +--
>   mm/gup.c                            | 9 +++------
>   mm/gup_test.c                       | 5 ++---
>   virt/kvm/kvm_main.c                 | 2 +-
>   7 files changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 21ca0a831b70..5d390df21440 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -214,7 +214,7 @@ static int __sgx_encl_add_page(struct sgx_encl *encl,
>   	if (!(vma->vm_flags & VM_MAYEXEC))
>   		return -EACCES;
>   
> -	ret = get_user_pages(src, 1, 0, &src_page, NULL);
> +	ret = get_user_pages(src, 1, 0, &src_page);
>   	if (ret < 1)
>   		return -EFAULT;
>   
> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
> index 1e8e287e113c..0597540f0dde 100644
> --- a/drivers/gpu/drm/radeon/radeon_ttm.c
> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c
> @@ -362,7 +362,7 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_device *bdev, struct ttm_tt *ttm
>   		struct page **pages = ttm->pages + pinned;
>   
>   		r = get_user_pages(userptr, num_pages, write ? FOLL_WRITE : 0,
> -				   pages, NULL);
> +				   pages);
>   		if (r < 0)
>   			goto release_pages;
>   
> diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
> index b836936e9747..378cf02a2aa1 100644
> --- a/drivers/misc/sgi-gru/grufault.c
> +++ b/drivers/misc/sgi-gru/grufault.c
> @@ -185,7 +185,7 @@ static int non_atomic_pte_lookup(struct vm_area_struct *vma,
>   #else
>   	*pageshift = PAGE_SHIFT;
>   #endif
> -	if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page, NULL) <= 0)
> +	if (get_user_pages(vaddr, 1, write ? FOLL_WRITE : 0, &page) <= 0)
>   		return -EFAULT;
>   	*paddr = page_to_phys(page);
>   	put_page(page);
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 37554b08bb28..b14cc4972d0b 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2380,8 +2380,7 @@ long pin_user_pages_remote(struct mm_struct *mm,
>   			   unsigned int gup_flags, struct page **pages,
>   			   struct vm_area_struct **vmas, int *locked);
>   long get_user_pages(unsigned long start, unsigned long nr_pages,
> -			    unsigned int gup_flags, struct page **pages,
> -			    struct vm_area_struct **vmas);
> +		    unsigned int gup_flags, struct page **pages);
>   long pin_user_pages(unsigned long start, unsigned long nr_pages,
>   		    unsigned int gup_flags, struct page **pages,
>   		    struct vm_area_struct **vmas);
> diff --git a/mm/gup.c b/mm/gup.c
> index 1f72a717232b..7e454d6b157e 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2251,8 +2251,6 @@ long get_user_pages_remote(struct mm_struct *mm,
>    * @pages:      array that receives pointers to the pages pinned.
>    *              Should be at least nr_pages long. Or NULL, if caller
>    *              only intends to ensure the pages are faulted in.
> - * @vmas:       array of pointers to vmas corresponding to each page.
> - *              Or NULL if the caller does not require them.
>    *
>    * This is the same as get_user_pages_remote(), just with a less-flexible
>    * calling convention where we assume that the mm being operated on belongs to
> @@ -2260,16 +2258,15 @@ long get_user_pages_remote(struct mm_struct *mm,
>    * obviously don't pass FOLL_REMOTE in here.
>    */
>   long get_user_pages(unsigned long start, unsigned long nr_pages,
> -		unsigned int gup_flags, struct page **pages,
> -		struct vm_area_struct **vmas)
> +		    unsigned int gup_flags, struct page **pages)
>   {
>   	int locked = 1;
>   
> -	if (!is_valid_gup_args(pages, vmas, NULL, &gup_flags, FOLL_TOUCH))
> +	if (!is_valid_gup_args(pages, NULL, NULL, &gup_flags, FOLL_TOUCH))
>   		return -EINVAL;
>   
>   	return __get_user_pages_locked(current->mm, start, nr_pages, pages,
> -				       vmas, &locked, gup_flags);
> +				       NULL, &locked, gup_flags);
>   }
>   EXPORT_SYMBOL(get_user_pages);
>   
> diff --git a/mm/gup_test.c b/mm/gup_test.c
> index 8ae7307a1bb6..9ba8ea23f84e 100644
> --- a/mm/gup_test.c
> +++ b/mm/gup_test.c
> @@ -139,8 +139,7 @@ static int __gup_test_ioctl(unsigned int cmd,
>   						 pages + i);
>   			break;
>   		case GUP_BASIC_TEST:
> -			nr = get_user_pages(addr, nr, gup->gup_flags, pages + i,
> -					    NULL);
> +			nr = get_user_pages(addr, nr, gup->gup_flags, pages + i);
>   			break;
>   		case PIN_FAST_BENCHMARK:
>   			nr = pin_user_pages_fast(addr, nr, gup->gup_flags,
> @@ -161,7 +160,7 @@ static int __gup_test_ioctl(unsigned int cmd,
>   						    pages + i, NULL);
>   			else
>   				nr = get_user_pages(addr, nr, gup->gup_flags,
> -						    pages + i, NULL);
> +						    pages + i);
>   			break;
>   		default:
>   			ret = -EINVAL;
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index d255964ec331..7f31e0a4adb5 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2474,7 +2474,7 @@ static inline int check_user_page_hwpoison(unsigned long addr)
>   {
>   	int rc, flags = FOLL_HWPOISON | FOLL_WRITE;
>   
> -	rc = get_user_pages(addr, 1, flags, NULL, NULL);
> +	rc = get_user_pages(addr, 1, flags, NULL);
>   	return rc == -EHWPOISON;
>   }
>