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

From: Jarkko Sakkinen
Date: Sun Apr 23 2023 - 11:13:06 EST

On Tue Apr 18, 2023 at 6:49 PM EEST, Lorenzo Stoakes wrote:
> 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.
>
> 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>
> ---
> 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;
> }
>
> --
> 2.40.0


Acked-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>

BR, Jarkko