Re: [PATCH 05/10] mm: replace get_vaddr_frames() write/force parameters with gup_flags

Jan Kara
2016-10-19T07:34:35Z

On Thu 13-10-16 01:20:15, Lorenzo Stoakes wrote:
> This patch removes the write and force parameters from get_vaddr_frames() and
> replaces them with a gup_flags parameter to make the use of FOLL_FORCE explicit
> in callers as use of this flag can result in surprising behaviour (and hence
> bugs) within the mm subsystem.
>
> Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>

Looks good. You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> drivers/gpu/drm/exynos/exynos_drm_g2d.c | 3 ++-
> drivers/media/platform/omap/omap_vout.c | 2 +-
> drivers/media/v4l2-core/videobuf2-memops.c | 6 +++++-
> include/linux/mm.h | 2 +-
> mm/frame_vector.c | 13 ++-----------
> 5 files changed, 11 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_g2d.c b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> index aa92dec..fbd13fa 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_g2d.c
> @@ -488,7 +488,8 @@ static dma_addr_t *g2d_userptr_get_dma_addr(struct drm_device *drm_dev,
> goto err_free;
> }
>
> - ret = get_vaddr_frames(start, npages, true, true, g2d_userptr->vec);
> + ret = get_vaddr_frames(start, npages, FOLL_FORCE | FOLL_WRITE,
> + g2d_userptr->vec);
> if (ret != npages) {
> DRM_ERROR("failed to get user pages from userptr.\n");
> if (ret < 0)
> diff --git a/drivers/media/platform/omap/omap_vout.c b/drivers/media/platform/omap/omap_vout.c
> index e668dde..a31b95c 100644
> --- a/drivers/media/platform/omap/omap_vout.c
> +++ b/drivers/media/platform/omap/omap_vout.c
> @@ -214,7 +214,7 @@ static int omap_vout_get_userptr(struct videobuf_buffer *vb, u32 virtp,
> if (!vec)
> return -ENOMEM;
>
> - ret = get_vaddr_frames(virtp, 1, true, false, vec);
> + ret = get_vaddr_frames(virtp, 1, FOLL_WRITE, vec);
> if (ret != 1) {
> frame_vector_destroy(vec);
> return -EINVAL;
> diff --git a/drivers/media/v4l2-core/videobuf2-memops.c b/drivers/media/v4l2-core/videobuf2-memops.c
> index 3c3b517..1cd322e 100644
> --- a/drivers/media/v4l2-core/videobuf2-memops.c
> +++ b/drivers/media/v4l2-core/videobuf2-memops.c
> @@ -42,6 +42,10 @@ struct frame_vector *vb2_create_framevec(unsigned long start,
> unsigned long first, last;
> unsigned long nr;
> struct frame_vector *vec;
> + unsigned int flags = FOLL_FORCE;
> +
> + if (write)
> + flags |= FOLL_WRITE;
>
> first = start >> PAGE_SHIFT;
> last = (start + length - 1) >> PAGE_SHIFT;
> @@ -49,7 +53,7 @@ struct frame_vector *vb2_create_framevec(unsigned long start,
> vec = frame_vector_create(nr);
> if (!vec)
> return ERR_PTR(-ENOMEM);
> - ret = get_vaddr_frames(start & PAGE_MASK, nr, write, true, vec);
> + ret = get_vaddr_frames(start & PAGE_MASK, nr, flags, vec);
> if (ret < 0)
> goto out_destroy;
> /* We accept only complete set of PFNs */
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 27ab538..5ff084f6 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1305,7 +1305,7 @@ struct frame_vector {
> struct frame_vector *frame_vector_create(unsigned int nr_frames);
> void frame_vector_destroy(struct frame_vector *vec);
> int get_vaddr_frames(unsigned long start, unsigned int nr_pfns,
> - bool write, bool force, struct frame_vector *vec);
> + unsigned int gup_flags, struct frame_vector *vec);
> void put_vaddr_frames(struct frame_vector *vec);
> int frame_vector_to_pages(struct frame_vector *vec);
> void frame_vector_to_pfns(struct frame_vector *vec);
> diff --git a/mm/frame_vector.c b/mm/frame_vector.c
> index 81b6749..db77dcb 100644
> --- a/mm/frame_vector.c
> +++ b/mm/frame_vector.c
> @@ -11,10 +11,7 @@
> * get_vaddr_frames() - map virtual addresses to pfns
> * @start: starting user address
> * @nr_frames: number of pages / pfns from start to map
> - * @write: whether pages will be written to by the caller
> - * @force: whether to force write access even if user mapping is
> - * readonly. See description of the same argument of
> - get_user_pages().
> + * @gup_flags: flags modifying lookup behaviour
> * @vec: structure which receives pages / pfns of the addresses mapped.
> * It should have space for at least nr_frames entries.
> *
> @@ -34,23 +31,17 @@
> * This function takes care of grabbing mmap_sem as necessary.
> */
> int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
> - bool write, bool force, struct frame_vector *vec)
> + unsigned int gup_flags, struct frame_vector *vec)
> {
> struct mm_struct *mm = current->mm;
> struct vm_area_struct *vma;
> int ret = 0;
> int err;
> int locked;
> - unsigned int gup_flags = 0;
>
> if (nr_frames == 0)
> return 0;
>
> - if (write)
> - gup_flags |= FOLL_WRITE;
> - if (force)
> - gup_flags |= FOLL_FORCE;
> -
> if (WARN_ON_ONCE(nr_frames > vec->nr_allocated))
> nr_frames = vec->nr_allocated;
>
> --
> 2.10.0
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
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