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

From: [email-masked] (Lorenzo Stoakes)
Date: Thu, 13 Oct 2016 01:20:15 +0100

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 <[email-masked]>
---
 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@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