[Intel-gfx] [PATCH v3 3/3] drm/vgem: Keep a reference to the dmabuf when mmaped

[Chris Wilson]

In order to keep the dmabuf alive whilst the mmap is, we need to hold a
reference to the dmabuf and not the backing object. This is important as
the dmabuf not only keeps the object alive, but also the device so that

        dmabuf = vgem_create_dmabuf();
        ptr = mmap(... dmabuf ...);
        close(dmabuf);

persists across module-unload as well as device closure.

Testcase: igt/vgem_basic/unload
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Petri Latvala <petri.latv...@intel.com>
---
 drivers/gpu/drm/vgem/vgem_drv.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index f36c14729b55..74a83e41efa9 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -198,7 +198,6 @@ static struct drm_ioctl_desc vgem_ioctls[] = {
 
 static int vgem_mmap(struct file *filp, struct vm_area_struct *vma)
 {
-       unsigned long flags = vma->vm_flags;
        int ret;
 
        ret = drm_gem_mmap(filp, vma);
@@ -208,7 +207,7 @@ static int vgem_mmap(struct file *filp, struct 
vm_area_struct *vma)
        /* Keep the WC mmaping set by drm_gem_mmap() but our pages
         * are ordinary and not special.
         */
-       vma->vm_flags = flags | VM_DONTEXPAND | VM_DONTDUMP;
+       vma->vm_flags &= ~(VM_IO | VM_PFNMAP);
        return 0;
 }
 
@@ -281,21 +280,11 @@ static int vgem_prime_mmap(struct drm_gem_object *obj,
 {
        int ret;
 
-       if (obj->size < vma->vm_end - vma->vm_start)
-               return -EINVAL;
-
-       if (!obj->filp)
-               return -ENODEV;
-
-       ret = obj->filp->f_op->mmap(obj->filp, vma);
+       ret = drm_gem_mmap_obj(obj, obj->size, vma);
        if (ret)
                return ret;
 
-       fput(vma->vm_file);
-       vma->vm_file = get_file(obj->filp);
-       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
-       vma->vm_page_prot = 
pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
-
+       vma->vm_flags &= ~(VM_IO | VM_PFNMAP);
        return 0;
 }
 
-- 
2.9.3

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