Hi Nirmoy,
On Wed, Mar 15, 2023 at 11:54:46AM +0100, Nirmoy Das wrote:
> Add a comment why there is a obj refcount inc before installing
> the vm_ops for the mmap call. Also remove the invalid older comment
> as drm API(drm_gem_prime_mmap()) will hold an obj reference before
> calling this driver mmap callback so we can't have 0-refcnted
> object here.
>
> Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> Signed-off-by: Nirmoy Das <nirmoy.das@xxxxxxxxx>
fine with me!
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
Andi
> ---
> drivers/gpu/drm/i915/gem/i915_gem_mman.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> index d3c1dee16af2..0bc8c3818443 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> @@ -952,9 +952,10 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
> vma_pages(vma));
> if (node && drm_vma_node_is_allowed(node, priv)) {
> /*
> - * Skip 0-refcnted objects as it is in the process of being
> - * destroyed and will be invalid when the vma manager lock
> - * is released.
> + * When we install vm_ops for mmap we are too late for
> + * the vm_ops->open() which increases the ref_count of
> + * this obj and then it gets decreased by the vm_ops->close().
> + * To balance this increase the obj ref_count here.
> */
> if (!node->driver_private) {
> mmo = container_of(node, struct i915_mmap_offset, vma_node);
> --
> 2.39.0
