On Sun, 27 Aug 2023 20:54:28 +0300
Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx> wrote:
> Use separate flag for tracking page count bumped by shmem->sgt to avoid
> imbalanced page counter during of drm_gem_shmem_free() time. It's fragile
> to assume that populated shmem->pages at a freeing time means that the
> count was bumped by drm_gem_shmem_get_pages_sgt(), using a flag removes
> the ambiguity.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 3 ++-
> drivers/gpu/drm/lima/lima_gem.c | 1 +
> include/drm/drm_gem_shmem_helper.h | 7 +++++++
> 3 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 78d9cf2355a5..db20b9123891 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -152,7 +152,7 @@ void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem)
> sg_free_table(shmem->sgt);
> kfree(shmem->sgt);
> }
> - if (shmem->pages)
> + if (shmem->got_sgt)
> drm_gem_shmem_put_pages(shmem);
Can't we just move this drm_gem_shmem_put_pages() call in the
if (shmem->sgt) block?
>
> drm_WARN_ON(obj->dev, shmem->pages_use_count);
> @@ -687,6 +687,7 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
> if (ret)
> goto err_free_sgt;
>
> + shmem->got_sgt = true;
> shmem->sgt = sgt;
>
> return sgt;
> diff --git a/drivers/gpu/drm/lima/lima_gem.c b/drivers/gpu/drm/lima/lima_gem.c
> index 4f9736e5f929..28602302c281 100644
> --- a/drivers/gpu/drm/lima/lima_gem.c
> +++ b/drivers/gpu/drm/lima/lima_gem.c
> @@ -89,6 +89,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
> }
>
> *bo->base.sgt = sgt;
> + bo->base.got_sgt = true;
>
> if (vm) {
> ret = lima_vm_map_bo(vm, bo, old_size >> PAGE_SHIFT);
> diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
> index ec70a98a8fe1..f87124629bb5 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -73,6 +73,13 @@ struct drm_gem_shmem_object {
> */
> unsigned int vmap_use_count;
>
> + /**
> + * @got_sgt:
> + *
> + * True if SG table was retrieved using drm_gem_shmem_get_pages_sgt()
> + */
> + bool got_sgt : 1;
> +
> /**
> * @imported_sgt:
> *
