drm/amdkfd: Don't dereference kfd_process.mm

The kfd_process doesn't own a reference to the mm_struct, so it can
disappear without warning even while the kfd_process still exists.

Therefore, avoid dereferencing the kfd_process.mm pointer and make
it opaque. Use get_task_mm to get a temporary reference to the mm
when it's needed.

v2: removed unnecessary WARN_ON

Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index 7d86ec9790d3..1a483a7ecd4e 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -494,7 +494,12 @@ struct kfd_process {
 	 */
 	struct hlist_node kfd_processes;
 
-	struct mm_struct *mm;
+	/*
+	 * Opaque pointer to mm_struct. We don't hold a reference to
+	 * it so it should never be dereferenced from here. This is
+	 * only used for looking up processes by their mm.
+	 */
+	void *mm;
 
 	struct mutex mutex;