[PATCH v2 01/25] mm: Add kfd_process pointer to mm_struct

[Oded Gabbay <oded.gabbay@amd.com>]

Forgot to add mm mailing list. Sorry.

This patch enables the amdkfd driver to retrieve the kfd_process
object from the process's mm_struct. This is needed because kfd_process
lifespan is bound to the process's mm_struct lifespan.

When amdkfd is notified about an mm_struct tear-down, it checks if the
kfd_process pointer is valid. If so, it releases the kfd_process object
and all relevant resources.

In v3 of the patchset I will update the binding to match the final discussions
on [PATCH 1/8] mmput: use notifier chain to call subsystem exit handler.
In the meantime, I'm going to try and see if I can drop the kfd_process
in mm_struct and remove the use of the new notification chain in mmput.
Instead, I will try to use the mmu release notifier.

Signed-off-by: Oded Gabbay <oded.gabbay@amd.com>
---
  include/linux/mm_types.h | 14 ++++++++++++++
  1 file changed, 14 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 678097c..ff71496 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -20,6 +20,10 @@
  struct hmm;
  #endif
  +#if defined(CONFIG_HSA_RADEON) || defined(CONFIG_HSA_RADEON_MODULE)
+struct kfd_process;
+#endif
+
  #ifndef AT_VECTOR_SIZE_ARCH
  #define AT_VECTOR_SIZE_ARCH 0
  #endif
@@ -439,6 +443,16 @@ struct mm_struct {
  	 */
  	struct hmm *hmm;
  #endif
+#if defined(CONFIG_HSA_RADEON) || defined(CONFIG_HSA_RADEON_MODULE)
+	/*
+	 * kfd always register an mmu_notifier we rely on mmu notifier to keep
+	 * refcount on mm struct as well as forbiding registering kfd on a
+	 * dying mm
+	 *
+	 * This field is set with mmap_sem old in write mode.
+	 */
+	struct kfd_process *kfd_process;
+#endif
  #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
  	pgtable_t pmd_huge_pte; /* protected by page_table_lock */
  #endif
-- 
1.9.1