[PATCH 2/3] mm/vma: remove mmap_action->success_hook

[Lorenzo Stoakes]

This hook was introduced to work around code that seemed to absolutely
require access to a VMA pointer upon mmap().

However, providing this hook leaves a backdoor to drivers getting access to
the very thing mmap_prepare eliminates - a pointer to the VMA.

Let's solve this contradiction by removing it. The key intended user was
hugetlb, however it seems that the best course now is to avoid allowing all
drivers the ability to work around mmap_prepare, and find a different
solution there.

Signed-off-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>
---
 include/linux/mm_types.h        | 10 ----------
 mm/util.c                       |  2 --
 tools/testing/vma/include/dup.h | 10 ----------
 3 files changed, 22 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index a308e2c23b82..945c0a5386d6 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -843,16 +843,6 @@ struct mmap_action {
 	};
 	enum mmap_action_type type;
 
-	/*
-	 * If specified, this hook is invoked after the selected action has been
-	 * successfully completed. Note that the VMA write lock still held.
-	 *
-	 * The absolute minimum ought to be done here.
-	 *
-	 * Returns 0 on success, or an error code.
-	 */
-	int (*success_hook)(const struct vm_area_struct *vma);
-
 	/*
 	 * If specified, this hook is invoked when an error occurred when
 	 * attempting the selected action.
diff --git a/mm/util.c b/mm/util.c
index 3cc949a0b7ed..1555aa1487b8 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1396,8 +1396,6 @@ static int mmap_action_finish(struct vm_area_struct *vma,
 
 	if (!err)
 		err = call_vma_mapped(vma);
-	if (!err && action->success_hook)
-		err = action->success_hook(vma);
 
 	/* do_munmap() might take rmap lock, so release if held. */
 	maybe_rmap_unlock_action(vma, action);
diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index 9e0dfd3a85b0..bf67a80a8332 100644
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h
@@ -482,16 +482,6 @@ struct mmap_action {
 	};
 	enum mmap_action_type type;
 
-	/*
-	 * If specified, this hook is invoked after the selected action has been
-	 * successfully completed. Note that the VMA write lock still held.
-	 *
-	 * The absolute minimum ought to be done here.
-	 *
-	 * Returns 0 on success, or an error code.
-	 */
-	int (*success_hook)(const struct vm_area_struct *vma);
-
 	/*
 	 * If specified, this hook is invoked when an error occurred when
 	 * attempting the selection action.
-- 
2.54.0