[RFC 5/5] vmalloc: vfree_exec: free unused vm_struct

[Song Liu <song@kernel.org>]

This is clearly not done yet, but it won't be too hard.

I would like to highlight that, we need both subtree_max_size and vm for
vmap_area in free_text tree. Therefore, we cannot keep the union in
vmam_area.
---
 include/linux/vmalloc.h | 12 ++----------
 mm/vmalloc.c            | 14 ++++++++++++--
 2 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 691c02ffe3db..de7731caadc0 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -68,16 +68,8 @@ struct vmap_area {
 	struct rb_node rb_node;         /* address sorted rbtree */
 	struct list_head list;          /* address sorted list */
 
-	/*
-	 * The following two variables can be packed, because
-	 * a vmap_area object can be either:
-	 *    1) in "free" tree (root is free_vmap_area_root)
-	 *    2) or "busy" tree (root is vmap_area_root)
-	 */
-	union {
-		unsigned long subtree_max_size; /* in "free" tree */
-		struct vm_struct *vm;           /* in "busy" tree */
-	};
+	unsigned long subtree_max_size;
+	struct vm_struct *vm;
 };
 
 /* archs that select HAVE_ARCH_HUGE_VMAP should override one or more of these */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5f3b5df9313f..57dd18882d37 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1428,6 +1428,7 @@ adjust_va_to_fit_type(struct rb_root *root, struct list_head *head,
 		 */
 		lva->va_start = va->va_start;
 		lva->va_end = nva_start_addr;
+		lva->vm = va->vm;
 
 		/*
 		 * Shrink this VA to remaining size.
@@ -3394,10 +3395,19 @@ void vfree_exec(const void *addr)
 	spin_unlock(&vmap_area_lock);
 
 	spin_lock(&free_text_area_lock);
-	merge_or_add_vmap_area_augment(va,
+	va = merge_or_add_vmap_area_augment(va,
 		&free_text_area_root, &free_text_area_list);
+	if (va) {
+		struct vm_struct *vm = va->vm;
+
+		if (vm != &text_tail_vm) {
+			va = __find_vmap_area((unsigned long)vm->addr,
+					      free_text_area_root.rb_node);
+			if (va->va_start == (unsigned long)vm->addr)
+				pr_info("%s TODO: free vm->addr %px\n", __func__, vm->addr);
+		}
+	}
 	spin_unlock(&free_text_area_lock);
-	/* TODO: when the whole vm_struct is not in use, free it */
 }
 
 /**
-- 
2.30.2