linux-kernel - [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink

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Date:   Mon, 27 May 2019 11:38:42 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Roman Gushchin <guro@...com>, Uladzislau Rezki <urezki@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink_va()

Move the BUG_ON()/RB_EMPTY_NODE() check under unlink_va()
function, it means if an empty node gets freed it is a BUG
thus is considered as faulty behaviour.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 mm/vmalloc.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 371aba9a4bf1..340959b81228 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -533,20 +533,16 @@ link_va(struct vmap_area *va, struct rb_root *root,
 static __always_inline void
 unlink_va(struct vmap_area *va, struct rb_root *root)
 {
-	/*
-	 * During merging a VA node can be empty, therefore
-	 * not linked with the tree nor list. Just check it.
-	 */
-	if (!RB_EMPTY_NODE(&va->rb_node)) {
-		if (root == &free_vmap_area_root)
-			rb_erase_augmented(&va->rb_node,
-				root, &free_vmap_area_rb_augment_cb);
-		else
-			rb_erase(&va->rb_node, root);
+	BUG_ON(RB_EMPTY_NODE(&va->rb_node));
 
-		list_del(&va->list);
-		RB_CLEAR_NODE(&va->rb_node);
-	}
+	if (root == &free_vmap_area_root)
+		rb_erase_augmented(&va->rb_node,
+			root, &free_vmap_area_rb_augment_cb);
+	else
+		rb_erase(&va->rb_node, root);
+
+	list_del(&va->list);
+	RB_CLEAR_NODE(&va->rb_node);
 }
 
 #if DEBUG_AUGMENT_PROPAGATE_CHECK
@@ -1187,8 +1183,6 @@ EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier);
 
 static void __free_vmap_area(struct vmap_area *va)
 {
-	BUG_ON(RB_EMPTY_NODE(&va->rb_node));
-
 	/*
 	 * Remove from the busy tree/list.
 	 */
-- 
2.11.0