From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 5A0B66B026B for ; Tue, 27 Sep 2016 09:41:34 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id v67so29508927pfv.1 for ; Tue, 27 Sep 2016 06:41:34 -0700 (PDT) Received: from sender153-mail.zoho.com (sender153-mail.zoho.com. [74.201.84.153]) by mx.google.com with ESMTPS id ad9si2807779pad.196.2016.09.27.06.41.33 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 27 Sep 2016 06:41:33 -0700 (PDT) From: zijun_hu Subject: [RFC PATCH v2 1/1] mm/vmalloc.c: correct a few logic error for __insert_vmap_area() Message-ID: <57EA76F7.5090401@zoho.com> Date: Tue, 27 Sep 2016 21:41:11 +0800 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, zijun_hu@htc.com, torvalds@linux-foundation.org, tj@kernel.org, mingo@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, mgorman@techsingularity.net, npiggin@gmail.com, mhocko@kernel.org From: zijun_hu __insert_vmap_area() has a few obvious logic errors as shown by comments within below code segments static void __insert_vmap_area(struct vmap_area *va) { as a internal function parameter, we assume vmap_area @va has nonzero size ... if (va->va_start < tmp->va_end) p = &(*p)->rb_left; else if (va->va_end > tmp->va_start) p = &(*p)->rb_right; this else if condition is always true and meaningless due to va->va_end > va->va_start >= tmp_va->va_end > tmp_va->va_start normally else BUG(); this BUG() is meaningless too due to never be touched normally ... } the function don't implement the below desire behavior based on context if the vmap_area @va to be inserted is lower than that on the rbtree then we walk around the left branch of the given rbtree node; else if higher then right branch; else the former vmap_area has overlay with the latter then the existing BUG() is triggered it is fixed by correcting vmap_area rbtree walk manner as mentioned above BTW, we consider (va->va_end == tmp_va->va_start) as legal case since it indicate vmap_area @va neighbors with @tmp_va tightly Fixes: db64fe02258f ("mm: rewrite vmap layer") Signed-off-by: zijun_hu --- Hi npiggin, could you offer some comments for this patch since __insert_vmap_area() was introduced by you? thanks a lot Changes in v2: - more detailed commit message is provided mm/vmalloc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 91f44e78c516..cc6ecd60cc0e 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -321,10 +321,10 @@ static void __insert_vmap_area(struct vmap_area *va) parent = *p; tmp_va = rb_entry(parent, struct vmap_area, rb_node); - if (va->va_start < tmp_va->va_end) - p = &(*p)->rb_left; - else if (va->va_end > tmp_va->va_start) - p = &(*p)->rb_right; + if (va->va_end <= tmp_va->va_start) + p = &parent->rb_left; + else if (va->va_start >= tmp_va->va_end) + p = &parent->rb_right; else BUG(); } -- 1.9.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org