From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755255AbcI0Nlg (ORCPT ); Tue, 27 Sep 2016 09:41:36 -0400 Received: from sender153-mail.zoho.com ([74.201.84.153]:25433 "EHLO sender153-mail.zoho.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754010AbcI0Nl2 (ORCPT ); Tue, 27 Sep 2016 09:41:28 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=zapps768; d=zoho.com; h=cc:from:subject:to:message-id:date:user-agent:mime-version:content-type; b=VQH+yj8gkxnQl8gnV9wv0lQFrw5R3iklZNII5ilq33qA1YgGGObWIYUhAyoXBn51FmFPeApE9F0U QnOYiFF5xszLptw84HC8rVj+2QX1CEBE0WOOpjZnMowOrSpj+DHr 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 Subject: [RFC PATCH v2 1/1] mm/vmalloc.c: correct a few logic error for __insert_vmap_area() To: Andrew Morton , Nicholas Piggin Message-ID: <57EA76F7.5090401@zoho.com> Date: Tue, 27 Sep 2016 21:41:11 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.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