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 C9F5E6B0005 for ; Wed, 10 Aug 2016 01:33:17 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id o124so63798336pfg.1 for ; Tue, 09 Aug 2016 22:33:17 -0700 (PDT) Received: from sender153-mail.zoho.com (sender153-mail.zoho.com. [74.201.84.153]) by mx.google.com with ESMTPS id m18si46631988pfg.123.2016.08.09.22.33.16 for (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 09 Aug 2016 22:33:16 -0700 (PDT) Subject: Re: [PATCH] mm/vmalloc: fix align value calculation error References: <57A2F6A3.9080908@zoho.com> <57A2FE7B.5070505@zoho.com> <20160804142421.576426492d629f0839298f9a@linux-foundation.org> <20160809142832.623dfdbf666c08b8fc8772d2@linux-foundation.org> From: zijun_hu Message-ID: <57AABC8B.1040409@zoho.com> Date: Wed, 10 Aug 2016 13:32:59 +0800 MIME-Version: 1.0 In-Reply-To: <20160809142832.623dfdbf666c08b8fc8772d2@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: tj@kernel.org, hannes@cmpxchg.org, mhocko@kernel.org, minchan@kernel.org, zijun_hu@htc.com, rientjes@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org On 08/10/2016 05:28 AM, Andrew Morton wrote: > On Fri, 5 Aug 2016 23:48:21 +0800 zijun_hu wrote: > >> From: zijun_hu >> Date: Fri, 5 Aug 2016 22:10:07 +0800 >> Subject: [PATCH 1/1] mm/vmalloc: fix align value calculation error >> >> it causes double align requirement for __get_vm_area_node() if parameter >> size is power of 2 and VM_IOREMAP is set in parameter flags >> >> get_order_long() is implemented and used instead of fls_long() for >> fixing the bug > > Makes sense. I think. > >> --- a/include/linux/bitops.h >> +++ b/include/linux/bitops.h >> @@ -192,6 +192,23 @@ static inline unsigned fls_long(unsigned long l) >> } >> >> /** >> + * get_order_long - get order after rounding @l up to power of 2 >> + * @l: parameter >> + * >> + * it is same as get_count_order() but long type parameter >> + * or 0 is returned if @l == 0UL >> + */ >> +static inline int get_order_long(unsigned long l) >> +{ >> + if (l == 0UL) >> + return 0; >> + else if (l & (l - 1UL)) >> + return fls_long(l); >> + else >> + return fls_long(l) - 1; >> +} >> + >> +/** >> * __ffs64 - find first set bit in a 64 bit word >> * @word: The 64 bit word >> * >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index 91f44e7..7d717f3 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -1360,7 +1360,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size, >> >> BUG_ON(in_interrupt()); >> if (flags & VM_IOREMAP) >> - align = 1ul << clamp_t(int, fls_long(size), >> + align = 1ul << clamp_t(int, get_order_long(size), >> PAGE_SHIFT, IOREMAP_MAX_ORDER); >> >> size = PAGE_ALIGN(size); > > It would be better to call this get_count_order_long(), I think? To > match get_count_order()? > yes, i agree with you to correct function name i provide another patch called v2 based on your suggestion as shown below it have following correction against original patch v1 1) use name get_count_order_long() instead of get_order_long() 2) return -1 if @l == 0 to consist with get_order_long() 3) cast type to int before returning from get_count_order_long() 4) move up function parameter checking for __get_vm_area_node() 5) more commit message is offered to make issue and approach clear any comments about new patch is welcome this new patch called patch v2 is shown below