From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id A66236B0623 for ; Thu, 8 Nov 2018 12:53:05 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id c8-v6so11309193edt.23 for ; Thu, 08 Nov 2018 09:53:05 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j5-v6si817565edk.25.2018.11.08.09.53.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Nov 2018 09:53:04 -0800 (PST) Date: Thu, 8 Nov 2018 18:53:01 +0100 From: Michal Hocko Subject: Re: [PATCH] mm: mmap: remove verify_mm_writelocked() Message-ID: <20181108175301.GC18390@dhcp22.suse.cz> References: <20181108174856.10811-1-tiny.windzz@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181108174856.10811-1-tiny.windzz@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Yangtao Li Cc: akpm@linux-foundation.org, rientjes@google.com, dan.j.williams@intel.com, linux@dominikbrodowski.net, dave.hansen@linux.intel.com, dwmw@amazon.co.uk, linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu 08-11-18 12:48:56, Yangtao Li wrote: > We should get rid of this function. It no longer serves its purpose.This > is a historical artifact from 2005 where do_brk was called outside of > the core mm.We do have a proper abstraction in vm_brk_flags and that one > does the locking properly.So there is no need to use this function. > > Signed-off-by: Yangtao Li Acked-by: Michal Hocko > --- > mm/mmap.c | 16 ---------------- > 1 file changed, 16 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index f7cd9cb966c0..1cee506494d2 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2910,16 +2910,6 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, > return ret; > } > > -static inline void verify_mm_writelocked(struct mm_struct *mm) > -{ > -#ifdef CONFIG_DEBUG_VM > - if (unlikely(down_read_trylock(&mm->mmap_sem))) { > - WARN_ON(1); > - up_read(&mm->mmap_sem); > - } > -#endif > -} > - > /* > * this is really a simplified "do_mmap". it only handles > * anonymous maps. eventually we may be able to do some > @@ -2946,12 +2936,6 @@ static int do_brk_flags(unsigned long addr, unsigned long len, unsigned long fla > if (error) > return error; > > - /* > - * mm->mmap_sem is required to protect against another thread > - * changing the mappings in case we sleep. > - */ > - verify_mm_writelocked(mm); > - > /* > * Clear old maps. this also does some error checking for us > */ > -- > 2.17.0 > -- Michal Hocko SUSE Labs