Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932562Ab3ICHmK (ORCPT ); Tue, 3 Sep 2013 03:42:10 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:31016 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S932502Ab3ICHmI (ORCPT ); Tue, 3 Sep 2013 03:42:08 -0400 X-IronPort-AV: E=Sophos;i="4.89,1012,1367942400"; d="scan'208";a="8389016" Message-ID: <522592BF.1090102@cn.fujitsu.com> Date: Tue, 03 Sep 2013 15:41:51 +0800 From: Zhang Yanfei User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Wanpeng Li CC: Andrew Morton , Joonsoo Kim , David Rientjes , KOSAKI Motohiro , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 4/4] mm/vmalloc: don't assume vmap_area w/o VM_VM_AREA flag is vm_map_ram allocation References: <1378191706-29696-1-git-send-email-liwanp@linux.vnet.ibm.com> <1378191706-29696-4-git-send-email-liwanp@linux.vnet.ibm.com> In-Reply-To: <1378191706-29696-4-git-send-email-liwanp@linux.vnet.ibm.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/09/03 15:40:00, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2013/09/03 15:40:00, Serialize complete at 2013/09/03 15:40:00 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2229 Lines: 73 On 09/03/2013 03:01 PM, Wanpeng Li wrote: > There is a race window between vmap_area free and show vmap_area information. > > A B > > remove_vm_area > spin_lock(&vmap_area_lock); > va->flags &= ~VM_VM_AREA; Here we also do: va->vm = NULL; And see below.... > spin_unlock(&vmap_area_lock); > spin_lock(&vmap_area_lock); > if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEZING)) > return 0; > if (!(va->flags & VM_VM_AREA)) { > seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", > (void *)va->va_start, (void *)va->va_end, > va->va_end - va->va_start); > return 0; > } > free_unmap_vmap_area(va); > flush_cache_vunmap > free_unmap_vmap_area_noflush > unmap_vmap_area > free_vmap_area_noflush > va->flags |= VM_LAZY_FREE > > The assumption is introduced by commit: d4033afd(mm, vmalloc: iterate vmap_area_list, > instead of vmlist, in vmallocinfo()). This patch fix it by drop the assumption and > keep not dump vm_map_ram allocation information as the logic before that commit. > > Signed-off-by: Wanpeng Li > --- > mm/vmalloc.c | 7 ------- > 1 file changed, 7 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 5368b17..62b7932 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2586,13 +2586,6 @@ static int s_show(struct seq_file *m, void *p) > if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEING)) > return 0; > > - if (!(va->flags & VM_VM_AREA)) { > - seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", > - (void *)va->va_start, (void *)va->va_end, > - va->va_end - va->va_start); > - return 0; > - } > - > v = va->vm; If we remove the if test above, in the window you said above, va->vm is NULL, but below we will still try to access the members of this vm_struct, which will cause problems... Correct me if I am wrong, please. > > seq_printf(m, "0x%pK-0x%pK %7ld", > -- Thanks. Zhang Yanfei -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/