From patchwork Tue Apr 21 14:50:31 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kinglong Mee X-Patchwork-Id: 6249491 Return-Path: X-Original-To: patchwork-linux-nfs@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 9E8839F313 for ; Tue, 21 Apr 2015 14:50:47 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id C369C202FE for ; Tue, 21 Apr 2015 14:50:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D11AC200FF for ; Tue, 21 Apr 2015 14:50:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752973AbbDUOum (ORCPT ); Tue, 21 Apr 2015 10:50:42 -0400 Received: from mail-pa0-f44.google.com ([209.85.220.44]:33326 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754541AbbDUOui (ORCPT ); Tue, 21 Apr 2015 10:50:38 -0400 Received: by paboj16 with SMTP id oj16so243264998pab.0 for ; Tue, 21 Apr 2015 07:50:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:cc:subject :content-type:content-transfer-encoding; bh=B+gRiyFuVQwxV5QM6/jHai/EuBVII+WqVyIzQ9PVEn8=; b=C9xc0LX4I7RqLMKWko7RBL41T1cHmykvmEWdjlgjlSZZ4B3o/ZotlCPkbnLxTexSHR nBIKrKm976j5Q823U3u4WvepZUSr3Ur0AQGUSjkMX44AoeRgKCohmvsQCrNks1kTo8DD 5NH2TY5DgWdvtIvYrAappfbAmPSWwqSJZYnpjXy+cekElx+wuaH5LvmxVfr+LofbKIbw wSSUL9mVnCpy8MJtudvFeEGFCUm0k+WQJTANFjNKcbmcFo/5nzqm1UjwcutRDt98rUpU qrvFYQD6RvWFHVbJwVs5eRaQMl3nI15nQv+uRTjsZbVDRAKmX0fsuyL3q5mjshVwimYD 3u9g== X-Received: by 10.70.87.231 with SMTP id bb7mr37980314pdb.70.1429627837825; Tue, 21 Apr 2015 07:50:37 -0700 (PDT) Received: from [192.168.99.7] ([104.143.41.79]) by mx.google.com with ESMTPSA id nb10sm2295671pdb.76.2015.04.21.07.50.34 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 21 Apr 2015 07:50:36 -0700 (PDT) Message-ID: <553663B7.7030506@gmail.com> Date: Tue, 21 Apr 2015 22:50:31 +0800 From: Kinglong Mee User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: "J. Bruce Fields" , "linux-nfs@vger.kernel.org" CC: kinglongmee@gmail.com Subject: [PATCH RFC] NFSD: fix cannot umounting mount points under pseudo root Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, FREEMAIL_FROM, RCVD_IN_DNSWL_HI, T_DKIM_INVALID, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP If there are some mount points(not exported for nfs) under a pseudo root, after client's operation of those entry under the root, anyone can unmount those mount points until nfsd stop. # cat /etc/exports /nfs/xfs *(rw,insecure,no_subtree_check,no_root_squash) /nfs/pnfs *(rw,insecure,no_subtree_check,no_root_squash) # ll /nfs/ total 0 drwxr-xr-x. 3 root root 84 Apr 21 22:27 pnfs drwxr-xr-x. 3 root root 84 Apr 21 22:27 test drwxr-xr-x. 2 root root 6 Apr 20 22:01 xfs # mount /dev/sde /nfs/test # df Filesystem 1K-blocks Used Available Use% Mounted on ...... /dev/sdd 1038336 32944 1005392 4% /nfs/pnfs /dev/sdc 10475520 32928 10442592 1% /nfs/xfs /dev/sde 999320 1284 929224 1% /nfs/test # mount -t nfs 127.0.0.1:/nfs/ /mnt # ll /mnt/*/ /mnt/pnfs/: total 0 -rw-r--r--. 1 root root 0 Apr 21 22:23 attr drwxr-xr-x. 2 root root 6 Apr 21 22:19 tmp /mnt/xfs/: total 0 # umount /nfs/test/ umount: /nfs/test/: target is busy (In some cases useful info about processes that use the device is found by lsof(8) or fuser(1).) I don't think that's user expect, they want umount /nfs/test/. It's caused by exports cache of nfsd holds the reference of the path (here is /nfs/test/), so, it can't umounted until nfsd stop. There is one strange thing exist, the export cache status of /nfs/test/ is CACHE_NEGATIVE, also hold the reference of the path. I think nfsd should not hold the reference when CACHE_NEGATIVE. I can't find a better way to put the reference, just path it after svc_export_update(). Any comments are welcome, thanks. Signed-off-by: Kinglong Mee --- fs/nfsd/export.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c index c3e3b6e..5595cffc7 100644 --- a/fs/nfsd/export.c +++ b/fs/nfsd/export.c @@ -793,9 +793,15 @@ svc_export_update(struct svc_export *new, struct svc_export *old) int hash = svc_export_hash(old); ch = sunrpc_cache_update(old->cd, &new->h, &old->h, hash); - if (ch) - return container_of(ch, struct svc_export, h); - else + if (ch) { + struct svc_export *exp = container_of(ch, struct svc_export, h); + if (test_bit(CACHE_NEGATIVE, &exp->h.flags)) { + path_put(&exp->ex_path); + exp->ex_path.mnt = NULL; + exp->ex_path.dentry = NULL; + } + return exp; + } else return NULL; }