From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kinglong Mee Subject: [PATCH 0/4] NFSD: Pin to vfsmount instead of mntget for export cache Date: Wed, 06 May 2015 21:18:19 +0800 Message-ID: <554A149B.5060102@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: NeilBrown , Trond Myklebust , kinglongmee@gmail.com To: "J. Bruce Fields" , Al Viro , linux-fsdevel@vger.kernel.org, "linux-nfs@vger.kernel.org" Return-path: Received: from mail-pd0-f178.google.com ([209.85.192.178]:33667 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751068AbbEFNS0 (ORCPT ); Wed, 6 May 2015 09:18:26 -0400 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: If there are some mount points(not exported for nfs) under pseudo root, after client's operation of those entry under the root, anyone *can't* unmount those mount points until export cache expired. # 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 be umounted. The patch site using fs_pin instead of mntget for export cache, user at nfs server can unmount any mount points includes exported for nfs. Maybe, only umounted for unexported mount points is better? [PATCH 1/4] fs_pin: Fix uninitialized value in fs_pin [PATCH 2/4] fs_pin: Export functions for specific filesystem [PATCH 3/4] sunrpc: New helper cache_force_expire for cache cleanup [PATCH 4/4] nfsd: Pin to vfsmnt instead of mntget Kinglong Mee (4): fs_pin: initialize done to zero fs_pin: export functions for nactive filesystem sunrpc: new helper cache_force_expire for deleting a cache nfsd: pin to mnt insteads mntget fs/fs_pin.c | 3 +++ fs/nfsd/export.c | 37 ++++++++++++++++++++++++++++++------- fs/nfsd/export.h | 10 +++++++++- include/linux/fs_pin.h | 1 + include/linux/sunrpc/cache.h | 11 +++++++++++ 5 files changed, 54 insertions(+), 8 deletions(-) -- 2.4.0