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.
v1 --> v2,
1. Adds an option named "allow_umount" for exports allowing user
un-mounting the filesystem where nfsd exports base on.
2. New helpers path_get_pin/path_put_unpin for path pin.
3. Update exports according to the "allow_umount" option.
Kinglong Mee (5):
fs_pin: Fix uninitialized value in fs_pin
fs_pin: Export functions for specific filesystem
path: New helpers path_get_pin/path_put_unpin for path pin
sunrpc: New helper cache_force_expire for cache cleanup
nfsd: Allows user un-mounting filesystem where nfsd exports base on
fs/fs_pin.c | 3 +++
fs/namei.c | 26 ++++++++++++++++++++
fs/nfsd/export.c | 52 ++++++++++++++++++++++++++++++++--------
fs/nfsd/export.h | 11 ++++++++-
include/linux/fs_pin.h | 6 +++++
include/linux/path.h | 4 ++++
include/linux/sunrpc/cache.h | 11 +++++++++
include/uapi/linux/nfsd/export.h | 3 ++-
8 files changed, 104 insertions(+), 12 deletions(-)
--
2.4.1
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