The file doesn't exist, but when specifying the complete pathname,
nfsv4 thinks that the file already exists.
[...]
# mv /mnt/nfs/B/f /mnt/nfs/A/f
mv: ‘/mnt/nfs/B/f’ and ‘/mnt/nfs/A/f’ are the same file
# ls -l /mnt/nfs/A/f
-rw-r--r--. 1 nfsnobody nfsnobody 0 May 29 01:59 /mnt/nfs/A/f
# ls -l /mnt/nfs/A/
total 0
[...]
Things I've tried:
1. dropping cache
2. using noac
What mv tries to do is mv ‘/mnt/nfs/B/f’ ‘/mnt/nfs/A/f’, it finds
that the file already exists. This is a bug.
Enabling rpcdbug logs for
# rpcdebug -m nfs -s pagecache lookupcache dircache fscache
[47821.556171] NFS: nfs_lookup_revalidate(A/f) is valid
Best,
- Achilles
---
Reproducer by my colleague @Takayuki Nagata
Steps to Reproduce:
1. Mount a NFSv4 volume with noac on node1 and node2.
[root@node1 ~]# mount -o noac server:/srv/export /mnt/nfs
[root@node2 ~]# mount -o noac server:/srv/export /mnt/nfs
2. Create directories and a file.
[root@node1 ~]# mkdir /mnt/nfs/{A,B}; touch /mnt/nfs/A/f
3. Move the file from A to B on the node1.
[root@node1 ~]# mv /mnt/nfs/A/f /mnt/nfs/B/
4. cat the file on the node2, and move it from B to A.
[root@node2 ~]# cat /mnt/nfs/B/f; mv /mnt/nfs/B/f /mnt/nfs/A/
5. Move it again from A to B on the node1.
[root@node1 ~]# mv /mnt/nfs/A/f /mnt/nfs/B/
6. cat the file again on the node2, and move it from B to A again.
[root@node2 ~]# cat /mnt/nfs/B/f; mv /mnt/nfs/B/f /mnt/nfs/A/
mv: `/mnt/nfs/B/f' and `/mnt/nfs/A/f' are the same file
Best,
- Achilles
---
On Wed, May 29, 2019 at 10:09 PM Benjamin Coddington
<bcodding@xxxxxxxxxx> wrote:
>
> On 29 May 2019, at 12:21, Trond Myklebust wrote:
>
> > On Wed, 2019-05-29 at 11:08 -0400, Benjamin Coddington wrote:
> >> Hey, here's an interesting one, this seems wrong:
> >>
> >> [root@fedora27_c2_v5 ~]# mkdir /mnt/one
> >> [root@fedora27_c2_v5 ~]# mkdir /mnt/two
> >> [root@fedora27_c2_v5 ~]# mount -t nfs -ov4,noac,sec=sys,nosharecache
> >> 192.168.122.50:/exports /mnt/one
> >> [root@fedora27_c2_v5 ~]# mount -t nfs -ov4,noac,sec=sys,nosharecache
> >> 192.168.122.50:/exports /mnt/two
> >> [root@fedora27_c2_v5 ~]# mkdir /mnt/one/A
> >> [root@fedora27_c2_v5 ~]# mkdir /mnt/one/B
> >> [root@fedora27_c2_v5 ~]# touch /mnt/one/A/foo
> >> [root@fedora27_c2_v5 ~]# cat /mnt/two/A/foo
> >> [root@fedora27_c2_v5 ~]# mv /mnt/two/A/foo /mnt/two/B/foo
> >> [root@fedora27_c2_v5 ~]# mv /mnt/one/B/foo /mnt/one/A/foo
> >> [root@fedora27_c2_v5 ~]# cat /mnt/two/A/foo
> >> [root@fedora27_c2_v5 ~]# stat /mnt/two/B/foo
> >> File: /mnt/two/B/foo
> >> Size: 0 Blocks: 0 IO Block: 262144 regular
> >> empty
> >> file
> >> Device: 2fh/47d Inode: 439603 Links: 1
> >> Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid:
> >> ( 0/ root)
> >> Context: system_u:object_r:nfs_t:s0
> >> Access: 2019-05-28 14:00:18.929663705 -0400
> >> Modify: 2019-05-28 14:00:18.929663705 -0400
> >> Change: 2019-05-28 14:00:58.990124573 -0400
> >> Birth: -
> >>
> >>
> >> ^^ that lstat should return -ENOENT.
> >>
> >> I think we detect a stale directory by comparing the directory's
> >> change_attr with the dentry's d_time. But, here's a case where they
> >> are
> >> the same!
> >>
> >> Am I wrong about this, or any clever ideas to catch this case?
> >>
> >
> > When you are mounting using 'nosharecache' then you are making /mnt/one
> > and /mnt/two act as if they are different filesystems. The fact that
> > they are the same on the server, means you are setting up a testcase
> > where the files+directories are acting like the "changing on the
> > server" case as far as the client is concerned.
> >
> > If you want the above to work in a sane fashion, then just don't use
> > 'nosharecache'.
>
> That was deliberate to avoid having to show two clients in the example..
> sorry, I should have been more explicit.
>
> I think the client should be able to detect this case, since it can see an
> updated change_attr for that particular directory -- that is
> "/mnt/two/B/foo", but maybe it needs to compare the change_attr to its
> previous value instead of comparing it to the child's d_time?
>
> The person who reported it has some workload that flips files between
> directories on separate clients, and doesn't like it when `mv` reports
> "source and destination are the same file".
>
> Ben
