Bug 1946346

commit c547ad481dca5bc0b0a2e365ebcff3439848f664 
Author: Rohan Sable <rsable>
Date:   Mon Feb 14 11:15:22 2022 -0500

    mount.nfs Fix error reporting for already mounted shares

This problem doesn't get fixed after that patch applied.

[root@ ~]# systemctl restart nfs-server
[root@ ~]# cat /proc/fs/nfsd/versions
-2 +3 -4 -4.0 -4.1 -4.2
[root@ ~]# mount 127.0.0.1:/export_test/ /mnt_test/
[root@ ~]# nfsstat -m
/mnt_test from 127.0.0.1:/export_test/
 Flags: rw,relatime,vers=3,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=127.0.0.1,mountvers=3,mountport=20048,mountproto=udp,local_lock=none,addr=127.0.0.1

[root@ ~]# mount 127.0.0.1:/export_test/ /mnt_test/
mount.nfs: Protocol not supported
[root@ ~]# echo $?
32
[root@ ~]# rpm -q nfs-utils
nfs-utils-2.3.3-49.el8.x86_64
[root@ ~]#

Verified in nfs-utils-2.3.3-50.el8 the EBUSY error emits (in verbose mode).
By default it's hided due to https://patchwork.kernel.org/project/linux-nfs/patch/877fi2raey.fsf@notabene.neil.brown.name/

[root@yoyang-rhel-860-202202123 ~]# cat /proc/fs/nfsd/versions
-2 +3 -4 -4.0 -4.1 -4.2
[root@yoyang-rhel-860-202202123 ~]# mount 127.0.0.1:/export_test/ /mnt_test/
[root@yoyang-rhel-860-202202123 ~]# nfsstat -m
/mnt_test from 127.0.0.1:/export_test/
 Flags: rw,relatime,vers=3,rsize=262144,wsize=262144,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=127.0.0.1,mountvers=3,mountport=20048,mountproto=udp,local_lock=none,addr=127.0.0.1

[root@yoyang-rhel-860-202202123 ~]# mount 127.0.0.1:/export_test/ /mnt_test/
[root@yoyang-rhel-860-202202123 ~]# echo $?
0
[root@yoyang-rhel-860-202202123 ~]# mount 127.0.0.1:/export_test/ /mnt_test/ -vvv
mount.nfs: timeout set for Mon Feb 21 00:05:31 2022
mount.nfs: trying text-based options 'vers=4.2,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs: mount(2): Protocol not supported
mount.nfs: trying text-based options 'vers=4,minorversion=1,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs: mount(2): Protocol not supported
mount.nfs: trying text-based options 'vers=4,addr=127.0.0.1,clientaddr=127.0.0.1'
mount.nfs: mount(2): Protocol not supported
mount.nfs: trying text-based options 'addr=127.0.0.1'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 127.0.0.1 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 127.0.0.1 prog 100005 vers 3 prot UDP port 20048
mount.nfs: mount(2): Device or resource busy
[root@yoyang-rhel-860-202202123 ~]# rpm -q nfs-utils
nfs-utils-2.3.3-50.el8.x86_64
[root@yoyang-rhel-860-202202123 ~]#

Have verified in nfs-utils-2.3.3-50.el8 i.e. https://beaker.engineering.redhat.com/jobs/6324044

Including "EACCES" might lead to Bug 1709963 recurrence.
And the olderrno was added to fix that.

[16:57:26 root@ ~~]# exportfs -i 127.0.0.1:/export -o rw,no_root_squash,fsid=0
[16:57:26 root@ ~~]# mount 127.0.0.1:/notexistdir /mnt/nfsmp
mount.nfs: access denied by server while mounting 127.0.0.1:/notexistdir
           ^^^^^^^^^^^^^^
[16:57:27 root@ ~~]# mount -t nfs4 127.0.0.1:/notexistdir /mnt/nfsmp
mount.nfs4: mounting 127.0.0.1:/notexistdir failed, reason given by server: No such file or directory

(In reply to Yongcheng Yang from comment #27)
> Including "EACCES" might lead to Bug 1709963 recurrence.
> And the olderrno was added to fix that.
> 
> [16:57:26 root@ ~~]# exportfs -i 127.0.0.1:/export -o
> rw,no_root_squash,fsid=0
> [16:57:26 root@ ~~]# mount 127.0.0.1:/notexistdir /mnt/nfsmp
> mount.nfs: access denied by server while mounting 127.0.0.1:/notexistdir
>            ^^^^^^^^^^^^^^
I'm thinking this is ok.... but if you think it is a problem, please
open up another bz...

(In reply to Steve Dickson from comment #28)
> (In reply to Yongcheng Yang from comment #27)
> > Including "EACCES" might lead to Bug 1709963 recurrence.
> > And the olderrno was added to fix that.
> > 
> > [16:57:26 root@ ~~]# exportfs -i 127.0.0.1:/export -o
> > rw,no_root_squash,fsid=0
> > [16:57:26 root@ ~~]# mount 127.0.0.1:/notexistdir /mnt/nfsmp
> > mount.nfs: access denied by server while mounting 127.0.0.1:/notexistdir
> >            ^^^^^^^^^^^^^^
> I'm thinking this is ok.... but if you think it is a problem, please
> open up another bz...

I don't know the background of filing Bug 1709963 thus not sure if this is a problem for someone.

Let's keep this in mind and we can jump back in the future. Thanks!

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (nfs-utils bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2022:2025