Re: NFS mounts being mounted read-only depending upon mount order???

[Michael Walker <Michael.Walker@Cassatt.COM>]

All,

Any insights on this?

I did find the following post from Trond which appears

   http://lkml.org/lkml/2006/10/18/264

Which seems to imply that this is a 'feature' and not
a 'bug'?  Is that true - or have I missed something?


Thanx,
   _Mike_


Michael Walker wrote:
> 
> All,
> 
> I'm having problems with the latest version of FC5 which
> contains kernel 2.6.18 - the problem is that NFS mounts
> of read-write file-systems are being mounted read-only, sometimes.
> 
> Whether a mount is mounted read-only or read-write seems
> to very depending upon what other directories were
> mounted from the same server and with what options.
> 
> Take the following file-systems exported from my
> Linux Server server:
> 
>    root@polyslo:/proc/fs/nfs# cat /etc/exports
>    /disk1/dir_ro   *(ro,no_root_squash,sync,wdelay,no_subtree_check)
>    /disk1/dir_rw   *(rw,no_root_squash,sync,wdelay,no_subtree_check)
>    root@polyslo:/proc/fs/nfs# showmount -e 10.20.20.48
>    Export list for 10.20.20.48:
>    /disk1/dir_rw *
>    /disk1/dir_ro *
>    root@polyslo:/proc/fs/nfs#
> 
> If I now do the following mounts (in this order):
> 
>    # Mount initial directory read-only - this is intentional
>    mount -t nfs -o ro 10.20.20.48:/disk1/dir_ro /tmp/dir_ro
> 
>    # Attempt to mount second directory read-write
>    mount -t nfs -o rw 10.20.20.48:/disk1/dir_rw /tmp/dir_rw
> 
>    # Now I attempt to touch a file in the rw directory:
>    [root@vt-1 tmp]# touch /tmp/dir_rw/hello
>    touch: cannot touch `/tmp/dir_rw/hello': Read-only file system
> 
>    # And if I take a look in the /proc/mounts directory - I see
>    # that the directory was truly mounted read-only
> 
>    [root@vt-1 tmp]# grep 10.20.20.48 /proc/mounts
>    10.20.20.48:/disk1/dir_ro /tmp/dir_ro nfs 
> ro,vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=10.20.20.48 
> 0 0
>    10.20.20.48:/disk1/dir_rw /tmp/dir_rw nfs 
> ro,vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=10.20.20.48 
> 0 0
>    [root@vt-1 tmp]#
> 
> The above seems wrong to me - can someone clarify what's going on.
> I know that this is new behavior that was not true in the past.  My
> RHEL_4U4 server running 2.6.9 kernel does not have this problem.
> 
> Notice that if I change the order of the mounts I get different behavior:
> 
>    # Initially mount the read-write directory:
>    mount -t nfs -o rw 10.20.20.48:/disk1/dir_rw /tmp/dir_rw
> 
>    # Then mount the read-only directory:
>    mount -t nfs -o ro 10.20.20.48:/disk1/dir_ro /tmp/dir_ro
> 
>    # Now the directories are mounted as I wish, I can write to the
>    # read-write mount:
>    [root@vt-1 tmp]# touch /tmp/dir_rw/hello
>    [root@vt-1 tmp]#
> 
>    # And the read-only directory is read-only:
>    [root@vt-1 tmp]# touch /tmp/dir_ro/hello
>    touch: cannot touch `/tmp/dir_ro/hello': Read-only file system
>    [root@vt-1 tmp]#
> 
>    # And the /proc/mounts file reflects the states I expect
>    [root@vt-1 tmp]# grep 10.20.20.48 /proc/mounts
>    10.20.20.48:/disk1/dir_rw /tmp/dir_rw nfs 
> rw,vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=10.20.20.48 
> 0 0
>    10.20.20.48:/disk1/dir_ro /tmp/dir_ro nfs 
> rw,vers=3,rsize=32768,wsize=32768,hard,proto=tcp,timeo=600,retrans=2,sec=sys,addr=10.20.20.48 
> 0 0
>    [root@vt-1 tmp]#
> 
> 
> Note that previously the order did not matter and the permissions
> always reflected the permissions of the individual mount requests.
> 
> If someone could provide insights on what's going on above that
> would be great.  This is a artificial test case - but it's actually
> hitting code we have in production and will be a significant
> issue for us.
> 
> Thanx much!
> 
> _Mike_


-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs