Errors during a simple mount storm test

Errors during a simple mount storm test

[Shehjar Tikoo]

Hi All

The shell command below is probably not applicable to
all real world setups but I wanted to check it out nonetheless.
The problem is with the following command that is supposed
run a mount-umount loop:

$ while [ true ]; do echo sending; mount localhost:/test -o 
noacl,nolock,tcp,mountproto=tcp /mnt;umount  /mnt; done

For the first hundred iterations, it works fine but then starts
spewing errors with the mount command failing. For eg.
the output looks like below:

sending
sending
sending
sending
sending
sending
sending
sending
sending
sending
sending
sending
mount.nfs: mount system call failed
umount: /mnt: not mounted
sending
mount.nfs: mount system call failed
umount: /mnt: not mounted
sending
mount.nfs: mount system call failed
umount: /mnt: not mounted
sending
mount.nfs: mount system call failed
umount: /mnt: not mounted

Any ideas why the mount sequence stops abruptly?
There dont seem to be any relevant messages in the
dmesg output either.

The client and server are on the same machine:
Linux indus 2.6.31-17-generic Ubuntu SMP x86_64 GNU/Linux

I have verified through wireshark that the server is not
receiving any mount requests once the mount command start
failing. Instead there are only successful GETPORT requests
for the MOUNTv3 program.

Thanks
-Shehjar

Re: Errors during a simple mount storm test

[Trond Myklebust]

On Fri, 2010-02-05 at 01:45 +0530, Shehjar Tikoo wrote: 
> Hi All
> 
> The shell command below is probably not applicable to
> all real world setups but I wanted to check it out nonetheless.
> The problem is with the following command that is supposed
> run a mount-umount loop:
> 
> $ while [ true ]; do echo sending; mount localhost:/test -o 
> noacl,nolock,tcp,mountproto=tcp /mnt;umount  /mnt; done
> 
> For the first hundred iterations, it works fine but then starts
> spewing errors with the mount command failing. For eg.
> the output looks like below:
> 
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> sending
> mount.nfs: mount system call failed
> umount: /mnt: not mounted
> sending
> mount.nfs: mount system call failed
> umount: /mnt: not mounted
> sending
> mount.nfs: mount system call failed
> umount: /mnt: not mounted
> sending
> mount.nfs: mount system call failed
> umount: /mnt: not mounted
> 
> Any ideas why the mount sequence stops abruptly?
> There dont seem to be any relevant messages in the
> dmesg output either.
> 
> The client and server are on the same machine:
> Linux indus 2.6.31-17-generic Ubuntu SMP x86_64 GNU/Linux
> 
> I have verified through wireshark that the server is not
> receiving any mount requests once the mount command start
> failing. Instead there are only successful GETPORT requests
> for the MOUNTv3 program.

"netstat -t" will probably show you that all your free ports in the
range 0-1023 are now in the TIME_WAIT state. This again means that you
have to wait a couple of minutes for the TIME_WAITs to expire before you
can try again.

So basically, it is a case of your test being flawed.

Trond

Re: Errors during a simple mount storm test

[Shehjar Tikoo]

Trond Myklebust wrote:
> On Fri, 2010-02-05 at 01:45 +0530, Shehjar Tikoo wrote: 
>> Hi All
>>
>> The shell command below is probably not applicable to
>> all real world setups but I wanted to check it out nonetheless.
>> The problem is with the following command that is supposed
>> run a mount-umount loop:
>>
>> $ while [ true ]; do echo sending; mount localhost:/test -o 
>> noacl,nolock,tcp,mountproto=tcp /mnt;umount  /mnt; done
>>
>> For the first hundred iterations, it works fine but then starts
>> spewing errors with the mount command failing. For eg.
>> the output looks like below:
>>
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> sending
>> mount.nfs: mount system call failed
>> umount: /mnt: not mounted
>> sending
>> mount.nfs: mount system call failed
>> umount: /mnt: not mounted
>> sending
>> mount.nfs: mount system call failed
>> umount: /mnt: not mounted
>> sending
>> mount.nfs: mount system call failed
>> umount: /mnt: not mounted
>>
>> Any ideas why the mount sequence stops abruptly?
>> There dont seem to be any relevant messages in the
>> dmesg output either.
>>
>> The client and server are on the same machine:
>> Linux indus 2.6.31-17-generic Ubuntu SMP x86_64 GNU/Linux
>>
>> I have verified through wireshark that the server is not
>> receiving any mount requests once the mount command start
>> failing. Instead there are only successful GETPORT requests
>> for the MOUNTv3 program.
> 
> "netstat -t" will probably show you that all your free ports in the
> range 0-1023 are now in the TIME_WAIT state. This again means that you
> have to wait a couple of minutes for the TIME_WAITs to expire before you
> can try again.
> 
> So basically, it is a case of your test being flawed.

Thanks!
I'll to resort to using noresvport in that case.

-Shehjar

> 
> Trond
>