Re: Bug starting 2.6.16 - rpc: bad TCP reclen

[Razvan Gavril <razvan.g@plutohome.com>]

Razvan Gavril wrote:
> I posted on the linux kernel mailing list but got no answer till now.
>
> I have a nfs server and some diskless computers that that have there 
> root mounted via  nfs from the server. In certain situations the 
> diskless computers fail to write correctly to their nfs mounted 
> filesystem (some files get corrupted). Looking into the nfs server's 
> dmesg, i see this messages:
>
> RPC: bad TCP reclen 0x5e9c5bec (non-terminal)
> RPC: bad TCP reclen 0x29db3277 (large)
> RPC: bad TCP reclen 0x698f6ccf (large)
> RPC: bad TCP reclen 0x336160a9 (large)
> RPC: bad TCP reclen 0x773ffdff (large)
> RPC: bad TCP reclen 0x231b8d5c (non-terminal)
> RPC: bad TCP reclen 0x39902af4 (large)
> RPC: bad TCP reclen 0x6048d9cc (non-terminal)
> RPC: bad TCP reclen 0x212f7e14 (non-terminal)
>
> This errors start to happen when upgrading to 2.6.16 from 2.6.15 but the 
> problem is still present in 2.6.17 kernel. For now i tested like this:
>
> Client - Server - State
> ------------------------
> 2.6.15 - 2.6.15 - Works
> 2.6.15 - 2.6.16 - Errors
> 2.6.16 - 2.6.16 - Errors
> 2.6.16 - 2.6.17 - Errors
> 2.6.17 - 2.6.17 - Errors
>
>  From the looks of it the problem seems to be related to the nfs server 
> implemetation from the kernels newer that 2.6.15.
>
> Those corrupted writes on client + dmesg messages on the server are easy 
> to duplicate when using Debian on the client computers and running this 
> script in parallel on more that 1 client:
>
> while /bin/true ;do
>         apt-get update
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         # you can replace gdb with any other package
>         apt-get -y install gdb
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         apt-get -y remove gdb
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         sleep $(( $RANDOM % 3 ))
> done
>
> After a couple o minutes (1-5min) apt should give a segmentation fault 
> because one of its state files got corrupted (/lib/dpkg/status or 
> other). FYI, the clients DON'T have any common files/dirs so a race 
> condition in apt can't be the cause. It's easy to see that for every apt 
> segfault on the client you'll have a rpc error message on the server.
>
> I also tried with some different script to reproduce the problem, for 
> example to copy a lot of files(small, big ..) from a nfs share to 
> another but the md5sum reported that every time the copying was 
> happening without corruption so using apt is the only solution to 
> reproduce the bug for now.
>
> I'm here if you need any other info related to this problem.
>
> --
> Razvan Gavril
>
>
>
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>   
Razvan Gavril wrote:
> I posted on the linux kernel mailing list but got no answer till now.
>
> I have a nfs server and some diskless computers that that have there 
> root mounted via  nfs from the server. In certain situations the 
> diskless computers fail to write correctly to their nfs mounted 
> filesystem (some files get corrupted). Looking into the nfs server's 
> dmesg, i see this messages:
>
> RPC: bad TCP reclen 0x5e9c5bec (non-terminal)
> RPC: bad TCP reclen 0x29db3277 (large)
> RPC: bad TCP reclen 0x698f6ccf (large)
> RPC: bad TCP reclen 0x336160a9 (large)
> RPC: bad TCP reclen 0x773ffdff (large)
> RPC: bad TCP reclen 0x231b8d5c (non-terminal)
> RPC: bad TCP reclen 0x39902af4 (large)
> RPC: bad TCP reclen 0x6048d9cc (non-terminal)
> RPC: bad TCP reclen 0x212f7e14 (non-terminal)
>
> This errors start to happen when upgrading to 2.6.16 from 2.6.15 but the 
> problem is still present in 2.6.17 kernel. For now i tested like this:
>
> Client - Server - State
> ------------------------
> 2.6.15 - 2.6.15 - Works
> 2.6.15 - 2.6.16 - Errors
> 2.6.16 - 2.6.16 - Errors
> 2.6.16 - 2.6.17 - Errors
> 2.6.17 - 2.6.17 - Errors
>
>  From the looks of it the problem seems to be related to the nfs server 
> implemetation from the kernels newer that 2.6.15.
>
> Those corrupted writes on client + dmesg messages on the server are easy 
> to duplicate when using Debian on the client computers and running this 
> script in parallel on more that 1 client:
>
> while /bin/true ;do
>         apt-get update
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         # you can replace gdb with any other package
>         apt-get -y install gdb
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         apt-get -y remove gdb
>         err=$?
>         [[ $err != 0 ]] && echo "Exiting $err" && exit $err
>
>         sleep $(( $RANDOM % 3 ))
> done
>
> After a couple o minutes (1-5min) apt should give a segmentation fault 
> because one of its state files got corrupted (/lib/dpkg/status or 
> other). FYI, the clients DON'T have any common files/dirs so a race 
> condition in apt can't be the cause. It's easy to see that for every apt 
> segfault on the client you'll have a rpc error message on the server.
>
> I also tried with some different script to reproduce the problem, for 
> example to copy a lot of files(small, big ..) from a nfs share to 
> another but the md5sum reported that every time the copying was 
> happening without corruption so using apt is the only solution to 
> reproduce the bug for now.
>
> I'm here if you need any other info related to this problem.
>
>   
Can someone at least confirm this bug and give me an idea where to start 
debugging ?

Thanks

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