Re: 2.6.18-rc4-mm1

[Trond Myklebust <trond.myklebust@fys.uio.no>]

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On Tue, 2006-08-15 at 17:55 +0100, David Howells wrote:
> Trond Myklebust <trond.myklebust@fys.uio.no> wrote:
> 
> > Could you try pulling afresh from the NFS git tree? I've fixed up a couple
> > of issues in which rpc_pipefs was corrupting the dcache,
> 
> Which patches hold those fixes?  I'm seeing:
> 
> 	BUG: atomic counter underflow at:
> 	 [<c01d5b05>] _atomic_dec_and_lock+0x1d/0x30
> 	 [<c0169bd3>] dput+0x22/0x145
> 	 [<c8a2f726>] rpc_destroy_client+0xd9/0xee [sunrpc]
> 	 [<c8a2f89e>] rpc_shutdown_client+0xea/0xf1 [sunrpc]
> 	 [<c8a2f89e>] rpc_shutdown_client+0xea/0xf1 [sunrpc]
> 	 [<c886d842>] nfs_free_client+0x95/0xdd [nfs]
> 	 [<c886db38>] nfs_free_server+0xa9/0xd9 [nfs]
> 	 [<c8873fae>] nfs_kill_super+0xc/0x14 [nfs]
> 	 [<c015c033>] deactivate_super+0x4a/0x5d
> 	 [<c016df3e>] sys_umount+0x1d3/0x1f1
> 	 [<c016ac98>] destroy_inode+0x36/0x45
> 	 [<c0169bd3>] dput+0x22/0x145
> 	 [<c0157889>] __fput+0x146/0x170
> 	 [<c016cf48>] mntput_no_expire+0x11/0x59
> 	 [<c016df73>] sys_oldumount+0x17/0x1a
> 	 [<c0102b3f>] syscall_call+0x7/0xb
> 	 =======================
> 
> And I'm wondering if that's due to that problem.
> 
> I've applied the patch to fix the resource counting that's at the head of your
> git tree.

See attached mail. Alex confirmed that it fixes the corruption problems
he is seeing.

Cheers,
  Trond

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From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Alex Polvi <polvi@google.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCHv3] sunrpc/auth_gss: NULL pointer deref in gss_pipe_release()
Date: Mon, 14 Aug 2006 18:46:39 -0400
Message-ID: <1155595592.5656.22.camel@localhost>

On Mon, 2006-08-14 at 16:34 -0400, Alex Polvi wrote:
> On 8/14/06, Alex Polvi <polvi@google.com> wrote:
> > Here is another fix. It is quite silly, but clnt->cl_auth is set to
> > NULL in rpc_destroy_client(), then eventually referenced in
> > gss_release_pipe() via rpc_rmdir(). Simply removing the clnt->cl_auth
> > = NULL from clnt.c fixes the issue. I'm still trying to understand the
> > subsystem, but it seems like rpc_rmdir is being correctly called to
> > clean up because of the weirdness with umount -l and the nfs server
> > being turned on and off. Does that seem correct? Or is this still just
> > covering up some other part of the code being sloppy cleaning up?
> 
> Also, I just want to make it clear that I do not think this is the
> proper fix. It is just pointing out that we intentionally set cl_auth
> to NULL, then reference it.

OK. I think I've finally managed to clean up the various interactions
with rpc_pipefs. I've uploaded a series of patches on the NFS client
website. See

  http://client.linux-nfs.org/Linux-2.6.x/2.6.18-rc4/

The relevant patches are

linux-2.6.18-006-fix_rpc_unlink.dif: 
        
        From: Trond Myklebust <Trond.Myklebust@netapp.com>
        
        SUNRPC: make rpc_unlink() take a dentry argument instead of a
        path
        
        Signe-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
        
linux-2.6.18-007-fix_rpc_rmdir.dif: 
        
        From: Trond Myklebust <Trond.Myklebust@netapp.com>
        
        NFS: clean up rpc_rmdir
        
        Make it take a dentry argument instead of a path
        
        Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
        
linux-2.6.18-008-fix_rpc_unlink_rmdir_2.dif: 
        
        From: Trond Myklebust <Trond.Myklebust@netapp.com>
        
        SUNRPC: rpc_unlink() must check for unhashed dentries
        
        A prior call to rpc_depopulate() by rpc_rmdir() on the parent
        directory may have already called simple_unlink() on this entry.
        Add the same check to rpc_rmdir(). Also remove a redundant call
        to rpc_close_pipes() in rpc_rmdir.
        
        Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
        
linux-2.6.18-009-fix_rpc_unlink_rmdir_3.dif: 
        
        From: Trond Myklebust <Trond.Myklebust@netapp.com>
        
        SUNRPC: Fix dentry refcounting issues with users of rpc_pipefs
        
        rpc_unlink() and rpc_rmdir() will dput the dentry reference for
        you.
        
        Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

----

In addition, there is one patch that is needed in order to fix up a
related issue in the function nfs_alloc_client(), which was introduced
by David Howells' NFS superblock sharing patches.

Cheers,
  Trond