Re: 2.6.18-rc4-mm1

[Trond Myklebust]

On Tue, 2006-08-15 at 17:55 +0100, David Howells wrote:
> Trond Myklebust <trond.myklebust@xxxxxxxxxx> 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
> --- Begin Message ---
> On Mon, 2006-08-14 at 16:34 -0400, Alex Polvi wrote:
> > On 8/14/06, Alex Polvi <polvi@xxxxxxxxxx> 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@xxxxxxxxxx>
>         
>         SUNRPC: make rpc_unlink() take a dentry argument instead of a
>         path
>         
>         Signe-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>         
> linux-2.6.18-007-fix_rpc_rmdir.dif: 
>         
>         From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>         
>         NFS: clean up rpc_rmdir
>         
>         Make it take a dentry argument instead of a path
>         
>         Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>         
> linux-2.6.18-008-fix_rpc_unlink_rmdir_2.dif: 
>         
>         From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>         
>         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@xxxxxxxxxx>
>         
> linux-2.6.18-009-fix_rpc_unlink_rmdir_3.dif: 
>         
>         From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
>         
>         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@xxxxxxxxxx>
>
> ----
>
> 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
>
> --- End Message ---