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	Fri, 17 Apr 2015 17:22:38 -0400
Date: Fri, 17 Apr 2015 17:22:36 -0400
From: "J. Bruce Fields" <bfields@fieldses.org>
To: Kinglong Mee <kinglongmee@gmail.com>
Cc: Giuseppe Cantavenera <giuseppe.cantavenera.ext@nokia.com>,
        linux-nfs@vger.kernel.org, alexander.sverdlin@nokia.com,
        Lorenzo Restelli <lorenzo.restelli.ext@nokia.com>
Subject: Re: [PATCH] nfsd: fix: prevent BUG_ON registering rpc_pipefs_event
 for notifications only after nfsd_net_id is valid
Message-ID: <20150417212236.GA28426@fieldses.org>
References: <1429266331-2408-1-git-send-email-giuseppe.cantavenera.ext@nokia.com>
 <553113AD.6030702@gmail.com>
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On Fri, Apr 17, 2015 at 10:07:41PM +0800, Kinglong Mee wrote:
> On 4/17/2015 6:25 PM, Giuseppe Cantavenera wrote:
> > nfsd triggered a BUG_ON in net_generic(...) when rpc_pipefs_event(...)
> > in fs/nfsd/nfs4recover.c was called before assigning ntfsd_net_id.
> > The following was observed on a MIPS 32-core processor:
> > kernel: Call Trace:
> > kernel: [<ffffffffc00bc5e4>] rpc_pipefs_event+0x7c/0x158 [nfsd]
> > kernel: [<ffffffff8017a2a0>] notifier_call_chain+0x70/0xb8
> > kernel: [<ffffffff8017a4e4>] __blocking_notifier_call_chain+0x4c/0x70
> > kernel: [<ffffffff8053aff8>] rpc_fill_super+0xf8/0x1a0
> > kernel: [<ffffffff8022204c>] mount_ns+0xb4/0xf0
> > kernel: [<ffffffff80222b48>] mount_fs+0x50/0x1f8
> > kernel: [<ffffffff8023dc00>] vfs_kern_mount+0x58/0xf0
> > kernel: [<ffffffff802404ac>] do_mount+0x27c/0xa28
> > kernel: [<ffffffff80240cf0>] SyS_mount+0x98/0xe8
> > kernel: [<ffffffff80135d24>] handle_sys64+0x44/0x68
> > kernel:
> > kernel:
> >         Code: 0040f809  00000000  2e020001 <00020336> 3c12c00d  3c02801a  de100000  6442eb98  0040f809
> > kernel: ---[ end trace 7471374335809536 ]---
> > 
> > Fixed this behaviour by calling register_pernet_subsys(&nfsd_net_ops) before
> > registering rpc_pipefs_event(...) with the notifier chain.
> > 
> > Signed-off-by: Giuseppe Cantavenera <giuseppe.cantavenera.ext@nokia.com>
> > Signed-off-by: Lorenzo Restelli <lorenzo.restelli.ext@nokia.com>
> 
> Make sense,
> Reviewed-by: Kinglong Mee <kinglongmee@gmail.com>

Thanks, applying.--b.

> 
> > ---
> >  fs/nfsd/nfsctl.c | 16 ++++++++--------
> >  1 file changed, 8 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> > index f34d9de..3ee92a4 100644
> > --- a/fs/nfsd/nfsctl.c
> > +++ b/fs/nfsd/nfsctl.c
> > @@ -1170,15 +1170,15 @@ static int __init init_nfsd(void)
> >  	int retval;
> >  	printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@monad.swb.de).\n");
> >  
> > -	retval = register_cld_notifier();
> > -	if (retval)
> > -		return retval;
> >  	retval = register_pernet_subsys(&nfsd_net_ops);
> >  	if (retval < 0)
> > -		goto out_unregister_notifier;
> > -	retval = nfsd4_init_slabs();
> > +		return retval;
> > +	retval = register_cld_notifier();
> >  	if (retval)
> >  		goto out_unregister_pernet;
> > +	retval = nfsd4_init_slabs();
> > +	if (retval)
> > +		goto out_unregister_notifier;
> >  	nfs4_state_init();
> >  	retval = nfsd_fault_inject_init(); /* nfsd fault injection controls */
> >  	if (retval)
> > @@ -1206,10 +1206,10 @@ out_free_stat:
> >  	nfsd_fault_inject_cleanup();
> >  out_free_slabs:
> >  	nfsd4_free_slabs();
> > -out_unregister_pernet:
> > -	unregister_pernet_subsys(&nfsd_net_ops);
> >  out_unregister_notifier:
> >  	unregister_cld_notifier();
> > +out_unregister_pernet:
> > +	unregister_pernet_subsys(&nfsd_net_ops);
> >  	return retval;
> >  }
> >  
> > @@ -1223,8 +1223,8 @@ static void __exit exit_nfsd(void)
> >  	nfsd4_free_slabs();
> >  	nfsd_fault_inject_cleanup();
> >  	unregister_filesystem(&nfsd_fs_type);
> > -	unregister_pernet_subsys(&nfsd_net_ops);
> >  	unregister_cld_notifier();
> > +	unregister_pernet_subsys(&nfsd_net_ops);
> >  }
> >  
> >  MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");
> >