[PATCH 3.4 052/146] nfsd: fix nsfd startup race triggering BUG_ON

lizf
2015-09-15T09:08:26Z

From: Giuseppe Cantavenera <giuseppe.cantavenera.ext@nokia.com>

3.4.109-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit bb7ffbf29e76b89a86ca4c3ee0d4690641f2f772 upstream.

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>
Reviewed-by: Kinlong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
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 4db777d..c8bc7ea 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1163,15 +1163,15 @@ 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)
@@ -1209,10 +1209,10 @@ 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;
}

@@ -1228,8 +1228,8 @@ 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>");
--
1.9.1