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    SubjectRe: 3.4. sunrpc oops during shutdown
    Date
    On Fri, 2012-05-25 at 12:12 +0400, Stanislav Kinsbursky wrote:
    > On 21.05.2012 22:03, Myklebust, Trond wrote:
    > > On Mon, 2012-05-21 at 13:14 -0400, Dave Jones wrote:
    > >> Tried to shutdown a machine, got this, and a bunch of hung processes.
    > >> There was one NFS mount mounted at the time.
    > >>
    > >> Dave
    > >>
    > >> BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
    > >> IP: [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
    > >> PGD 1434c4067 PUD 144964067 PMD 0
    > >> Oops: 0000 [#1] PREEMPT SMP
    > >> CPU 4
    > >> Modules linked in: ip6table_filter(-) ip6_tables nfsd nfs fscache auth_rpcgss nfs_acl lockd ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6
    > >>
    > >> Pid: 6946, comm: ntpd Not tainted 3.4.0+ #13
    > >> RIP: 0010:[<ffffffffa01191df>] [<ffffffffa01191df>] svc_destroy+0x1f/0x140 [sunrpc]
    > >> RSP: 0018:ffff880143c65c48 EFLAGS: 00010286
    > >> RAX: 0000000000000000 RBX: ffff880142cd41a0 RCX: 0000000000000006
    > >> RDX: 0000000000000040 RSI: ffff880143105028 RDI: ffff880142cd41a0
    > >> RBP: ffff880143c65c58 R08: 0000000000000000 R09: 0000000000000001
    > >> R10: 0000000000000000 R11: 0000000000000000 R12: ffff88013bc5a148
    > >> R13: ffff880140981658 R14: ffff880142cd41a0 R15: ffff880146c88000
    > >> FS: 00007fdc0382a740(0000) GS:ffff880149400000(0000) knlGS:0000000000000000
    > >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    > >> CR2: 0000000000000028 CR3: 0000000036cbb000 CR4: 00000000001407e0
    > >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    > >> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    > >> Process ntpd (pid: 6946, threadinfo ffff880143c64000, task ffff880143104940)
    > >> Stack:
    > >> ffff880140981660 ffff88013bc5a148 ffff880143c65c88 ffffffffa01193a6
    > >> 0000000000000000 ffff88013e566020 ffff88013e565f28 ffff880146ee6ac0
    > >> ffff880143c65ca8 ffffffffa024f403 ffff880143c65ca8 ffff880143d3a4f8
    > >> Call Trace:
    > >> [<ffffffffa01193a6>] svc_exit_thread+0xa6/0xb0 [sunrpc]
    > >> [<ffffffffa024f403>] nfs_callback_down+0x53/0x90 [nfs]
    > >> [<ffffffffa021642e>] nfs_free_client+0xfe/0x120 [nfs]
    > >> [<ffffffffa02185df>] nfs_put_client+0x29f/0x420 [nfs]
    > >> [<ffffffffa02184e0>] ? nfs_put_client+0x1a0/0x420 [nfs]
    > >> [<ffffffffa021962f>] nfs_free_server+0x16f/0x2e0 [nfs]
    > >> [<ffffffffa02194e3>] ? nfs_free_server+0x23/0x2e0 [nfs]
    > >> [<ffffffffa022363c>] nfs4_kill_super+0x3c/0x50 [nfs]
    > >> [<ffffffff811ad67c>] deactivate_locked_super+0x3c/0xa0
    > >> [<ffffffff811ae29e>] deactivate_super+0x4e/0x70
    > >> [<ffffffff811ccba4>] mntput_no_expire+0xb4/0x100
    > >> [<ffffffff811ccc16>] mntput+0x26/0x40
    > >> [<ffffffff811cd597>] release_mounts+0x77/0x90
    > >> [<ffffffff811cefc6>] put_mnt_ns+0x66/0x80
    > >> [<ffffffff81078dff>] free_nsproxy+0x1f/0xb0
    > >> [<ffffffff8107905e>] switch_task_namespaces+0x5e/0x70
    > >> [<ffffffff81079080>] exit_task_namespaces+0x10/0x20
    > >> [<ffffffff8104e90e>] do_exit+0x4ee/0xb80
    > >> [<ffffffff81639c0a>] ? retint_swapgs+0xe/0x13
    > >> [<ffffffff8104f2ef>] do_group_exit+0x4f/0xc0
    > >> [<ffffffff8104f377>] sys_exit_group+0x17/0x20
    > >> [<ffffffff81641352>] system_call_fastpath+0x16/0x1b
    > >> Code: 48 8b 5d f0 4c 8b 65 f8 c9 c3 66 90 55 48 89 e5 41 54 53 66 66 66 66 90 65 48 8b 04 25 80 ba 00 00 48 8b 80 50 05 00 00 48 89 fb<4c> 8b 60 28 8b 47 58 85 c0 0f 84 ec 00 00 00 83 e8 01 85 c0 89
    > >
    > > Aside from the fact that the current net_namespace is not guaranteed to
    > > exist when we are called from free_nsproxy, svc_destroy() looks
    > > seriously broken:
    >
    > Trond, looks like you are mistaken here.
    > Any process holds references to all namespaces it belong to (copy_net_ns()
    > increase usage counter). And network namespace is released after mount namespace
    > in free_nsproxy.

    That doesn't help you though. switch_task_namespaces will have already
    set current->nsproxy to NULL, which is why we Oops when we try to read
    current->nsproxy->net_ns in svc_exit_thread().

    > >
    > > * On the one hand it is trying to free struct svc_serv (and
    > > presumably all structures owned by struct svc_serv).
    > > * On the other hand, it tries to pass a parameter to
    > > svc_close_net() saying "please don't free structures on my
    > > sv_tempsocks, or sv_permsocks list unless they match this net
    > > namespace".
    > >
    >
    > I've sent patches, which moves svc_shutdown_net() from svc_destroy() ("SUNRPC:
    > separate per-net data creation from service").
    > with this patch set it's assumed, that per-net resources will be created or
    > released prior to service creation and destruction.

    Are those patches appropriate for inclusion in the stable kernel series
    so that we can fix 3.4?

    --
    Trond Myklebust
    Linux NFS client maintainer

    NetApp
    Trond.Myklebust@netapp.com
    www.netapp.com

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