Re: [patch] mm: close page_mkwrite races (try 3)

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

On Sat, 2009-05-02 at 18:12 -0400, Rince wrote:
> Well...that's different.
> 
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> IP: [<ffffffffa02c8ff2>] _nfs4_do_setlk+0xe3/0x289 [nfs]
> PGD 10e4f7067 PUD 109221067 PMD 0
> Oops: 0000 [#1] SMP
> last sysfs file: /sys/devices/virtual/block/md0/md/metadata_version
> CPU 0
> Modules linked in: autofs4 coretemp hwmon nfs lockd nfs_acl
> auth_rpcgss sunrpc cachefiles fscache ipv6 cpufreq_ondemand
> acpi_cpufreq freq_table kvm_intel kvm snd_hda_codec_idt snd_hda_intel
> snd_hda_codec snd_hwdep snd_seq_dummy snd_seq_oss snd_seq_midi_event
> snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss snd_pcm cpia_usb
> e1000e snd_timer ppdev cpia snd ums_cypress parport_pc videodev
> firewire_ohci i82975x_edac usb_storage parport firewire_core i2c_i801
> edac_core v4l1_compat soundcore snd_page_alloc iTCO_wdt
> v4l2_compat_ioctl32 pcspkr i2c_core crc_itu_t iTCO_vendor_support
> raid1 [last unloaded: scsi_wait_scan]
> Pid: 29418, comm: 10.1.1.2-manage Not tainted 2.6.30-rc4 #1
> RIP: 0010:[<ffffffffa02c8ff2>]  [<ffffffffa02c8ff2>]
> _nfs4_do_setlk+0xe3/0x289 [nfs]
> RSP: 0018:ffff880102361d30  EFLAGS: 00010246
> RAX: ffff8800ce865f00 RBX: ffff88010b4b74d8 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 00000000000000d0 RDI: 0000000000000138
> RBP: ffff880102361de0 R08: ffff880126557000 R09: ffff8800b38c3900
> R10: ffffffffa02cbd1c R11: ffff880126553c00 R12: 00000000fffffff4
> R13: 0000000000000000 R14: ffff88012d42f5c0 R15: ffff88012d42f5c0
> FS:  0000000000000000(0000) GS:ffff880028023000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
> CR2: 0000000000000010 CR3: 0000000016eda000 CR4: 00000000000026e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process 10.1.1.2-manage (pid: 29418, threadinfo ffff880102360000, task
> ffff8800015b5c00)
> Stack:
>  ffff880102361d40 0000000600000001 ffff8800ce865f00 ffffffffa02cbc5c
>  0000000000000000 ffff880126555c00 ffff880102361d90 ffffffffa02db960
>  0000000000000000 ffff880128093000 0000000000000001 ffffffffa02b88aa
> Call Trace:
>  [<ffffffffa02cbc5c>] ? nfs4_open_recover_helper+0x82/0x97 [nfs]
>  [<ffffffffa02b88aa>] ? __put_nfs_open_context+0x31/0x98 [nfs]
>  [<ffffffffa02c9646>] nfs4_lock_reclaim+0x60/0x8d [nfs]
>  [<ffffffffa02d57a3>] nfs4_do_reclaim+0x13d/0x322 [nfs]
>  [<ffffffffa02d5b21>] nfs4_run_state_manager+0x199/0x27f [nfs]
>  [<ffffffffa02d5988>] ? nfs4_run_state_manager+0x0/0x27f [nfs]
>  [<ffffffffa02d5988>] ? nfs4_run_state_manager+0x0/0x27f [nfs]
>  [<ffffffff8105e7bf>] kthread+0x5b/0x88
>  [<ffffffff81011dba>] child_rip+0xa/0x20
>  [<ffffffff8101177d>] ? restore_args+0x0/0x30
>  [<ffffffff8105e764>] ? kthread+0x0/0x88
>  [<ffffffff81011db0>] ? child_rip+0x0/0x20
> Code: 10 e1 49 8b 47 58 4d 8b af 90 00 00 00 be d0 00 00 00 bf 38 01
> 00 00 41 bc f4 ff ff ff 48 8b 80 a0 00 00 00 48 89 85 60 ff ff ff <49>
> 8b 45 10 4c 8b 70 38 49 8b 86 00 01 00 00 48 8b 80 a8 02 00
> RIP  [<ffffffffa02c8ff2>] _nfs4_do_setlk+0xe3/0x289 [nfs]
>  RSP <ffff880102361d30>
> CR2: 0000000000000010
> ---[ end trace 205a6f9494aa30de ]---
> 
> It's unclear to me whether I should blame this on the patches applied,
> or that this is just something never triggered unless the
> aforementioned bug is fixed...
> 
> - Rich

It is completely unrelated. The above appears to be due to a lock
recovery error after a server reboot. It has nothing to do with the mmap
writeback code.

Trond