[fuse-devel] Kernel oops in fuse_send_readpages()

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Hi,

I constantly get an oops while attempting to do parallel builds, using make
-j3, on a dualcore (Athlon X2) system. The filesystem in question is encfs
1.2.5, although it probably is a fuse-only problem, since it crashes inside
the kernel. The kernel is a vanilla 2.6.16.1, SMP, with both preemption and
BKL preemption turned off. The libfuse2 version is 2.5.2.

That oops does not happen when I do a non-parallel build, using just make
without -j. It also never happens when I try same parallel build on a non-SMP 
kernel. So it seems like an SMP-only problem.

The following is what gets into syslog:

> Mar 31 13:53:52 cactus kernel: fuse init (API version 7.6)
> Mar 31 13:55:21 cactus kernel: Unable to handle kernel NULL pointer dereference at virtual address 00000014
> Mar 31 13:55:21 cactus kernel:  printing eip:
> Mar 31 13:55:21 cactus kernel: f0afb856
> Mar 31 13:55:21 cactus kernel: *pde = 00000000
> Mar 31 13:55:21 cactus kernel: Oops: 0000 [#1]
> Mar 31 13:55:21 cactus kernel: SMP 
> Mar 31 13:55:21 cactus kernel: Modules linked in: fuse nfsd lockd sunrpc dm_mod thermal fan button ac battery ipt_REJECT xt_s
> tate ip_conntrack nfnetlink xt_tcpudp iptable_filter ip_tables x_tables cpufreq_ondemand powernow_k8 processor loop it87 hwmo
> n_vid eeprom i2c_isa usbhid usb_storage snd_emu10k1_synth snd_emux_synth snd_seq_virmidi snd_seq_midi_emul snd_seq_oss snd_se
> q_midi snd_seq_midi_event snd_seq snd_emu10k1 snd_rawmidi snd_ac97_codec snd_ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm snd_s
> eq_device snd_timer snd_page_alloc snd_util_mem i2c_nforce2 forcedeth emu10k1_gp snd_hwdep ehci_hcd gameport ohci_hcd usbcore
>  sata_nv snd libata
> Mar 31 13:55:21 cactus kernel: CPU:    1
> Mar 31 13:55:21 cactus kernel: EIP:    0060:[pg0+1080559702/1337472000]    Not tainted VLI
> Mar 31 13:55:21 cactus kernel: EFLAGS: 00010246   (2.6.16.1-i-np-nobkl #1) 
> Mar 31 13:55:21 cactus kernel: EIP is at fuse_send_readpages+0x1a/0x75 [fuse]
> Mar 31 13:55:21 cactus kernel: eax: 00000000   ebx: 00000000   ecx: e3828900   edx: eee83ec0
> Mar 31 13:55:21 cactus kernel: esi: 00000000   edi: e46464b8   ebp: eae99cc0   esp: e3815ce0
> Mar 31 13:55:21 cactus kernel: ds: 007b   es: 007b   ss: 0068
> Mar 31 13:55:21 cactus kernel: Process sh (pid: 5981, threadinfo=e3815000 task=efd04030)
> Mar 31 13:55:21 cactus kernel: Stack: <0>00000000 e3828900 eae99cc0 eee83ec0 f0afb921 e46464b8 eee83ec0 e3828900 
> Mar 31 13:55:21 cactus kernel:        b16587c0 00000007 e38289c0 00000007 b013819b eee83ec0 e38289c0 e3815d74 
> Mar 31 13:55:21 cactus kernel:        00000007 eee83ec0 e38289d0 00000006 00000007 e3815eac e3815ea8 e3815e80 
> Mar 31 13:55:21 cactus kernel: Call Trace:
> Mar 31 13:55:21 cactus kernel:  [pg0+1080559905/1337472000] fuse_readpages+0x70/0x7a [fuse]
> Mar 31 13:55:21 cactus kernel:  [__do_page_cache_readahead+289/481] __do_page_cache_readahead+0x121/0x1e1
> Mar 31 13:55:21 cactus kernel:  [blockable_page_cache_readahead+69/153] blockable_page_cache_readahead+0x45/0x99
> Mar 31 13:55:21 cactus kernel:  [current_fs_time+72/100] current_fs_time+0x48/0x64
> Mar 31 13:55:21 cactus kernel:  [blockable_page_cache_readahead+69/153] blockable_page_cache_readahead+0x45/0x99
> Mar 31 13:55:21 cactus kernel:  [page_cache_readahead+156/304] page_cache_readahead+0x9c/0x130
> Mar 31 13:55:21 cactus kernel:  [do_generic_mapping_read+319/1046] do_generic_mapping_read+0x13f/0x416
> Mar 31 13:55:21 cactus kernel:  [__generic_file_aio_read+365/440] __generic_file_aio_read+0x16d/0x1b8
> Mar 31 13:55:21 cactus kernel:  [file_read_actor+0/200] file_read_actor+0x0/0xc8
> Mar 31 13:55:21 cactus kernel:  [generic_file_read+173/195] generic_file_read+0xad/0xc3
> Mar 31 13:55:21 cactus kernel:  [pg0+1080556389/1337472000] fuse_finish_open+0x31/0x44 [fuse]
> Mar 31 13:55:21 cactus kernel:  [autoremove_wake_function+0/58] autoremove_wake_function+0x0/0x3a
> Mar 31 13:55:21 cactus kernel:  [sched_balance_self+537/612] sched_balance_self+0x219/0x264
> Mar 31 13:55:21 cactus kernel:  [vfs_read+135/283] vfs_read+0x87/0x11b
> Mar 31 13:55:21 cactus kernel:  [kernel_read+56/65] kernel_read+0x38/0x41
> Mar 31 13:55:21 cactus kernel:  [prepare_binprm+186/200] prepare_binprm+0xba/0xc8
> Mar 31 13:55:21 cactus kernel:  [do_execve+232/462] do_execve+0xe8/0x1ce
> Mar 31 13:55:21 cactus kernel:  [sys_execve+43/112] sys_execve+0x2b/0x70
> Mar 31 13:55:21 cactus kernel:  [syscall_call+7/11] syscall_call+0x7/0xb
> Mar 31 13:55:21 cactus kernel: Code: ff 59 89 f0 e8 d9 7a 63 bf 5a 5b 5e 5f 89 e8 5d c3 55 57 89 c7 8b 81 b4 00 00 00 56 31 f
> 6 53 8b a8 80 01 00 00 8b 87 b8 00 00 00 <8b> 58 14 8b 87 38 01 00 00 6a 0f 80 4f 74 04 c1 e0 0c 50 0f a4