[DRBD-user] Kernel oopses with DRBD

Adrian adrian at redforts.com
Wed Sep 2 17:42:24 CEST 2015

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hi Lars,

We continue to experience intermittent kernel warnings (oops) in kernel 
thread “drbd_w_db”. This occurs on servers having a DRBD resource in the 
primary role.

While we are currently unable to reproduce the issue in a controlled 
manner, we have mapped call traces to line numbers in the 4.1 kernel.org 
sources. This mapping is for kernels currently running on our production 
servers. Our kernel is compiled from the 4.1 kernel.org source code with 
the following lines defining default barrier options for ext3 and ext4 
file systems commented out:

fs/ext3/super.c: 1788
         // set_opt(sbi->s_mount_opt, BARRIER);

fs/ext4/super.c: 3578,3579
         // if ((def_mount_opts & EXT4_DEFM_NOBARRIER) == 0)
         //      set_opt(sb, BARRIER);

One observation after examining the source code is that the iov_iter 
interface code where the oops is triggered changed significantly between 
kernels 3.18 and 3.19 (a topic discussed here: 
https://lwn.net/Articles/625077/ ). Since DRBD is dependent upon 
networking code that calls this updated code, perhaps the changes are 
related to the issue we are experiencing with recent kernels.

Below I've included the following:

1) A drbd configuration file from one of our servers (i.e. “/etc/drbd.conf”)
2) For each 4.1 kernel oops, the oops report followed by matching source 
code line numbers.
3) A description of the process we used to map call stack addresses to 
kernel source line numbers.

Hopefully the line numbers will prove helpful when debugging this issue.

Regards,

Adrian

==========================================

1) DRBD CONFIGURATION

--------/etc/drbd.conf--------

# You can find an example in /usr/share/doc/drbd.../drbd.conf.example

# include "drbd.d/global_common.conf";
# include "drbd.d/*.res";

global {
     usage-count no;
}

common {
     net { protocol A; }
     syncer { rate 100M; }
}

resource db {
     disk { on-io-error detach; }
     on uk3 {
         device /dev/drbd0;
         disk /dev/xvdd;
         address 192.168.133.115:7791;
         meta-disk internal;
     }
     on uk4 {
         device /dev/drbd0;
         disk /dev/xvdd;
         address 192.168.133.117:7791;
         meta-disk internal;
     }
}

========================================================================

2) KERNEL OOPS INFORMATION - For Each: Error log followed by line numbers

KERNEL OOPS 1 - ERROR LOG - Version 4.1.0 with barrier patch - 
2015-07-08 18:11:09

uk3 kern.alert kernel BUG: unable to handle kernel paging request at 
0000000000001000
uk3 kern.alert kernel IP: [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel PGD 77b46067 PUD 6f0df067 PMD 0
uk3 kern.warning kernel Oops: 0000 [#1] SMP
uk3 kern.warning kernel Modules linked in:
uk3 kern.warning kernel CPU: 0 PID: 4516 Comm: drbd_w_db Not tainted 
4.1.0-x86_64-linode59 #1
uk3 kern.warning kernel Hardware name: QEMU Standard PC (i440FX + PIIX, 
1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 
04/01/2014
uk3 kern.warning kernel task: ffff88006f024a40 ti: ffff8800793b0000 
task.ti: ffff8800793b0000
uk3 kern.warning kernel RIP: 0010:[<ffffffff8158ba60>] 
[<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP: 0018:ffff8800793b3b60  EFLAGS: 00010292
uk3 kern.warning kernel RAX: 0000000000000028 RBX: 0000000000000028 RCX: 
0000000000000028
uk3 kern.warning kernel RDX: ffff8800793b3c90 RSI: 0000000000001000 RDI: 
ffff8800384eae98
uk3 kern.warning kernel RBP: ffff8800793b3c80 R08: 0000000000000000 R09: 
ffff8800384eaec0
uk3 kern.warning kernel R10: ffff8800384eae98 R11: 000000000000bab2 R12: 
00000000000005f0
uk3 kern.warning kernel R13: ffff880068334800 R14: 00000000000005f0 R15: 
ffff8800716e3640
uk3 kern.warning kernel FS:  0000000000000000(0000) 
GS:ffff88007fc00000(0000) knlGS:0000000000000000
uk3 kern.warning kernel CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
uk3 kern.warning kernel CR2: 0000000000001000 CR3: 00000000760ef000 CR4: 
00000000001407f0
uk3 kern.warning kernel Stack:
uk3 kern.warning kernel 00000000000005f0 ffff880073f43200 
00000000000005f0 ffff8800793b3c70
uk3 kern.warning kernel 0000000000000000 ffff880068334800 
00000000000005f0 ffff8800716e3640
uk3 kern.warning kernel ffffffff81838006 000040000000f428 
ffff8800793b3c80 0000000000000000
uk3 kern.warning kernel Call Trace:
uk3 kern.warning kernel [<ffffffff81838006>] ? tcp_sendmsg+0x3ee/0x9b4
uk3 kern.warning kernel [<ffffffff8175c6de>] ? sock_sendmsg+0x2e/0x3b
uk3 kern.warning kernel [<ffffffff81666c4a>] ? drbd_send+0xa5/0x171
uk3 kern.warning kernel [<ffffffff81666d24>] ? drbd_send_all+0xe/0x23
uk3 kern.warning kernel [<ffffffff816682a5>] ? _drbd_no_send_page+0x47/0x5d
uk3 kern.warning kernel [<ffffffff8166887d>] ? drbd_send_dblock+0x2e1/0x4ab
uk3 kern.warning kernel [<ffffffff811075ae>] ? __wake_up_common+0x47/0x7d
uk3 kern.warning kernel [<ffffffff81107a84>] ? __wake_up+0x3a/0x4b
uk3 kern.warning kernel [<ffffffff81651643>] ? w_send_dblock+0xd3/0x139
uk3 kern.warning kernel [<ffffffff8165279e>] ? drbd_worker+0x124/0x302
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff81665fa2>] ? drbd_thread_setup+0x47/0x10c
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff810f088c>] ? kthread+0xca/0xd2
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel [<ffffffff81962362>] ? ret_from_fork+0x42/0x70
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 
48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 
29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 
08 75 05
uk3 kern.alert kernel RIP  [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP <ffff8800793b3b60>
uk3 kern.warning kernel CR2: 0000000000001000
uk3 kern.warning kernel ---[ end trace e217b95518b37926 ]---

KERNEL OOPS 1 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-07-08 18:11:09

ffffffff8158ba60:copy_from_iter lib/iov_iter.c:416
**********inline:skb_do_copy_data_nocache include/net/sock.h:1791
**********inline:skb_add_data_no_cache include/net/sock.h:1802
ffffffff81838006:tcp_sendmsg net/ipv4/tcp.c:1177
**********inline:sock_sendmsg_nosec net/socket.c:613 (***addr2line 
reports 614)
ffffffff8175c6de:sock_sendmsg net/socket.c:623
ffffffff81666c4a:drbd_send drivers/block/drbd/drbd_main.c:1805 
(***addr2line reports 1806)
ffffffff81666d24:drbd_send_all drivers/block/drbd/drbd_main.c:1849 
(***addr2line reports 1850)
ffffffff816682a5:_drbd_no_send_page drivers/block/drbd/drbd_main.c:1492 
(***addr2line reports 1494)
ffffffff8166887d:drbd_send_dblock /drivers/block/drbd/drbd_main.c:1678
ffffffff811075ae:__wake_up_common kernel/sched/wait.c:73
ffffffff81107a84:__wake_up kernel/sched/wait.c:95 (***addr2line reports 97)
ffffffff81651643:w_send_dblock drivers/block/drbd/drbd_worker.c:1404 
(***addr2line reports 1405)

*** Developer analysis of call stack stopped here ***
ffffffff8165279e:drbd_worker drivers/block/drbd/drbd_worker.c:2122
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff81665fa2:drbd_thread_setup drivers/block/drbd/drbd_main.c:337
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff810f088c:kthread kernel/kthread.c:210
ffffffff810f07c2:kthread kernel/kthread.c:176
ffffffff81962362:ret_from_fork arch/x86/kernel/entry_64.S:640
ffffffff810f07c2:kthread kernel/kthread.c:176

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

KERNEL OOPS 2 - ERROR LOG - Version 4.1.0 with barrier patch - 
2015-07-27 07:44:17

uk3 kern.alert kernel BUG: unable to handle kernel NULL pointer 
dereference at 0000000000000003
uk3 kern.alert kernel IP: [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel PGD 759b0067 PUD 759b1067 PMD 0
uk3 kern.warning kernel Oops: 0000 [#1] SMP
uk3 kern.warning kernel Modules linked in:
uk3 kern.warning kernel CPU: 0 PID: 4448 Comm: drbd_w_db Not tainted 
4.1.0-x86_64-linode59 #1
uk3 kern.warning kernel Hardware name: QEMU Standard PC (i440FX + PIIX, 
1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 
04/01/2014
uk3 kern.warning kernel task: ffff880075a87380 ti: ffff880075a68000 
task.ti: ffff880075a68000
uk3 kern.warning kernel RIP: 0010:[<ffffffff8158ba60>] 
[<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP: 0018:ffff880075a6bb60  EFLAGS: 00010282
uk3 kern.warning kernel RAX: 00000000000005f0 RBX: 00000000000005f0 RCX: 
00000000000005f0
uk3 kern.warning kernel RDX: ffff880075a6bc80 RSI: 0000000000000003 RDI: 
ffff88006c9e8aa8
uk3 kern.warning kernel RBP: ffff880075a6bc80 R08: 0000000000000190 R09: 
ffff88006c9e9098
uk3 kern.warning kernel R10: ffff88006c9e8aa8 R11: 00000000000005a8 R12: 
0000000000000a10
uk3 kern.warning kernel R13: ffff8800788fd000 R14: ffff880075a87b40 R15: 
ffff88007bae3e00
uk3 kern.warning kernel FS:  0000000000000000(0000) 
GS:ffff88007fc00000(0000) knlGS:0000000000000000
uk3 kern.warning kernel CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
uk3 kern.warning kernel CR2: 0000000000000003 CR3: 000000007597a000 CR4: 
00000000001407f0
uk3 kern.warning kernel Stack:
uk3 kern.warning kernel 00000000000005f0 ffff8800788fca00 
0000000000000a10 ffff880075a6bc70
uk3 kern.warning kernel 00000000000005f0 ffff8800788fd000 
ffff880075a87b40 ffff88007bae3e00
uk3 kern.warning kernel ffffffff81838225 000040000000f6e0 
ffff880075a6bc80 0000000000000a10
uk3 kern.warning kernel Call Trace:
uk3 kern.warning kernel [<ffffffff81838225>] ? tcp_sendmsg+0x60d/0x9b4
uk3 kern.warning kernel [<ffffffff8175c6de>] ? sock_sendmsg+0x2e/0x3b
uk3 kern.warning kernel [<ffffffff81666c4a>] ? drbd_send+0xa5/0x171
uk3 kern.warning kernel [<ffffffff81666d24>] ? drbd_send_all+0xe/0x23
uk3 kern.warning kernel [<ffffffff816682a5>] ? _drbd_no_send_page+0x47/0x5d
uk3 kern.warning kernel [<ffffffff8166887d>] ? drbd_send_dblock+0x2e1/0x4ab
uk3 kern.warning kernel [<ffffffff81107a84>] ? __wake_up+0x3a/0x4b
uk3 kern.warning kernel [<ffffffff81651643>] ? w_send_dblock+0xd3/0x139
uk3 kern.warning kernel [<ffffffff8165279e>] ? drbd_worker+0x124/0x302
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff81665fa2>] ? drbd_thread_setup+0x47/0x10c
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff810f088c>] ? kthread+0xca/0xd2
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel [<ffffffff81962362>] ? ret_from_fork+0x42/0x70
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 
48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 
29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 
08 75 05
uk3 kern.alert kernel RIP  [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP <ffff880075a6bb60>
uk3 kern.warning kernel CR2: 0000000000000003
uk3 kern.warning kernel ---[ end trace 72c4b2b13ae06bb9 ]---

KERNEL OOPS 2 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-07-27 07:44:17

ffffffff8158ba60:copy_from_iter lib/iov_iter.c:416
**********inline:skb_do_copy_data_nocache include/net/sock.h:1791
**********inline:skb_copy_to_page_nocache include/net/sock.h:1817
ffffffff81838225:tcp_sendmsg net/ipv4/tcp.c:1202
**********inline:sock_sendmsg_nosec net/socket.c:613 (***addr2line 
reports 614)
ffffffff8175c6de:sock_sendmsg net/socket.c:623
ffffffff81666c4a:drbd_send drivers/block/drbd/drbd_main.c:1805: 
(***addr2line reports 1806)
ffffffff81666d24:drbd_send_all drivers/block/drbd/drbd_main.c:1849 
(***addr2line reports 1850)
ffffffff816682a5:_drbd_no_send_page drivers/block/drbd/drbd_main.c:1492 
(***addr2line reports 1494)
**********inline:_drbd_send_bio drivers/block/drbd/drbd_main.c:1557 
(***addr2line reports 1561)
ffffffff8166887d:drbd_send_dblock drivers/block/drbd/drbd_main.c:1678

**** Developer analysis of call stack stopped here ****
ffffffff81107a84:__wake_up kernel/sched/wait.c:97
**********inline:req_mod drivers/block/drbd/drbd_req.h:320
ffffffff81651643:w_send_dblock drivers/block/drbd/drbd_worker.c:1405
ffffffff8165279e:drbd_worker drivers/block/drbd/drbd_worker.c:2122
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff81665fa2:drbd_thread_setup drivers/block/drbd/drbd_main.c:337
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff810f088c:kthread kernel/kthread.c:210
ffffffff810f07c2:kthread kernel/kthread.c:176
ffffffff81962362:ret_from_fork arch/x86/kernel/entry_64.S:640
ffffffff810f07c2:kthread kernel/kthread.c:176

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

KERNEL OOPS 3 - ERROR LOG - Version 4.1.0 with barrier patch - 
2015-07-27 18:04:49

uk4 kern.alert kernel BUG: unable to handle kernel NULL pointer 
dereference at 0000000000000003
uk4 kern.alert kernel IP: [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel PGD 77e8d067 PUD 78b0c067 PMD 0
uk4 kern.warning kernel Oops: 0000 [#1] SMP
uk4 kern.warning kernel Modules linked in:
uk4 kern.warning kernel CPU: 0 PID: 4166 Comm: drbd_w_db Not tainted 
4.1.0-x86_64-linode59 #1
uk4 kern.warning kernel Hardware name: QEMU Standard PC (i440FX + PIIX, 
1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 
04/01/2014
uk4 kern.warning kernel task: ffff8800741498c0 ti: ffff88007b7f0000 
task.ti: ffff88007b7f0000
uk4 kern.warning kernel RIP: 0010:[<ffffffff8158ba60>] 
[<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel RSP: 0018:ffff88007b7f3b60  EFLAGS: 00010282
uk4 kern.warning kernel RAX: 00000000000005f0 RBX: 00000000000005f0 RCX: 
00000000000005f0
uk4 kern.warning kernel RDX: ffff88007b7f3c80 RSI: 0000000000000003 RDI: 
ffff880002af9be0
uk4 kern.warning kernel RBP: ffff88007b7f3c80 R08: 00000000000003f0 R09: 
ffff880002afa1d0
uk4 kern.warning kernel R10: ffff880002af9be0 R11: 00000000000005a8 R12: 
0000000000000a10
uk4 kern.warning kernel R13: ffff88006a7d8e00 R14: ffff88007414a080 R15: 
ffff880077421f00
uk4 kern.warning kernel FS:  0000000000000000(0000) 
GS:ffff88007fc00000(0000) knlGS:0000000000000000
uk4 kern.warning kernel CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
uk4 kern.warning kernel CR2: 0000000000000003 CR3: 0000000077e8c000 CR4: 
00000000001407f0
uk4 kern.warning kernel Stack:
uk4 kern.warning kernel 00000000000005f0 ffff88006a7d9e00 
0000000000000a10 ffff88007b7f3c70
uk4 kern.warning kernel 00000000000005f0 ffff88006a7d8e00 
ffff88007414a080 ffff880077421f00
uk4 kern.warning kernel ffffffff81838225 000040000000f480 
ffff88007b7f3c80 0000000000000a10
uk4 kern.warning kernel Call Trace:
uk4 kern.warning kernel [<ffffffff81838225>] ? tcp_sendmsg+0x60d/0x9b4
uk4 kern.warning kernel [<ffffffff8175c6de>] ? sock_sendmsg+0x2e/0x3b
uk4 kern.warning kernel [<ffffffff81666c4a>] ? drbd_send+0xa5/0x171
uk4 kern.warning kernel [<ffffffff81666d24>] ? drbd_send_all+0xe/0x23
uk4 kern.warning kernel [<ffffffff816682a5>] ? _drbd_no_send_page+0x47/0x5d
uk4 kern.warning kernel [<ffffffff8166887d>] ? drbd_send_dblock+0x2e1/0x4ab
uk4 kern.warning kernel [<ffffffff81107a84>] ? __wake_up+0x3a/0x4b
uk4 kern.warning kernel [<ffffffff81651643>] ? w_send_dblock+0xd3/0x139
uk4 kern.warning kernel [<ffffffff8165279e>] ? drbd_worker+0x124/0x302
uk4 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk4 kern.warning kernel [<ffffffff81665fa2>] ? drbd_thread_setup+0x47/0x10c
uk4 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk4 kern.warning kernel [<ffffffff810f088c>] ? kthread+0xca/0xd2
uk4 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk4 kern.warning kernel [<ffffffff81962362>] ? ret_from_fork+0x42/0x70
uk4 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk4 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 
48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 
29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 
08 75 05
uk4 kern.alert kernel RIP  [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel RSP <ffff88007b7f3b60>
uk4 kern.warning kernel CR2: 0000000000000003
uk4 kern.warning kernel ---[ end trace 1277a4d533113ace ]---

KERNEL OOPS 3 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-07-27 18:04:49

ffffffff8158ba60:copy_from_iter lib/iov_iter.c:416
**********inline:skb_do_copy_data_nocache include/net/sock.h:1791
**********inline:skb_copy_to_page_nocache include/net/sock.h:1817
ffffffff81838225:tcp_sendmsg net/ipv4/tcp.c:1202
**********inline:sock_sendmsg_nosec net/socket.c:613 (***addr2line 
reports 614)
ffffffff8175c6de:sock_sendmsg net/socket.c:623
ffffffff81666c4a:drbd_send drivers/block/drbd/drbd_main.c:1805 
(***addr2line reports 1806)
ffffffff81666d24:drbd_send_all drivers/block/drbd/drbd_main.c:1849 
(***addr2line reports 1850)
ffffffff816682a5:_drbd_no_send_page drivers/block/drbd/drbd_main.c:1492 
(***addr2line reports 1494)
**********inline:_drbd_send_bio drivers/block/drbd/drbd_main.c:1557 
(***addr2line reports 1561)
ffffffff8166887d:drbd_send_dblock drivers/block/drbd/drbd_main.c:1678

**** Developer analysis of call stack stopped here ****
ffffffff81107a84:__wake_up kernel/sched/wait.c:97
**********inline:req_mod drivers/block/drbd/drbd_req.h:320
ffffffff81651643:w_send_dblock drivers/block/drbd/drbd_worker.c:1405
ffffffff8165279e:drbd_worker drivers/block/drbd/drbd_worker.c:2122
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff81665fa2:drbd_thread_setup drivers/block/drbd/drbd_main.c:337
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff810f088c:kthread kernel/kthread.c:210
ffffffff810f07c2:kthread kernel/kthread.c:176
ffffffff81962362:ret_from_fork arch/x86/kernel/entry_64.S:640
ffffffff810f07c2:kthread kernel/kthread.c:176

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

KERNEL OOPS 4 - ERROR LOG - Version 4.1.0 with barrier patch - 
2015-08-13 16:39:28

uk3 kern.alert kernel BUG: unable to handle kernel paging request at 
0000000000001000
uk3 kern.alert kernel IP: [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel PGD 0
uk3 kern.warning kernel Oops: 0000 [#1] SMP
uk3 kern.warning kernel Modules linked in:
uk3 kern.warning kernel CPU: 0 PID: 6121 Comm: drbd_w_db Not tainted 
4.1.0-x86_64-linode59 #1
uk3 kern.warning kernel task: ffff88007c0d3180 ti: ffff8800776b8000 
task.ti: ffff8800776b8000
uk3 kern.warning kernel RIP: e030:[<ffffffff8158ba60>] 
[<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP: e02b:ffff8800776bbb60  EFLAGS: 00010282
uk3 kern.warning kernel RAX: 00000000000004e0 RBX: 00000000000004e0 RCX: 
00000000000004e0
uk3 kern.warning kernel RDX: ffff8800776bbc90 RSI: 0000000000001000 RDI: 
ffff880077acd9e0
uk3 kern.warning kernel RBP: ffff8800776bbc80 R08: 0000000000000000 R09: 
ffff880077acdec0
uk3 kern.warning kernel R10: ffff880077acd9e0 R11: 00000000000005a8 R12: 
00000000000005f0
uk3 kern.warning kernel R13: ffff88007c74de00 R14: 00000000000005f0 R15: 
ffff880000ed5540
uk3 kern.warning kernel FS:  0000000000000000(0000) 
GS:ffff88007d200000(0000) knlGS:ffff88007d200000
uk3 kern.warning kernel CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
uk3 kern.warning kernel CR2: 0000000000001000 CR3: 00000000771b3000 CR4: 
0000000000042660
uk3 kern.warning kernel Stack:
uk3 kern.warning kernel 00000000000005f0 ffff880077211000 
00000000000005f0 ffff8800776bbc70
uk3 kern.warning kernel 0000000000000000 ffff88007c74de00 
00000000000005f0 ffff880000ed5540
uk3 kern.warning kernel ffffffff81838006 000040000000ef70 
ffff8800776bbc80 0000000000000000
uk3 kern.warning kernel Call Trace:
uk3 kern.warning kernel [<ffffffff81838006>] ? tcp_sendmsg+0x3ee/0x9b4
uk3 kern.warning kernel [<ffffffff8175c6de>] ? sock_sendmsg+0x2e/0x3b
uk3 kern.warning kernel [<ffffffff81666c4a>] ? drbd_send+0xa5/0x171
uk3 kern.warning kernel [<ffffffff81666d24>] ? drbd_send_all+0xe/0x23
uk3 kern.warning kernel [<ffffffff816682a5>] ? _drbd_no_send_page+0x47/0x5d
uk3 kern.warning kernel [<ffffffff8166887d>] ? drbd_send_dblock+0x2e1/0x4ab
uk3 kern.warning kernel [<ffffffff811075ae>] ? __wake_up_common+0x47/0x7d
uk3 kern.warning kernel [<ffffffff81107a84>] ? __wake_up+0x3a/0x4b
uk3 kern.warning kernel [<ffffffff81651643>] ? w_send_dblock+0xd3/0x139
uk3 kern.warning kernel [<ffffffff8165279e>] ? drbd_worker+0x124/0x302
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff81665fa2>] ? drbd_thread_setup+0x47/0x10c
uk3 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk3 kern.warning kernel [<ffffffff810f088c>] ? kthread+0xca/0xd2
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel [<ffffffff81962362>] ? ret_from_fork+0x42/0x70
uk3 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk3 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 
48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 
29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 
08 75 05
uk3 kern.alert kernel RIP  [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk3 kern.warning kernel RSP <ffff8800776bbb60>
uk3 kern.warning kernel CR2: 0000000000001000
uk3 kern.warning kernel ---[ end trace edb6ef1729c2cd08 ]---

KERNEL OOPS 4 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-08-13 16:39:28

ffffffff8158ba60:copy_from_iter lib/iov_iter.c:416
**********inline:skb_do_copy_data_nocache include/net/sock.h:1791
**********inline:skb_add_data_nocache include/net/sock.h:1802
ffffffff81838006:tcp_sendmsg net/ipv4/tcp.c:1177
**********inline:sock_sendmsg_nosec net/socket.c:613 (***addr2line 
reports 614)
ffffffff8175c6de:sock_sendmsg net/socket.c:623
ffffffff81666c4a:drbd_send drivers/block/drbd/drbd_main.c:1806 
(***addr2line reports 1806)
ffffffff81666d24:drbd_send_all drivers/block/drbd/drbd_main.c:1849 
(***addr2line reports 1850)
ffffffff816682a5:_drbd_no_send_page drivers/block/drbd/drbd_main.c:1492 
(***addr2line reports 1494)
**********inline:_drbd_send_bio drivers/block/drbd/drbd_main.c:1557 
(***addr2line reports 1561)
ffffffff8166887d:drbd_send_dblock drivers/block/drbd/drbd_main.c:1678

*** Developer analysis of call stack stopped here ***
ffffffff811075ae:__wake_up_common kernel/sched/wait.c:73
ffffffff81107a84:__wake_up kernel/sched/wait.c:97
**********inline:req_mod drivers/block/drbd/drbd_req.h:320
ffffffff81651643:w_send_dblock:drivers/block/drbd/drbd_worker.c:1405
ffffffff8165279e:drbd_worker drivers/block/drbd/drbd_worker.c:2122
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff81665fa2:drbd_thread_setup drivers/block/drbd/drbd_main.c:337
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff810f088c:kthread kernel/kthread.c:210
ffffffff810f07c2:kthread kernel/kthread.c:176
ffffffff81962362:ret_from_fork arch/x86/kernel/entry_64.S:640
ffffffff810f07c2:kthread kernel/kthread.c:176

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

KERNEL OOPS 5 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-08-28 15:58:21

uk4 kern.alert kernel IP: [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel PGD 76f43067 PUD 76d64067 PMD 0
uk4 kern.warning kernel Oops: 0000 [#1] SMP
uk4 kern.warning kernel Modules linked in:
uk4 kern.warning kernel CPU: 0 PID: 3967 Comm: drbd_w_db Not tainted 
4.1.0-x86_64-linode59 #1
uk4 kern.warning kernel task: ffff88007c0b39c0 ti: ffff8800776a4000 
task.ti: ffff8800776a4000
uk4 kern.warning kernel RIP: e030:[<ffffffff8158ba60>] 
[<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel RSP: e02b:ffff8800776a7b60 EFLAGS: 00010286
uk4 kern.warning kernel RAX: 00000000000005f0 RBX: 00000000000005f0 RCX: 
00000000000005f0
uk4 kern.warning kernel RDX: ffff8800776a7c80 RSI: 0000000000000003 RDI: 
ffff880013a30c30
uk4 kern.warning kernel RBP: ffff8800776a7c80 R08: 00000000000000d8 R09: 
ffff880013a31220
uk4 kern.warning kernel R10: ffff880013a30c30 R11: 000000000000bc4a R12: 
0000000000000a10
uk4 kern.warning kernel R13: ffff8800023fc000 R14: ffff88007c0b4180 R15: 
ffff8800358df440
uk4 kern.warning kernel FS: 0000000000000000(0000) 
GS:ffff88007d200000(0000) knlGS:ffff88007d200000
uk4 kern.warning kernel CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033
uk4 kern.warning kernel CR2: 0000000000000003 CR3: 000000007802f000 CR4: 
0000000000042660
uk4 kern.warning kernel Stack:
uk4 kern.warning kernel 00000000000005f0 ffff880074ad4c00 
0000000000000a10 ffff8800776a7c70
uk4 kern.warning kernel 00000000000005f0 ffff8800023fc000 
ffff88007c0b4180 ffff8800358df440
uk4 kern.warning kernel ffffffff81838225 0000000000000000 
ffff8800776a7c80 0000000000000a10
uk4 kern.warning kernel Call Trace:
uk4 kern.warning kernel [<ffffffff81838225>] ? tcp_sendmsg+0x60d/0x9b4
uk4 kern.warning kernel [<ffffffff8175c6de>] ? sock_sendmsg+0x2e/0x3b
uk4 kern.warning kernel [<ffffffff81666c4a>] ? drbd_send+0xa5/0x171
uk4 kern.warning kernel [<ffffffff81666d24>] ? drbd_send_all+0xe/0x23
uk4 kern.warning kernel [<ffffffff816682a5>] ? _drbd_no_send_page+0x47/0x5d
uk4 kern.warning kernel [<ffffffff8166887d>] ? drbd_send_dblock+0x2e1/0x4ab
uk4 kern.warning kernel [<ffffffff8165f050>] ? mod_rq_state+0x463/0x4e1
uk4 kern.warning kernel [<ffffffff81961b39>] ? _raw_spin_lock_irq+0xc/0x65
uk4 kern.warning kernel [<ffffffff81651643>] ? w_send_dblock+0xd3/0x139
uk4 kern.warning kernel [<ffffffff8165279e>] ? drbd_worker+0x124/0x302
uk4 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk4 kern.warning kernel [<ffffffff81665fa2>] ? drbd_thread_setup+0x47/0x10c
uk4 kern.warning kernel [<ffffffff81665f5b>] ? w_complete+0x13/0x13
uk4 kern.warning kernel [<ffffffff810f088c>] ? kthread+0xca/0xd2
uk4 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk4 kern.warning kernel [<ffffffff81962362>] ? ret_from_fork+0x42/0x70
uk4 kern.warning kernel [<ffffffff810f07c2>] ? 
kthread_freezable_should_stop+0x40/0x40
uk4 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 
48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 
29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 
08 75 05
uk4 kern.alert kernel RIP [<ffffffff8158ba60>] copy_from_iter+0x140/0x24e
uk4 kern.warning kernel RSP <ffff8800776a7b60>
uk4 kern.warning kernel CR2: 0000000000000003
uk4 kern.warning kernel ---[ end trace 44570100730370c8 ]---

KERNEL OOPS 5 - LINE NUMBERS - Version 4.1.0 with barrier patch - 
2015-08-28 15:58:21

ffffffff8158ba60:copy_from_iter lib/iov_iter.c:416
**********inline:skb_do_copy_data_nocache include/net/sock.h:1791
**********inline:skb_copy_to_page_nocache include/net/sock.h:1817
ffffffff81838225:tcp_sendmsg net/ipv4/tcp.c:1202
**********inline:sock_sendmsg_nosec net/socket.c:613 (***addr2line 
reports 614)
ffffffff8175c6de:sock_sendmsg net/socket.c:623
ffffffff81666c4a:drbd_send drivers/block/drbd/drbd_main.c:1805 
(***addr2line reports 1806)
ffffffff81666d24:drbd_send_all drivers/block/drbd/drbd_main.c:1849 
(***addr2line reports 1850)
ffffffff816682a5:_drbd_no_send_page drivers/block/drbd/drbd_main.c:1492 
(***addr2line reports 1494)
**********inline:_drbd_send_bio drivers/block/drbd/drbd_main.c:1557 
(***addr2line reports 1561)
ffffffff8166887d:drbd_send_dblock drivers/block/drbd/drbd_main.c:1678

*** Developer analysis of call stack stopped here ***
ffffffff8165f050:mod_rq_state drivers/block/drbd/drbd_req.c:533
**********inline:do_raw_spin_lock ./arch/x86/include/asm/spinlock.h:106
**********inline:__raw_spin_lock_irq include/linux/spinlock_api_smp.h:131
ffffffff81961b39:_raw_spin_lock_irq kernel/locking/spinlock.c:167
**********inline:req_mod drivers/block/drbd/drbd_req.h:320
ffffffff81651643:w_send_dblock drivers/block/drbd/drbd_worker.c:1405
ffffffff8165279e:drbd_worker drivers/block/drbd/drbd_worker.c:2122
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff81665fa2:drbd_thread_setup drivers/block/drbd/drbd_main.c:337
ffffffff81665f5b:drbd_thread_setup drivers/block/drbd/drbd_main.c:324
ffffffff810f088c:kthread kernel/kthread.c:210
ffffffff810f07c2:kthread kernel/kthread.c:176
ffffffff81962362:ret_from_fork arch/x86/kernel/entry_64.S:640
ffffffff810f07c2:kthread kernel/kthread.c:176

=============================================================================

3) MAPPING PROCESS - Call Stack Addresses To Kernel Source Line Numbers:

- Download 4.1 kernel sources from kernel.org.
- Modify source code as described above (i.e. commenting out barrier 
related lines)
- Obtain a “.config” file from a live server “zcat /proc/config.gz”.
- Obtain compiler version “cat /proc/version” which identifies “gcc 
version 4.7.2 (Debian 4.7.2-5)”
- Build kernel with matching compiler on dual core Debian 7 (Wheezy) 
system:  “make -j3 deb-pkg”
- Compare Symbol.map file with one obtained from live server via “cat 
/proc/kallsyms” to assure function addresses match.
- Extract kernel sources again and run “menuconfig” to update .config as 
follows:
< # CONFIG_DEBUG_INFO is not set
---
 > CONFIG_DEBUG_INFO=y
 > CONFIG_DEBUG_INFO_REDUCED=y
 > CONFIG_DEBUG_INFO_SPLIT=y
 > CONFIG_DEBUG_INFO_DWARF4=y
 > CONFIG_GDB_SCRIPTS=y
- Build a matching debug version of the kernel: “make -j3 deb-pkg”
- Compare Symbol.map file with one obtained from live server via “cat 
/proc/kallsyms” to assure function addresses match.

At this point, the command “addr2line -fie ./vmlinux <address>” is used 
to map each address reported in the Oops call trace to one or more lines 
in the kernel source. Minor adjustments are made to the lines 
reported by “addr2line” as they often fall just after a function call in 
the code. Finally inline function calls reported by “addr2line” are 
manually inserted into the call trace to clarify the lines of code 
called that lead to the Oops.



On 08/18/2015 06:40 PM, Lars Ellenberg wrote:
> On Fri, Aug 14, 2015 at 12:32:48PM +0200, Ben Siemerink wrote:
>> Hello,
>>
>>
>> Lately we have experienced five kernel oopses in our DRBD setup. The
>> stack trace is very similar every time.
>>
>> If you need more information, please let me know. Thank you in advance.
>>
>>
>> Kind regards,
>> Ben.
>>
>> ----------
>>
>> 2015-05-05T09:31:02.759829+00:00 uk3 kern.info kernel Linux version 4.0.1-x86_64-linode55 (maker at build) (gcc version 4.7.2 (Debian 4.7.2-5) ) #3 SMP Wed Apr 29 11:10:11 EDT 2015
>> 2015-05-05T09:31:02.760314+00:00 uk3 kern.info kernel drbd: initialized. Version: 8.4.5 (api:1/proto:86-101)
> reproduce with kernel.org kernel, and resolve the symbols to line numbers.
> preferably even reproduce with drbd 8.4 from git,
> and still resolve line numbers.
>
>> 2015-05-13T14:14:58.163337+00:00 uk3 kern.alert kernel BUG: unable to handle kernel NULL pointer dereference at 0000000000000003
>> 2015-05-13T14:14:58.163365+00:00 uk3 kern.alert kernel IP: [<ffffffff8157804f>] copy_from_iter+0x140/0x24e
>> 2015-05-13T14:14:58.163369+00:00 uk3 kern.warning kernel PGD 759f7067 PUD 77777067 PMD 0
>> 2015-05-13T14:14:58.163372+00:00 uk3 kern.warning kernel Oops: 0000 [#1] SMP
>> 2015-05-13T14:14:58.163374+00:00 uk3 kern.warning kernel Modules linked in:
>> 2015-05-13T14:14:58.163390+00:00 uk3 kern.warning kernel CPU: 0 PID: 3606 Comm: drbd_w_db Not tainted 4.0.1-x86_64-linode55 #3
>> 2015-05-13T14:14:58.163392+00:00 uk3 kern.warning kernel task: ffff88007c5071c0 ti: ffff880075bd0000 task.ti: ffff880075bd0000
>> 2015-05-13T14:14:58.163395+00:00 uk3 kern.warning kernel RIP: e030:[<ffffffff8157804f>]  [<ffffffff8157804f>] copy_from_iter+0x140/0x24e
>> 2015-05-13T14:14:58.163397+00:00 uk3 kern.warning kernel RSP: e02b:ffff880075bd3ae0  EFLAGS: 00010286
>> 2015-05-13T14:14:58.163399+00:00 uk3 kern.warning kernel RAX: 0000000000000440 RBX: 0000000000000440 RCX: 0000000000000440
>> 2015-05-13T14:14:58.163401+00:00 uk3 kern.warning kernel RDX: ffff880075bd3c88 RSI: 0000000000000003 RDI: ffff880005f25088
>> 2015-05-13T14:14:58.163403+00:00 uk3 kern.warning kernel RBP: ffff880075bd3c88 R08: 0000000000000000 R09: ffff880005f254c8
>> 2015-05-13T14:14:58.163409+00:00 uk3 kern.warning kernel R10: ffff880005f25088 R11: ffff88007d2149c0 R12: 0000000000000a10
>> 2015-05-13T14:14:58.163411+00:00 uk3 kern.warning kernel R13: ffff8800720f3000 R14: ffff88007c507978 R15: ffff880075ab57c0
>> 2015-05-13T14:14:58.163413+00:00 uk3 kern.warning kernel FS:  0000000000000000(0000) GS:ffff88007d200000(0000) knlGS:ffff880179b40000
>> 2015-05-13T14:14:58.163415+00:00 uk3 kern.warning kernel CS:  e033 DS: 0000 ES: 0000 CR0: 0000000080050033
>> 2015-05-13T14:14:58.163417+00:00 uk3 kern.warning kernel CR2: 0000000000000003 CR3: 00000000771e1000 CR4: 0000000000042660
>> 2015-05-13T14:14:58.163419+00:00 uk3 kern.warning kernel Stack:
>> 2015-05-13T14:14:58.163421+00:00 uk3 kern.warning kernel 00000000000005f0 ffff88002d75f200 0000000000000a10 ffff880075bd3c78
>> 2015-05-13T14:14:58.163422+00:00 uk3 kern.warning kernel 00000000000005f0 ffff8800720f3000 ffff88007c507978 ffff880075ab57c0
>> 2015-05-13T14:14:58.163429+00:00 uk3 kern.warning kernel ffffffff817d0f76 000040000000fa20 ffff880075bd3c88 0000000000000a10
>> 2015-05-13T14:14:58.163430+00:00 uk3 kern.warning kernel Call Trace:
>> 2015-05-13T14:14:58.163432+00:00 uk3 kern.warning kernel [<ffffffff817d0f76>] ? tcp_sendmsg+0x610/0x9b7
>> 2015-05-13T14:14:58.163434+00:00 uk3 kern.warning kernel [<ffffffff816f8787>] ? sock_sendmsg+0x59/0x73
>> 2015-05-13T14:14:58.163436+00:00 uk3 kern.warning kernel [<ffffffff816f87ee>] ? kernel_sendmsg+0x4d/0x5d
>> 2015-05-13T14:14:58.163441+00:00 uk3 kern.warning kernel [<ffffffff81645a3f>] ? drbd_send+0xa2/0x16d
>> 2015-05-13T14:14:58.163473+00:00 uk3 kern.warning kernel [<ffffffff81645b18>] ? drbd_send_all+0xe/0x23
>> 2015-05-13T14:14:58.163481+00:00 uk3 kern.warning kernel [<ffffffff81647099>] ? _drbd_no_send_page+0x47/0x5d
>> 2015-05-13T14:14:58.163483+00:00 uk3 kern.warning kernel [<ffffffff81647671>] ? drbd_send_dblock+0x2e1/0x4ab
>> 2015-05-13T14:14:58.163485+00:00 uk3 kern.warning kernel [<ffffffff8163de54>] ? mod_rq_state+0x463/0x4e1
>> 2015-05-13T14:14:58.163487+00:00 uk3 kern.warning kernel [<ffffffff818f8229>] ? _raw_spin_lock_irq+0xc/0x65
>> 2015-05-13T14:14:58.163503+00:00 uk3 kern.warning kernel [<ffffffff8162c72b>] ? dequeue_work_batch+0x63/0x7d
>> 2015-05-13T14:14:58.163507+00:00 uk3 kern.warning kernel [<ffffffff8162cab6>] ? wait_for_work+0x59/0x2e0
>> 2015-05-13T14:14:58.163509+00:00 uk3 kern.warning kernel [<ffffffff8163044b>] ? w_send_dblock+0xd3/0x139
>> 2015-05-13T14:14:58.163511+00:00 uk3 kern.warning kernel [<ffffffff816315a6>] ? drbd_worker+0x124/0x302
>> 2015-05-13T14:14:58.163524+00:00 uk3 kern.warning kernel [<ffffffff81644d53>] ? w_complete+0x13/0x13
>> 2015-05-13T14:14:58.163526+00:00 uk3 kern.warning kernel [<ffffffff81644d9a>] ? drbd_thread_setup+0x47/0x10c
>> 2015-05-13T14:14:58.163528+00:00 uk3 kern.warning kernel [<ffffffff81644d53>] ? w_complete+0x13/0x13
>> 2015-05-13T14:14:58.163530+00:00 uk3 kern.warning kernel [<ffffffff810ecfb0>] ? kthread+0xca/0xd2
>> 2015-05-13T14:14:58.163532+00:00 uk3 kern.warning kernel [<ffffffff810ecee6>] ? kthread_freezable_should_stop+0x40/0x40
>> 2015-05-13T14:14:58.163534+00:00 uk3 kern.warning kernel [<ffffffff818f86d8>] ? ret_from_fork+0x58/0x90
>> 2015-05-13T14:14:58.163536+00:00 uk3 kern.warning kernel [<ffffffff810ecee6>] ? kthread_freezable_should_stop+0x40/0x40
>> 2015-05-13T14:14:58.163547+00:00 uk3 kern.warning kernel Code: eb 2b 4c 39 42 08 4c 89 c0 48 0f 46 42 08 48 85 c0 74 1a 49 01 c1 48 8b 32 48 89 c1 4d 89 ca 49 29 c0 48 89 c3 49 29 c2 4c 89 d7 <f3> a4 48 83 c2 10 4d 85 c0 48 8d 42 f0 75 c8 48 3b 58 08 75 05
>> 2015-05-13T14:14:58.163551+00:00 uk3 kern.alert kernel RIP  [<ffffffff8157804f>] copy_from_iter+0x140/0x24e
>> 2015-05-13T14:14:58.163553+00:00 uk3 kern.warning kernel RSP <ffff880075bd3ae0>
>> 2015-05-13T14:14:58.163555+00:00 uk3 kern.warning kernel CR2: 0000000000000003
>> 2015-05-13T14:14:58.163557+00:00 uk3 kern.warning kernel ---[ end trace 74bd7ba7a08a9e0b ]---
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