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[Mel Dee <1217189@xxxxxxxxxxxxxxxxxx>]

IMO, this bug *is* a duplicate of #1215513. The real problem is that the
zram kernel module creates a block device with a bad sector at the end.
When you try to swap on it, anything can happen, from system lockdowns
to program crashes to nothing (e.g., if you have so much RAM you never
get to use the last sector of /dev/zram0).

I posted detailed findings at #55 on the other bug's page.

Kenneth (#51): 'mkswap' run on the entire block device /dev/zram0 DOES
NOT create a visible swap partition for you to see with 'fdisk -l'. The
fact that you don't see a swap partition on it DOES NOT mean /dev/zram0
is not being swapped on. Check this with 'swapon -s' (and disable it if
it's there!) To see this, and also the bad 4KB sector, try this (first
swapoff and rmmod):

$ sudo modprobe zram
$ echo '1024^3' | bc | sudo tee /sys/block/zram0/disksize                                                                                     
1073741824                                                                                                                                                                    
$ sudo mkswap -c /dev/zram0
one bad page                                                                                                                                                                  
Setting up swapspace version 1, size = 1048568 KiB
no label, UUID=487d15c0-07ce-46d1-b632-492611e2a13a
$ sudo mkswap /dev/zram0
Setting up swapspace version 1, size = 1048572 KiB
no label, UUID=9fa2c2df-d69c-4282-87ad-7c3219e50832
$ sudo fdisk -l /dev/zram0
Note: sector size is 4096 (not 512)

Disk /dev/zram0: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 16 cylinders, total 262144 sectors
Units = sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Disk /dev/zram0 doesn't contain a valid partition table

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https://bugs.launchpad.net/bugs/1217189

Title:
  Buffer I/O error on device zram0

Status in “linux” package in Ubuntu:
  Confirmed
Status in “linux-lts-raring” package in Ubuntu:
  Confirmed

Bug description:
  This is on linux-image-generic-lts-raring (which I recently upgraded
  to 3.8.0-29; the problem didn't occur before upgrading AFAIR)

  I see this junk in my dmesg when creating / formatting a zram swap,
  and then periodically. Then at some point after heavy swapping
  incidents, the machine locks up. "Correlation does not imply
  causation, but it does waggle its eyebrows suggestively" and all that.

  ---

  zram: module is from the staging directory, the quality is unknown, you have been warned.
  zram: num_devices not specified. Using default: 1
  zram: Creating 1 devices
  Adding 1031648k swap on /dev/zram0.  Priority:100 extents:1 across:1031648k SS
  ...
  Buffer I/O error on device zram0, logical block 257912 [repeated 10 times]
  ...
  BUG: scheduling while atomic: rsyslogd/1439/0x00000001
  Pid: 1439, comm: rsyslogd Tainted: PF       WC O 3.8.0-29-generic #42~precise1-Ubuntu
  [20931.796635] Pid: 1439, comm: rsyslogd Tainted: PF       WC O 3.8.0-29-generic #42~precise1-Ubuntu
  [20931.796638] Call Trace:
  [20931.796649]  [<c1619449>] __schedule_bug+0x52/0x5e
  [20931.796653]  [<c162c265>] __schedule+0x575/0x5f0
  [20931.796660]  [<f8439e06>] ? zram_make_request+0xe6/0x100 [zram]
  [20931.796666]  [<c111c38d>] ? release_pages+0x18d/0x1c0
  [20931.796669]  [<c162c573>] schedule+0x23/0x60
  [20931.796673]  [<c162d0fd>] rwsem_down_failed_common+0x9d/0xf0
  [20931.796677]  [<c162d162>] rwsem_down_write_failed+0x12/0x20
  [20931.796681]  [<c12f809a>] call_rwsem_down_write_failed+0x6/0x8
  [20931.796685]  [<c162ba44>] ? down_write+0x24/0x30
  [20931.796689]  [<f8439169>] zram_slot_free_notify+0x29/0x50 [zram]
  [20931.796693]  [<f8439140>] ? zram_stat64_inc+0x30/0x30 [zram]
  [20931.796700]  [<c11460bc>] swap_entry_free+0xdc/0x170
  [20931.796703]  [<c162d100>] ? rwsem_down_failed_common+0xa0/0xf0
  [20931.796708]  [<c1146458>] swap_free+0x28/0x40
  [20931.796712]  [<c1134ba0>] do_swap_page+0x390/0x6f0
  [20931.796717]  [<c10180f8>] ? sched_clock+0x8/0x10
  [20931.796721]  [<c11365aa>] handle_pte_fault+0x21a/0x2b0
  [20931.796726]  [<c10451e1>] ? kmap_atomic_prot+0xf1/0x120
  [20931.796730]  [<c113746a>] handle_mm_fault+0x1fa/0x2d0
  [20931.796735]  [<c1630ad0>] __do_page_fault+0x190/0x4f0
  [20931.796740]  [<c12f63bc>] ? sprintf+0x1c/0x20
  [20931.796744]  [<c104c132>] ? print_time.part.4+0x82/0xc0
  [20931.796748]  [<c1630e30>] ? __do_page_fault+0x4f0/0x4f0
  [20931.796752]  [<c1630e3d>] do_page_fault+0xd/0x10
  [20931.796756]  [<c162dc17>] error_code+0x67/0x6c
  [20931.796759]  [<c12f8716>] ? __copy_to_user_ll+0x46/0x70
  [20931.796763]  [<c12f8970>] copy_to_user+0x40/0x60
  [20931.796767]  [<c104e218>] syslog_print+0xc8/0x210
  [20931.796770]  [<c104eae6>] do_syslog+0x206/0x390
  [20931.796775]  [<c106d570>] ? add_wait_queue+0x50/0x50
  [20931.796780]  [<c11c3680>] ? kmsg_poll+0x50/0x50
  [20931.796784]  [<c11c36d0>] kmsg_read+0x50/0x60
  [20931.796788]  [<c11b6584>] proc_reg_read+0x64/0xa0
  [20931.796793]  [<c116469c>] vfs_read+0x8c/0x160
  [20931.796797]  [<c10a898d>] ? sys_futex+0xed/0x130
  [20931.796801]  [<c11b6520>] ? proc_reg_write+0xa0/0xa0
  [20931.796805]  [<c11647b7>] sys_read+0x47/0x80
  ...
  [30855.181542] Write-error on swap-device (251:0:131064)
  [43457.030155] Write-error on swap-device (251:0:131064)
  [43705.090381] Buffer I/O error on device zram0, logical block 16383

  Anyway, there's a couple of lkml messages related to this "Buffer I/O
  error on device zram0", please investigate

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: linux-image-3.8.0-29-generic 3.8.0-29.42~precise1
  ProcVersionSignature: Ubuntu 3.8.0-29.42~precise1-generic 3.8.13.5
  Uname: Linux 3.8.0-29-generic i686
  NonfreeKernelModules: nvidia
  ApportVersion: 2.0.1-0ubuntu17.4
  Architecture: i386
  Date: Tue Aug 27 07:33:37 2013
  EcryptfsInUse: Yes
  MarkForUpload: True
  ProcEnviron:
   TERM=rxvt
   LC_COLLATE=C
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: linux-lts-raring
  UpgradeStatus: No upgrade log present (probably fresh install)
  --- 
  AlsaVersion: Advanced Linux Sound Architecture Driver Version k3.8.0-29-lowlatency.
  ApportVersion: 2.0.1-0ubuntu17.4
  Architecture: i386
  AudioDevicesInUse:
   USER        PID ACCESS COMMAND
   /dev/snd/controlC0:  muresan   29305 F.... pulseaudio
   /dev/snd/pcmC0D0p:   muresan   29305 F...m pulseaudio
   /dev/snd/controlC1:  muresan   29305 F.... pulseaudio
  CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
  Card0.Amixer.info:
   Card hw:0 'Intel'/'HDA Intel at 0xfebfc000 irq 44'
     Mixer name	: 'SigmaTel STAC9205'
     Components	: 'HDA:838476a0,102801f1,00100204 HDA:14f12c06,14f1000f,00100000'
     Controls      : 26
     Simple ctrls  : 12
  Card1.Amixer.info:
   Card hw:1 'USB'/'E-MU Systems, Inc. E-MU 0202 | USB at usb-0000:00:1d.0-2, full speed'
     Mixer name	: 'USB Mixer'
     Components	: 'USB041e:3f02'
     Controls      : 4
     Simple ctrls  : 2
  DistroRelease: Ubuntu 12.04
  EcryptfsInUse: Yes
  HibernationDevice: RESUME=UUID=88836c66-16ea-407f-8753-3190c09ca82f
  IwConfig:
   lo        no wireless extensions.
   
   eth0      no wireless extensions.
  MachineType: Dell Inc. Inspiron 1520
  MarkForUpload: True
  NonfreeKernelModules: nvidia
  Package: linux-lts-raring
  ProcEnviron:
   TERM=rxvt
   LC_COLLATE=C
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  ProcFB:
   
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.8.0-29-lowlatency root=UUID=a7047dd8-61aa-4cbe-b36d-697a5e7ee64b ro
  ProcVersionSignature: Ubuntu 3.8.0-29.21-lowlatency 3.8.13.5
  RelatedPackageVersions:
   linux-restricted-modules-3.8.0-29-lowlatency N/A
   linux-backports-modules-3.8.0-29-lowlatency  N/A
   linux-firmware                               1.79.6
  RfKill:
   0: hci0: Bluetooth
   	Soft blocked: no
   	Hard blocked: no
  StagingDrivers: zram
  Tags:  precise staging
  Uname: Linux 3.8.0-29-lowlatency i686
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups: adm admin audio cdrom davfs2 dialout dip floppy fuse lpadmin netdev plugdev powerdev sambashare scanner video
  dmi.bios.date: 02/03/2008
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: A07
  dmi.board.name: 0UW306
  dmi.board.vendor: Dell Inc.
  dmi.chassis.type: 8
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvrA07:bd02/03/2008:svnDellInc.:pnInspiron1520:pvr:rvnDellInc.:rn0UW306:rvr:cvnDellInc.:ct8:cvr:
  dmi.product.name: Inspiron 1520
  dmi.sys.vendor: Dell Inc.

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