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 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. 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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