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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

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** Changed in: linux (Ubuntu)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/621437

Title:
  libata stalling under heavy IO

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  Lucid Server i386

  uname -a
  Linux tony-server 2.6.32-24-generic-pae #41-Ubuntu SMP Thu Aug 19 02:43:57 UTC 2010 i686 GNU/Linux

  /proc/version_signature
  Ubuntu 2.6.32-24.41-generic-pae 2.6.32.15+drm33.5

  
  Under heavy IO load to a RAID5 array, I'm experiencing high iowait

  Syslog reports:

  Aug 20 21:44:17 tony-server kernel: [ 3902.000092] ata6.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
  Aug 20 21:44:17 tony-server kernel: [ 3902.013734] ata6.01: failed command: READ DMA
  Aug 20 21:44:17 tony-server kernel: [ 3902.027159] ata6.01: cmd c8/00:20:3f:6b:6a/00:00:00:00:00/fb tag 0 dma 16384 in
  Aug 20 21:44:17 tony-server kernel: [ 3902.027161]          res 40/00:ff:00:00:00/00:00:00:00:00/50 Emask 0x4 (timeout)
  Aug 20 21:44:17 tony-server kernel: [ 3902.079963] ata6.01: status: { DRDY }
  Aug 20 21:44:22 tony-server kernel: [ 3907.132036] ata6: link is slow to respond, please be patient (ready=0)
  Aug 20 21:44:27 tony-server kernel: [ 3912.116037] ata6: device not ready (errno=-16), forcing hardreset
  Aug 20 21:44:27 tony-server kernel: [ 3912.116053] ata6: soft resetting link
  Aug 20 21:44:28 tony-server kernel: [ 3912.304511] ata6.00: configured for UDMA/33
  Aug 20 21:44:28 tony-server kernel: [ 3912.320846] ata6.01: configured for UDMA/33
  Aug 20 21:44:28 tony-server kernel: [ 3912.320859] ata6.01: device reported invalid CHS sector 0
  Aug 20 21:44:28 tony-server kernel: [ 3912.320873] ata6: EH complete

  These occur repeatedly every few minutes while RAID array is being written to
  If I forcefully limit the client write speed to 500 KiB/s or less, problem goes away

  RAID array is EXT4 exported over NFS, and all disk activity is
  initiated by client

  Searching around, I came across this
  http://lkml.org/lkml/2010/3/9/345
  (This is linux 2.6.34, but the errors look identical to me)

  There's also a patch a few posts in from the above link

  Quick look at the Lucid kernel git repo suggests this patch is not applied to the Lucid kernel
  http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-lucid.git;a=blob_plain;f=drivers/ata/libata-sff.c;hb=HEAD
  (I hope I'm looking in the right tree...?)

  ProblemType: Bug
  DistroRelease: Ubuntu 10.04
  Package: linux-image-2.6.32-24-generic-pae 2.6.32-24.41
  Regression: Yes
  Reproducible: No
  ProcVersionSignature: Ubuntu 2.6.32-24.41-generic-pae 2.6.32.15+drm33.5
  Uname: Linux 2.6.32-24-generic-pae i686
  Architecture: i386
  Date: Fri Aug 20 22:57:54 2010
  ProcEnviron:
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  SourcePackage: linux

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