[Bug 1443542] Re: curtin race on vivid when /dev/sda1 doesn't exist

[Scott Moser]

** Description changed:

+ === Begin SRU Template ===
+ [Description]
+ Installation fails, with log information showing:
+ 
+   Unexpected error while running command.
+   Command: ['mkfs.ext4', '-q', '-L', 'cloudimg-rootfs', '/dev/sda1']
+   Exit code: 1
+   Reason: -
+   Stdout: ''
+   Stderr: ''
+   Installation failed with exception: Unexpected error while running command.
+   Command: ['curtin', 'block-meta', 'simple']
+ 
+ This is a result of curtin having done:
+  a.) partition the disk
+  b.) invoke wipefs on the block device with an offset to where the partition started
+ 
+ The intent of that was to ensure that there were no fileystem signatures
+ or other interesting metadata (lvm, raid) on the partition.
+ 
+ The issue was two fold:
+  a.) wipefs always invokes rereadpt on the disk it wipes
+  b.) wipefs opened the block device, not the partition.
+ 
+ Both of these things cause a flurry of udev events that may result in
+ the device having an open filehandle, and thus mkfs refusing to create a
+ filesystem on it.
+ 
+ The solution is to replace 'wipefs' with our own 'wipe_partition' that
+ does not open the block device, but rather only the partition and does
+ not invoke rereadpt.
+ 
+ [Impact]
+ Installation fails occasionally.
+ 
+ [Test Case]
+ In the original bug-opener's environment it fails fairly reliably under heavy host load using vmware.  He would do a deploy to several guests on the same host at the same time and this would reproduce.  Unfortunately I was unable to come up with a test case in a less complex environment.
+ 
+ [Regression Potential]
+ Not specifically a regression, but it is possible that we need additional 'udevadm settle' after the internal 'wipe_partition'
+ 
+ === End SRU Template ===
+ 
  The file /dev/sda1 does not exist and no size was specified.
  Unexpected error while running command.
  Command: ['mkfs.ext4', '-q', '-L', 'cloudimg-rootfs', '/dev/sda1']
  Exit code: 1
  Reason: -
  Stdout: ''
  Stderr: ''
  Installation failed with exception: Unexpected error while running command.
  Command: ['curtin', 'block-meta', 'simple']
  Exit code: 3
  Reason: -
  Stdout: b"The file /dev/sda1 does not exist and no size was specified.\nUnexpected error while running command.\nCommand: ['mkfs.ext4', '-q', '-L', 'cloudimg-rootfs', '/dev/sda1']\nExit code: 1\nReason: -\nStdout: ''\nStderr: ''\n"
  Stderr: ''
  
  This happened 4 out of 10 times when Ryan tested it.
  
  Could this be a race condition because /dev/sda1 hasn't had time to come
  into existence between when curtin partitions the disk and when curtin
  tries to create a filesystem on the partition?

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https://bugs.launchpad.net/bugs/1443542

Title:
  curtin race on vivid when /dev/sda1 doesn't exist

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