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[Ponnuvel Palaniyappan <1913284@xxxxxxxxxxxxxxxxxx>]

VERIFICAION DONE

And FAILED for Focal.

1. Installed Focal
2. wipefs two devices: one cache and one backing
3. Setup a cache device on a nvme drive (/dev/nvme0n1p1)
4. Setup a backing device a hdd partition (/dev/sdb1)
5. Create a cache setup: sudo make-bcache -B /dev/sdb1 -C /dev/nvme0n1p1
6. Enable proposed and install latest sosreport
7. Generate report with sosreport -a --all-logs


# ls -l /dev/sdb1 
brw-rw---- 1 root disk 8, 17 Feb 25 22:48 /dev/sdb1
# ls -l /dev/bcache0 
brw-rw---- 1 root disk 252, 0 Feb 25 22:48 /dev/bcache0
# dpkg -l | grep sosreport
ii  sosreport                            4.0-1~ubuntu0.20.04.4                 amd64        Set of tools to gather troubleshooting data from a system

bcache module is loaded:
# lsmod | grep bcache
bcache                245760  3
crc64                  16384  1 bcache


But generated sosreport doesn't contain the bcache stats.
Looking at the "verbose" output (-v option), bcache plugin isn't triggered at all on Focal.

The tests originally done (when submitting patches to upstream) still
works with latest bcache.py on Bionic.


** Tags removed: verification-needed-focal
** Tags added: verification-failed-focal

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https://bugs.launchpad.net/bugs/1913284

Title:
  [plugin] [bcache] add a new bcache plugin

Status in sosreport package in Ubuntu:
  Fix Released
Status in sosreport source package in Bionic:
  New
Status in sosreport source package in Focal:
  Fix Committed
Status in sosreport source package in Groovy:
  Fix Committed
Status in sosreport source package in Hirsute:
  Fix Released

Bug description:
  [Impact]

  Gather bcache stats as part of sos report.

  Bcache is often deployed as a "frontend" (typically using SSDs) for
  Ceph cluster's with HDDs to improve performance. When we are dealing
  with bcache performance or need to debug bcache, these stats are
  essential to identify the problem. The newly added plugin collects
  various stats on bcache.

  
  [Test Case]

  It's a new plugin. When sosreport is run on a system with bcache, a
  number of small files from /sys/fs/bcache and /sys/block/bcache should
  be collected with this plugin in place. On systems, without bcache,
  this should be a no-op.

  
  [Where problems could occur]

  Worst case scenarios could be:
  - As with any plugin, this plugin, in theory, could potentially run indefinitely and timeout.
  - Affect performance when run on a live system. There's one known case where querying the proiorty_stats [0] had such a problem. But it's not collected as part of this plugin.

  But otherwise, the stats collection of bcache devices (even if there
  are many bcache devices deployed on a system) shouldn't affect
  anything on a live system and shouldn't get anywhere closer to
  timeout.

  
  [Other Info]
   
  upstream PR (merged): https://github.com/sosreport/sos/pull/2384


  [0] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1840043

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