[SRU][Xenial][Artful][Bionic][v2][PATCH 0/1] UBUNTU: SAUCE: (no-up) bcache: decouple emitting a cached_dev CHANGE uevent

Joseph Salisbury joseph.salisbury at canonical.com
Mon Dec 11 14:12:00 UTC 2017

BugLink: http://bugs.launchpad.net/bugs/1729145

== SRU Justification ==
This bug is preventing /dev/bcache/by-uuid links from being created after reboot.
It appears that since the initramfs loads the bcache module which probes and 
finds all of the cache devices and backing devices then once the rootfs is
mounted and udev gets to run, the bcache kernel module does not emit the
CACHED_UUID value into the environment if the underlying devices are already registered.     

With this patch, instead of just failing with "device already registered"
the kernel emits another uevent with CACHED_UUID which would be processed
another time to set up a symlink.

This patch is not yet upstream, but we will submit it there as well.  However,
requesting this a SAUCE patch until it lands upstream.

Zesty also requires this patch.  However, it needs a prereq commit, so it will
be SRU'd separately.

== Fix ==
Patch from Ryan Harper <ryan.harper at canonical.com>:
bcache: decouple emitting a cached_dev CHANGE uevent

== Regression Potential ==
There is some risk of regression, since this is new code.   However, it is
limited to the bcache.

== Test Case ==
A test kernel was built with this patch and tested by the original bug reporter.
The bug reporter states the test kernel resolved the bug.

Ryan Harper (1):
  bcache: decouple emitting a cached_dev CHANGE uevent

 drivers/md/bcache/bcache.h |  1 +
 drivers/md/bcache/super.c  | 53 +++++++++++++++++++++++++++++++++++++---------
 2 files changed, 44 insertions(+), 10 deletions(-)


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