[PATCH 0/1][SRU][BIONIC] Fix nbd I/O errors on client shutdown (LP: #1822247)

[Colin King]

From: Colin Ian King <colin.king at canonical.com>

BugLink: https://bugs.launchpad.net/bugs/1822247

== SRU Justification, BIONIC ==

[Impact]

Running the autotest regression test ubuntu_nbd_smoke occasionally
trips I/O errors such as:

[ 700.668758] print_req_error: I/O error, dev nbd0, sector 0
[ 700.668840] Buffer I/O error on dev nbd0, logical block 0, async
              page read

This happens when the nbd client detaches and the backing store is
removed. The fix is to ensure a rescan occurs.

[Fix]

Upstream fix fe1f9e6659ca6124f500a0f829202c7c902fab0c (" nbd:
fix how we set bd_invalidated"). If a disconnect action happens the
partition table gets invalidated and rescanned properly.

[Testcase]

Without the fix running the Ubuntu Kernel Team nbd smoke test will
occasionally trip the bug and the error message from the kernel
appears and the test fails. With the fix, this test has been run
tens of times without showing the failure.

To test run:
autotest/client/local-test autotest/client/tests/ubuntu_nbd_smoke_test/control

[Regression Potential]

This fix touches just the NBD driver and has been upstream since
May 2018 without any subsequent bug reports against it, so it is a
known good fix. At most it sets the bd_invalidated flag more
aggressively, so the rescan will occur, so I believe the regression
potential is very limited just to ndb client connect/disconnect
activity.


Josef Bacik (1):
  nbd: fix how we set bd_invalidated

 drivers/block/nbd.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

-- 
2.20.1