[Bugs] [Bug 1615096] ./tests/bugs/quick-read/bug-846240.t fails spuriously

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1615096

Worker Ant <bugzilla-bot at gluster.org> changed:

           What    |Removed                     |Added
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             Status|POST                        |MODIFIED



--- Comment #2 from Worker Ant <bugzilla-bot at gluster.org> ---
COMMIT: https://review.gluster.org/20710 committed in master by "Shyamsundar
Ranganathan" <srangana at redhat.com> with a commit message-
tests/quick-read/bug-846240.t: fix a wrong test

Earlier this test did following things on M0 and M1 mounted on same
volume:
1 create file  M0/testfile
2 open an fd on M0/testfile
3 remove the file from M1, M1/testfile
4 echo "data" >> M0/testfile

The test expects appending data to M0/testfile to fail. However,
redirector ">>" creates a file if it doesn't exist. So, the only
reason test succeeded was due to lookup succeeding due to stale stat
in md-cache. This hypothesis is verified by two experiments:
* Add a sleep of 10 seconds before append operation. md-cache cache
  expires and lookup fails followed by creation of file and hence append
  succeeds to new file.
* set md-cache timeout to 600 seconds and test never fails even with
  sleep 10 before append operation. Reason is stale stat in md-cache
  survives sleep 10.

So, the spurious nature of failure was dependent on whether lookup is
done when stat is present in md-cache or not.

The actual test should've been to write to the fd opened in step 2
above. I've changed the test accordingly. Note that this patch also
remounts M0 after initial file creation as open-behind disables
opening-behind on witnessing a setattr on the inode and touch involves
a setattr. On remount, create operation is not done and hence file is
opened-behind.

Change-Id: I739f255e0a62ff0024f0824dad3539974955df99
Signed-off-by: Raghavendra G <rgowdapp at redhat.com>
Fixes: bz#1615096

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