[OmniOS-discuss] LOFS LX chdir bug with steps to reproduce

[Mini Trader]

I spent a bit of time yesterday using dtrace and looking at the source.  I
believe I found why the system is falsely reporting that the current
directory does not exist and have created a simple program to reproduce the
problem.  The problem seems to be related to when v_path in the vnode
struct goes above a certain number of characters.  This will only break on
LOFS if inside the LX zone.  Every time a program performs a chdir('..')
and up to another dir the system stored working directory is falsely
growing.

Here are the steps to reproduce.

1. Mount a ZFS dataset via LOFS for your LX zone.
2. Create a directory in the dataset called test
3. In the test directory create another directory called 'Chdir Test'
4. Run the program below.  All this is doing is going up a directory and
dropping down a directory.  We want to fill up v_path.
5. The program will bomb before iteration 1000.  Really there should be no
limit.


import os
import time

#time.sleep(15)
os.chdir('/tank/bigtest/test')
for i in xrange(1000):
    print i
    os.chdir('Chdir Test')
    os.getcwd()
    os.chdir('..')

I used the following dtrace to get insight into what was happening (ran it
from global zone).

dtrace -n 'fbt:genunix:vnodetopath_common:entry /pid == $target/ {
printf("%s\n",stringof(args[1]->v_path)) }' -q -x strsize=4k -p 22482

Uncomment the sleep line so that you can determine the PID when running
dtrace.
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