Re: [PATCH] generic/411: change sub-path name that's duplicate of TEST_DIR

[Eryu Guan <eguan@redhat.com>]

On Wed, Mar 08, 2017 at 12:01:33PM +0200, Amir Goldstein wrote:
> On Wed, Mar 8, 2017 at 9:26 AM, Zorro Lang <zlang@redhat.com> wrote:
> > Darrick found generic/411 golden output mismatch if use
> > TEST_DIR=/mnt. Because g/411 use some test path named
> > /mnt/XXXX/mnt1/mnt2, _filter_test_dir will replace all
> > "/mnt" things to "TEST_DIR".
> >
> > For stop this failure, change all directory names to be
> > "$seq-XXX", that's less likely to be mistaken for TEST_*
> > and SCRATCH_*.
> >
> 
> Although you have a right to choose whichever names you
> want top use for your test, this is papering over a bug.
> 
> I re-read the docuemtnation for \B:
> http://www.rexegg.com/regex-boundaries.html#bengines
> 
> To my understanding, the expression "\B$TEST_DIR" will
> match every instance of $TEST_DIR, where preceding character
> is NOT a letter, number or underscore.
> This is because $TEST_DIR must start with '/', which is not
> a letter, number or underscore.
> 
> I think it should be safe to fix _filter_test_dir and _filter_scratch.

I agreed, according to the document above, \B matches all positions
where \b doesn't match. And \b matches positions where "one side is a
word character and the other side is not", so \B matches "neither side
is a word character" and "both sides are a word character".

This is also because we canonicalized all mount points, there's no path
like //mnt/mnt1 is allowed in fstests. And this leads me to wonder if we
should canonicalize all test devices (if they're block device), to avoid
something like //dev/sda5? The double "/" will break the \B match.

Further more, if we decide to use \B to improve _filter_test_dir and
_filter_scratch, it appears to me that the fix from commit 4e965d8
("fstests: fix test and scratch filters for overlapping DEV/MNT paths")
can be discarded, the order is not a problem anymore.

Thanks for looking at this!

Eryu