Re: RFC: don't fail tests when mkfs options collide

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Jul 23, 2024 at 10:17:24AM -0400, Theodore Ts'o wrote:
> On Tue, Jul 23, 2024 at 03:39:04PM +0200, Christoph Hellwig wrote:
> > 
> > At least in my case it's not really by overriding.  E.g. if I force
> > an allocation group (or block group in extN terms) to a specific size
> > and then want a log that is larger than that, changing the AG size
> > is generally a bad idea, and a clear warning to the user is simply the
> > better interface.
> 
> Is it just "a bad idea", or "it won't work"?  I can imagine that
> sometimes we want to have tests that do things that are generally a
> bad idea, but it's the best way to force a particular corner case to
> happen without having to run the test gazillions of times?
> 
> I do remember some cases where when we were using a 1k block size, the
> test wouldn't actually work because the file system needed to be
> bigger or the metadata overhead ended up causing an ENOSPC too early,
> or something weird like that.  So that was a case were the merging
> would _work_, and in fact was testing a combination that we actually
> wanted to test --- but we had to adjust the test subtly so it would
> work both on a 4k block size and a 1k block size.  I don't remember
> which test it was, or we hacked it, but I'm fairly certain it's
> something we've done before.  It's messy.
> 
> > Merging the options is what we're currently doing, and it works ok
> > most of the time.  The question is what to do when it doesn't.
> 
> No matter what, it seems like we'll have to look at each of these
> tests and treat them on a per-case basis.  We could have options which
> allows the test to specify that it shouldn't be merging; but then we'd
> still have to decide what we need to do.  And what do we do if we
> don't want to merge for ext4 and xfs, but it would be useful for btrfs
> (for example) to merge the options.  It's probably also going to
> depend on which test scenarios that various file system developers'
> test setups choose to use....

The big question I have is: for at least the standard -g all runs, does
this decrease the number of tests selected?  AFAICT all it does is
converts mkfs option parsing _fail into _notrun, but a 35k shell script
patch is a lot to take in.

If it doesn't change the number of tests selected to run then I think
I'm ok with this.

--D