linux-kernel - Re: [PATCH v4 00/10] hugetlbfs: add fallocate support

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Message-ID: <20150723151707.GB7795@akamai.com>
Date:	Thu, 23 Jul 2015 11:17:07 -0400
From:	Eric B Munson <emunson@...mai.com>
To:	Mike Kravetz <mike.kravetz@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Davidlohr Bueso <dave@...olabs.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Aneesh Kumar <aneesh.kumar@...ux.vnet.ibm.com>,
	Hillf Danton <hillf.zj@...baba-inc.com>,
	Christoph Hellwig <hch@...radead.org>,
	Michal Hocko <mhocko@...e.cz>, emunson@...bm.net
Subject: Re: [PATCH v4 00/10] hugetlbfs: add fallocate support

On Wed, 22 Jul 2015, Mike Kravetz wrote:

> On 07/22/2015 03:30 PM, Andrew Morton wrote:
> >On Wed, 22 Jul 2015 15:19:54 -0700 Davidlohr Bueso <dave@...olabs.net> wrote:
> >
> >>>
> >>>I didn't know that libhugetlbfs has tests.  I wonder if that makes
> >>>tools/testing/selftests/vm's hugetlbfstest harmful?
> >>
> >>Why harmful? Redundant, maybe(?).
> >
> >The presence of the in-kernel tests will cause people to add stuff to
> >them when it would be better if they were to apply that effort to
> >making libhugetlbfs better.  Or vice versa.
> >
> >Mike's work is an example.  Someone later makes a change to hugetlbfs, runs
> >the kernel selftest and says "yay, everything works", unaware that they
> >just broke fallocate support.
> >
> >>Does anyone even use selftests for
> >>hugetlbfs regression testing? Lets see, we also have these:
> >>
> >>- hugepage-{mmap,shm}.c
> >>- map_hugetlb.c
> >>
> >>There's probably a lot of room for improvement here.
> >
> >selftests is a pretty scrappy place.  It's partly a dumping ground for
> >things so useful test code doesn't just get lost and bitrotted.  Partly
> >a framework so people who add features can easily test them. Partly to
> >provide tools to architecture maintainers when they wire up new
> >syscalls and the like.
> >
> >Unless there's some good reason to retain the hugetlb part of
> >selftests, I'm thinking we should just remove it to avoid
> >distracting/misleading people.  Or possibly move the libhugetlbfs test
> >code into the kernel tree and maintain it there.
> 
> Adding Eric as he is the libhugetlbfs maintainer.
> 
> I think removing the hugetlb selftests in the kernel and pointing
> people to libhugetlbfs is the way to go.  From a very quick scan
> of the selftests, I would guess libhugetlbfs covers everything
> in those tests.
> 
> I'm willing to verify the testing provided by selftests is included
> in libhugetlbfs, and remove selftests if that is the direction we
> want to take.

I would rather see the test suite stay in the library, there are a
number of tests that rely on infrastructure in the library that is not
available in selftests.

I am happy to help with any tests that need to be added/modified in the
library to cover.


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