linux-kernel - Re: [PATCH v3 5/7] selftests: add memfd/sealing page-pinning tests

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Date:	Sat, 19 Jul 2014 18:32:55 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Ryan Lortie <desrt@...rt.ca>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Greg Kroah-Hartman <greg@...ah.com>,
	John Stultz <john.stultz@...aro.org>,
	Lennart Poettering <lennart@...ttering.net>,
	Daniel Mack <zonque@...il.com>, Kay Sievers <kay@...y.org>,
	Tony Battersby <tonyb@...ernetics.com>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v3 5/7] selftests: add memfd/sealing page-pinning tests

Hi

On Wed, Jul 16, 2014 at 12:08 PM, Hugh Dickins <hughd@...gle.com> wrote:
> On Fri, 13 Jun 2014, David Herrmann wrote:
>
>> Setting SEAL_WRITE is not possible if there're pending GUP users. This
>> commit adds selftests for memfd+sealing that use FUSE to create pending
>> page-references. FUSE is very helpful here in that it allows us to delay
>> direct-IO operations for an arbitrary amount of time. This way, we can
>> force the kernel to pin pages and then run our normal selftests.
>>
>> Signed-off-by: David Herrmann <dh.herrmann@...il.com>
>
> I had a number of problems in getting this working (on openSUSE 13.1):
> rpm told me I had fuse installed, yet I had to download and install
> the tarball to get header files needed; then "make fuse_mnt" told me
> to add -D_FILE_OFFSET_BITS=64 to the compile flags; after which I
> got "undefined reference to `fuse_main_real'"; but then I tried
> "make run_fuse" as root, and it seemed to sort these issues out
> for itself, aside from "./run_fuse_test.sh: Permission denied" -
> which was within my bounds of comprehension unlike the rest!
>
> No complaint, thanks for providing the test (though I didn't check
> the source to convince myself that "DONE" has done what's claimed):
> some rainy day someone can get the Makefile working more smoothly,
> no need to delay the patchset for this.

_FILE_OFFSET_BITS=64 makes sense. I added it. The "undefined ref"
thing doesn't make sense to me and I cannot reproduce it. I will see
what I can do.

The "Permission denied" obviously just requires access to /dev/fuse,
as you figured out yourself.

Thanks
David
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