linux-kernel - Re: [RESEND PATCH 2/2] userfaultfd: selftest: Add tests for UFFD_FREATURE

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Message-ID: <20170726142723.GW29716@redhat.com>
Date:   Wed, 26 Jul 2017 16:27:23 +0200
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Prakash Sangappa <prakash.sangappa@...cle.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-api@...r.kernel.org, rppt@...ux.vnet.ibm.com,
        akpm@...ux-foundation.org, mike.kravetz@...cle.com
Subject: Re: [RESEND PATCH 2/2] userfaultfd: selftest: Add tests for
 UFFD_FREATURE_SIGBUS

On Tue, Jul 25, 2017 at 12:47:42AM -0400, Prakash Sangappa wrote:
> Signed-off-by: Prakash Sangappa <prakash.sangappa@...cle.com>
> ---
>  tools/testing/selftests/vm/userfaultfd.c |  121 +++++++++++++++++++++++++++++-
>  1 files changed, 118 insertions(+), 3 deletions(-)

Like Mike said, some comment about the test would be better, commit
messages are never one liners in the kernel.

> @@ -408,6 +409,7 @@ static int copy_page(int ufd, unsigned long offset)
>  				userfaults++;
>  			break;
>  		case UFFD_EVENT_FORK:
> +			close(uffd);
>  			uffd = msg.arg.fork.ufd;
>  			pollfd[0].fd = uffd;
>  			break;

Isn't this fd leak bugfix independent of the rest of the changes? The
only side effects should have been that it could run out of fds, but I
assume this was found by source review as I doubt it could run out of fds.
This could be splitted off in a separate patch.

Overall it looks a good test also exercising UFFD_EVENT_FORK at the
same time.

Thanks,
Andrea