linux-kernel - Re: [PATCH v2 5/9] userfaultfd/selftests: use memfd

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Message-ID: <20210413201649.GE4440@xz-x1>
Date:   Tue, 13 Apr 2021 16:16:49 -0400
From:   Peter Xu <peterx@...hat.com>
To:     Axel Rasmussen <axelrasmussen@...gle.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Joe Perches <joe@...ches.com>,
        Lokesh Gidra <lokeshgidra@...gle.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Shaohua Li <shli@...com>, Shuah Khan <shuah@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Wang Qing <wangqing@...o.com>, linux-api@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org,
        Brian Geffon <bgeffon@...gle.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Oliver Upton <oupton@...gle.com>
Subject: Re: [PATCH v2 5/9] userfaultfd/selftests: use memfd_create for shmem
 test type

On Mon, Apr 12, 2021 at 10:17:17PM -0700, Axel Rasmussen wrote:
> This is a preparatory commit. In the future, we want to be able to setup
> alias mappings for area_src and area_dst in the shmem test, like we do
> in the hugetlb_shared test. With a VMA obtained via
> mmap(MAP_ANONYMOUS | MAP_SHARED), it isn't clear how to do this.
> 
> So, mmap() with an fd, so we can create alias mappings. Use memfd_create
> instead of actually passing in a tmpfs path like hugetlb does, since
> it's more convenient / simpler to run, and works just as well.
> 
> Future commits will:
> 
> 1. Setup the alias mappings.
> 2. Extend our tests to actually take advantage of this, to test new
>    userfaultfd behavior being introduced in this series.
> 
> Also, a small fix in the area we're changing: when the hugetlb setup
> fails in main(), pass in the right argv[] so we actually print out the
> hugetlb file path.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@...gle.com>

Reviewed-by: Peter Xu <peterx@...hat.com>

-- 
Peter Xu