linux-kernel - Re: [PATCH] hugetlbfs: add O

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Message-ID: <eb6206ee-eb2e-ffbc-3963-d80eec04119c@oracle.com>
Date:   Mon, 21 Oct 2019 10:17:13 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Piotr Sarna <p.sarna@...n.pl>
Cc:     Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] hugetlbfs: add O_TMPFILE support

On 10/15/19 4:37 PM, Mike Kravetz wrote:
> On 10/15/19 3:50 AM, Michal Hocko wrote:
>> On Tue 15-10-19 11:01:12, Piotr Sarna wrote:
>>> With hugetlbfs, a common pattern for mapping anonymous huge pages
>>> is to create a temporary file first.
>>
>> Really? I though that this is normally done by shmget(SHM_HUGETLB) or
>> mmap(MAP_HUGETLB). Or maybe I misunderstood your definition on anonymous
>> huge pages.
>>
>>> Currently libraries like
>>> libhugetlbfs and seastar create these with a standard mkstemp+unlink
>>> trick,
> 
> I would guess that much of libhugetlbfs was writen before MAP_HUGETLB
> was implemented.  So, that is why it does not make (more) use of that
> option.
> 
> The implementation looks to be straight forward.  However, I really do
> not want to add more functionality to hugetlbfs unless there is specific
> use case that needs it.

It was not my intention to shut down discussion on this patch.  I was just
asking if there was a (new) use case for such a change.  I am checking with
our DB team as I seem to remember them using the create/unlink approach for
hugetlbfs in one of their upcoming models.  

Is there a new use case you were thinking about?
-- 
Mike Kravetz