linux-kernel - Re: [PATCH v10 4/4] ipc: Add a cyclic mode for id generation

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Message-ID: <655c9c3f-fd53-f932-64fd-cd9fa4d1168c@redhat.com>
Date:   Thu, 8 Nov 2018 16:38:12 -0500
From:   Waiman Long <longman@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-doc@...r.kernel.org,
        Al Viro <viro@...iv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Takashi Iwai <tiwai@...e.de>, Davidlohr Bueso <dbueso@...e.de>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: Re: [PATCH v10 4/4] ipc: Add a cyclic mode for id generation

On 11/06/2018 08:02 AM, Matthew Wilcox wrote:
> On Mon, Nov 05, 2018 at 10:43:46AM -0500, Waiman Long wrote:
>> The idea of using the cyclic mode to reduce id reuse came from Manfred
>> Spraul <manfred@...orfullife.com>. There may be a little bit of
>> additional memory/performance overhead in doing cyclic id allocation,
>> but it is a slow path anyway and a bit of overhead shouldn't be an issue.
>>
>> This patch differs from his as the cyclic mode is not the default and
>> has to be explicitly opted in for users who want that.
> I really don't like the "make the sysadmin choose" approach.  It's
> shifting blame to someone who has no idea what the tradeoffs are.
> We should try to get it right rather than force more people to learn
> why we're incapable of making the right decision for them.
>
My patch is conservative as there will be no behavior change by default.
I won't mind changing the default to cyclic if we all agree.

Cheers,
Longman