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Date:   Tue, 2 Feb 2021 13:13:27 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Peter Xu <peterx@redhat.com>
Cc:     20200918161902.GX8409@ziepe.ca,
        Linus Torvalds <torvalds@linux-foundation.org>,
        John Hubbard <jhubbard@nvidia.com>,
        Leon Romanovsky <leonro@nvidia.com>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Maya B . Gokhale" <gokhale2@llnl.gov>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        Marty Mcfadden <mcfadden8@llnl.gov>,
        Kirill Shutemov <kirill@shutemov.name>,
        Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
        Jan Kara <jack@suse.cz>, Kirill Tkhai <ktkhai@virtuozzo.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Christoph Hellwig <hch@lst.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Zhang, Wei" <wzam@amazon.com>
Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification
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On Tue, Feb 02, 2021 at 12:05:36PM -0500, Peter Xu wrote:

> > Gal, you could also MADV_DONTFORK this range if you are explicitly
> > allocating them via special mmap.
> 
> Yeah I wanted to mention this one too but I just forgot when reply: the issue
> thread previously pasted smells like some people would like to drop
> MADV_DONTFORK, but if it's able to still be applied I don't know why
> not..

I want to drop the MADV_DONTFORK for dynamic data memory allocated by
the application layers (eg with malloc) without knowledge of how they
will be used.

This case is a buffer internal to the communication system that we
know at allocation time how it will be used; so an explicit,
deliberate, MADV_DONTFORK is fine

Jason