linux-kernel - Re: [PATCH 0/4] get_user_pages*() and RDMA: first steps

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Message-ID: <20181001153101.GA23286@ziepe.ca>
Date:   Mon, 1 Oct 2018 09:31:01 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Dave Chinner <david@...morbit.com>
Cc:     Jerome Glisse <jglisse@...hat.com>,
        John Hubbard <jhubbard@...dia.com>, john.hubbard@...il.com,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jan Kara <jack@...e.cz>, Al Viro <viro@...iv.linux.org.uk>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        Christian Benvenuti <benve@...co.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>
Subject: Re: [PATCH 0/4] get_user_pages*() and RDMA: first steps

On Mon, Oct 01, 2018 at 04:11:27PM +1000, Dave Chinner wrote:

> This reminds me so much of Linux mmap() in the mid-2000s - mmap()
> worked for ext3 without being aware of page faults, so most mm/
> developers at the time were of the opinion that all the other
> filesystems should work just fine without being aware of page
> faults.

This is probably because RDMA was introduced around that time, before
page_mkwrite was added.. It kind of sounds like page_mkwrite() broke
all the writing get_user_pages users and it wasn't realized at the
time.

BTW, we are hosting a session on this at Plumbers during the RDMA
track, hope everyone interested will be able to attend.

Jason