linux-kernel - Re: [PATCH 00/12] block/bio, fs: convert put_page() to put_user

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Message-ID: <3ab1e69f-88c6-3e16-444d-cab78c3bf1d1@nvidia.com>
Date:   Tue, 6 Aug 2019 23:38:59 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     <john.hubbard@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "David S . Miller" <davem@...emloft.net>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Eric Van Hensbergen <ericvh@...il.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Jason Wang <jasowang@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Latchesar Ionkov <lucho@...kov.net>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Christoph Hellwig <hch@....de>,
        Matthew Wilcox <willy@...radead.org>, <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        <ceph-devel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <linux-block@...r.kernel.org>, <linux-cifs@...r.kernel.org>,
        <linux-fsdevel@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
        <linux-rdma@...r.kernel.org>, <netdev@...r.kernel.org>,
        <samba-technical@...ts.samba.org>,
        <v9fs-developer@...ts.sourceforge.net>,
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 00/12] block/bio, fs: convert put_page() to
 put_user_page*()

On 8/6/19 11:34 PM, Christoph Hellwig wrote:
> On Mon, Aug 05, 2019 at 03:54:35PM -0700, John Hubbard wrote:
>> On 7/23/19 11:17 PM, Christoph Hellwig wrote:
...
>>> I think we can do this in a simple and better way.  We have 5 ITER_*
>>> types.  Of those ITER_DISCARD as the name suggests never uses pages, so
>>> we can skip handling it.  ITER_PIPE is rejected іn the direct I/O path,
>>> which leaves us with three.
>>>
>>
>> Hi Christoph,
>>
>> Are you working on anything like this?
> 
> I was hoping I could steer you towards it.  But if you don't want to do
> it yourself I'll add it to my ever growing todo list.
> 

Sure, I'm up for this. The bvec-related items are the next logical part
of the gup/dma conversions to work on, and I just wanted to avoid solving the
same problem if you were already in the code.


>> Or on the put_user_bvec() idea?
> 
> I have a prototype from two month ago:
> 
> http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/gup-bvec
> 
> but that only survived the most basic testing, so it'll need more work,
> which I'm not sure when I'll find time for.
> 

I'll take a peek, and probably pester you with a few questions if I get
confused. :)

thanks,
-- 
John Hubbard
NVIDIA