From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH 3/3] net/xdp: convert put_page() to put_user_page*()
Date: Tue, 23 Jul 2019 16:24:23 -0700
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To: Ira Weiny <ira.weiny@intel.com>
Cc: john.hubbard@gmail.com, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>, Boaz Harrosh <boaz@plexistor.com>, Christoph Hellwig <hch@lst.de>, Daniel Vetter <daniel@ffwll.ch>, Dan Williams <dan.j.williams@intel.com>, Dave Chinner <david@fromorbit.com>, David Airlie <airlied@linux.ie>, "David S . Miller" <davem@davemloft.net>, Ilya Dryomov <idryomov@gmail.com>, Jan Kara <jack@suse.cz>, Jason Gunthorpe <jgg@ziepe.ca>, Jens Axboe <axboe@kernel.dk>, =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>, Johannes Thumshirn <jthumshirn@suse.de>, Magnus Karlsson <magnus.karlsson@intel.com>, Matthew Wilcox <willy@infradead.org>, Miklos Szeredi <miklos@szeredi.hu>
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On 7/23/19 11:06 AM, Ira Weiny wrote:
> On Mon, Jul 22, 2019 at 09:41:34PM -0700, John Hubbard wrote:
>> On 7/22/19 5:25 PM, Ira Weiny wrote:
>>> On Mon, Jul 22, 2019 at 03:34:15PM -0700, john.hubbard@gmail.com wrote:
...
>> Obviously, this stuff is all subject to a certain amount of opinion, but I
>> think I'm on really solid ground as far as precedent goes. So I'm pushing
>> back on the NAK... :)
> 
> Fair enough...  However, we have discussed in the past how GUP can be a
> confusing interface to use.
> 
> So I'd like to see it be more directed.  Only using the __put_user_pages()
> version allows us to ID callers easier through a grep of PUP_FLAGS_DIRTY_LOCK
> in addition to directing users to use that interface rather than having to read
> the GUP code to figure out that the 2 calls above are equal.  It is not a huge
> deal but...
> 

OK, combining all the feedback to date, which is:

* the leading double underscore is unloved,

* set_page_dirty() is under investigation, but likely guilty of incitement
  to cause bugs,


...we end up with this:

void put_user_pages_dirty_lock(struct page **pages, unsigned long npages,
			       bool make_dirty)

...which I have a v2 patchset for, ready to send out. It makes IB all pretty 
too. :)


thanks,
-- 
John Hubbard
NVIDIA