Re: [PATCH] mm/gup: Use put_user_page*() instead of put_page*()

From: Bharath Vedartham <linux.bhar@gmail.com>
To: John Hubbard <jhubbard@nvidia.com>
Cc: akpm@linux-foundation.org, ira.weiny@intel.com,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Dimitri Sivanich" <sivanich@sgi.com>,
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	xdp-newbies@vger.kernel.org, "Jason Gunthorpe" <jgg@ziepe.ca>
Subject: Re: [PATCH] mm/gup: Use put_user_page*() instead of put_page*()
Date: Tue, 16 Jul 2019 01:06:38 +0530	[thread overview]
Message-ID: <20190715193638.GC21161@bharath12345-Inspiron-5559> (raw)
In-Reply-To: <1aeb21d9-6dc6-c7d2-58b6-279b1dfc523b@nvidia.com>

On Mon, Jul 15, 2019 at 11:10:20AM -0700, John Hubbard wrote:
> On 7/14/19 11:56 PM, Bharath Vedartham wrote:
> > On Sun, Jul 14, 2019 at 04:33:42PM -0700, John Hubbard wrote:
> >> On 7/14/19 12:08 PM, Bharath Vedartham wrote:
> [...]
> >> 1. Pull down https://github.com/johnhubbard/linux/commits/gup_dma_core
> >> and find missing conversions: look for any additional missing 
> >> get_user_pages/put_page conversions. You've already found a couple missing 
> >> ones. I haven't re-run a search in a long time, so there's probably even more.
> >> 	a) And find more, after I rebase to 5.3-rc1: people probably are adding
> >> 	get_user_pages() calls as we speak. :)
> > Shouldn't this be documented then? I don't see any docs for using
> > put_user_page*() in v5.2.1 in the memory management API section?
> 
> Yes, it needs documentation. My first try (which is still in the above git
> repo) was reviewed and found badly wanting, so I'm going to rewrite it. Meanwhile,
> I agree that an interim note would be helpful, let me put something together.
> 
> [...]
> >>     https://github.com/johnhubbard/linux/commits/gup_dma_core
> >>
> >>     a) gets rebased often, and
> >>
> >>     b) has a bunch of commits (iov_iter and related) that conflict
> >>        with the latest linux.git,
> >>
> >>     c) has some bugs in the bio area, that I'm fixing, so I don't trust
> >>        that's it's safely runnable, for a few more days.
> > I assume your repo contains only work related to fixing gup issues and
> > not the main repo for gup development? i.e where gup changes are merged?
> 
> Correct, this is just a private tree, not a maintainer tree. But I'll try to
> keep the gup_dma_core branch something that is usable by others, during the
> transition over to put_user_page(), because the page-tracking patches are the
> main way to test any put_user_page() conversions.
> 
> As Ira said, we're using linux-mm as the real (maintainer) tree.
Thanks for the info! 
> 
> thanks,
> -- 
> John Hubbard
> NVIDIA