From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/3] mm/gup: introduce __put_user_pages()
Date: Tue, 23 Jul 2019 17:36:40 +0200
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References: <20190722223415.13269-1-jhubbard@nvidia.com> <20190722223415.13269-2-jhubbard@nvidia.com> <20190723055359.GC17148@lst.de> <8ab4899c-ec12-a713-cac2-d951fff2a347@nvidia.com>
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To: John Hubbard <jhubbard@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>, john.hubbard@gmail.com, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= <bjorn.topel@intel.com>, Boaz Harrosh <boaz@plexistor.com>, 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>, =?iso-8859-1?B?Suly9G1l?= Glisse <jglisse@redhat.com>, Johannes Thumshirn <jthumshirn@suse.de>, Magnus Karlsson <magnus.karlsson@intel.com>, Matthew Wilcox <willy@infradead.org>, Miklos Szeredi <miklos@szeredi.hu>, Ming
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On Mon, Jul 22, 2019 at 11:33:32PM -0700, John Hubbard wrote:
> I'm seeing about 18 places where set_page_dirty() is used, in the call site
> conversions so far, and about 20 places where set_page_dirty_lock() is
> used. So without knowing how many of the former (if any) represent bugs,
> you can see why the proposal here supports both DIRTY and DIRTY_LOCK.

Well, it should be fairly easy to audit.  set_page_dirty() is only
safe if we are dealing with a file backed page where we have reference
on the inode it hangs off.  Which should basically be never or almost
never.