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Date:   Tue, 23 Jul 2019 17:36:40 +0200
From:   Christoph Hellwig <hch@lst.de>
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>,
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        Magnus Karlsson <magnus.karlsson@intel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Ming Lei <ming.lei@redhat.com>, Sage Weil <sage@redhat.com>,
        Santosh Shilimkar <santosh.shilimkar@oracle.com>,
        Yan Zheng <zyan@redhat.com>, netdev@vger.kernel.org,
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        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] mm/gup: introduce __put_user_pages()
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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.