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Date:   Thu, 15 Aug 2019 23:47:53 -0700
From:   Christoph Hellwig <hch@infradead.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Dave Chinner <david@fromorbit.com>,
        xfs <linux-xfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        fdmanana@gmail.com, gaoxiang25@huawei.com
Subject: Re: [PATCH v4] vfs: fix page locking deadlocks when deduping files
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References: <20190815164940.GA15198@magnolia>
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On Thu, Aug 15, 2019 at 11:18:04AM -0700, Matthew Wilcox wrote:
> But I don't think read_mapping_page() can return a page which doesn't have
> PageUptodate set.  Follow the path down through read_cache_page() into
> do_read_cache_page().

read_mapping_page() can't, but I think we need the check after the 
lock_page still.