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Date:   Sun, 6 Mar 2022 02:57:55 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Nathaniel McCallum <nathaniel@profian.com>,
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        linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
        dri-devel@lists.freedesktop.org, codalist@coda.cs.cmu.edu,
        linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH RFC] mm: Add f_ops->populate()
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References: <20220306021534.83553-1-jarkko@kernel.org>
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On Sun, Mar 06, 2022 at 04:15:33AM +0200, Jarkko Sakkinen wrote:
> Sometimes you might want to use MAP_POPULATE to ask a device driver to
> initialize the device memory in some specific manner. SGX driver can use
> this to request more memory by issuing ENCLS[EAUG] x86 opcode for each
> page in the address range.
> 
> Add f_ops->populate() with the same parameters as f_ops->mmap() and make
> it conditionally called inside call_mmap(). Update call sites
> accodingly.

Your device driver has a ->mmap operation.  Why does it need another
one?  More explanation required here.