linux-kernel - Re: [PATCH RFC] mm: Add f

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Message-ID: <YiQjM7LdwoAWpC5L@casper.infradead.org>
Date:   Sun, 6 Mar 2022 02:57:55 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Nathaniel McCallum <nathaniel@...fian.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        linux-sgx@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, codalist@...a.cs.cmu.edu,
        linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH RFC] mm: Add f_ops->populate()

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.