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

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Date:   Sun, 6 Mar 2022 05:21:11 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Matthew Wilcox <willy@...radead.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 02:57:55AM +0000, Matthew Wilcox wrote:
> 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.

f_ops->mmap() would require an additional parameter, which results
heavy refactoring.

struct file_operations has 1125 references in the kernel tree, so I
decided to check this way around first. 

BR, Jarkko