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Date:   Sun, 15 Nov 2020 17:32:08 +0000
From:   Matthew Wilcox <willy@infradead.org>
To:     Jarkko Sakkinen <jarkko@kernel.org>
Cc:     x86@kernel.org, linux-sgx@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
        Mel Gorman <mgorman@techsingularity.net>,
        Jethro Beekman <jethro@fortanix.com>,
        Dave Hansen <dave.hansen@intel.com>,
        andriy.shevchenko@linux.intel.com, asapek@google.com, bp@alien8.de,
        cedric.xing@intel.com, chenalexchen@google.com,
        conradparker@google.com, cyhanish@google.com,
        haitao.huang@intel.com, kai.huang@intel.com, kai.svahn@intel.com,
        kmoy@google.com, ludloff@google.com, luto@kernel.org,
        nhorman@redhat.com, npmccallum@redhat.com, puiterwijk@redhat.com,
        rientjes@google.com, tglx@linutronix.de, yaozhangx@google.com,
        mikko.ylinen@intel.com
Subject: Re: [PATCH v41 10/24] mm: Add 'mprotect' hook to struct
 vm_operations_struct
Message-ID: <20201115173208.GR17076@casper.infradead.org>
References: <20201112220135.165028-1-jarkko@kernel.org>
 <20201112220135.165028-11-jarkko@kernel.org>
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In-Reply-To: <20201112220135.165028-11-jarkko@kernel.org>
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On Fri, Nov 13, 2020 at 12:01:21AM +0200, Jarkko Sakkinen wrote:
> +++ b/include/linux/mm.h
> @@ -559,6 +559,13 @@ struct vm_operations_struct {
>  	void (*close)(struct vm_area_struct * area);
>  	int (*split)(struct vm_area_struct * area, unsigned long addr);
>  	int (*mremap)(struct vm_area_struct * area);
> +	/*
> +	 * Called by mprotect() to make driver-specific permission
> +	 * checks before mprotect() is finalised.   The VMA must not
> +	 * be modified.  Returns 0 if eprotect() can proceed.
> +	 */

This is the wrong place for this documentation, and it's absurdly
specific to your implementation.  It should be in
Documentation/filesystems/locking.rst.

> +	int (*mprotect)(struct vm_area_struct *vma, unsigned long start,
> +			unsigned long end, unsigned long newflags);
> +
> +		if (vma->vm_ops && vma->vm_ops->mprotect)
> +			error = vma->vm_ops->mprotect(vma, nstart, tmp, newflags);
> +		if (error)
> +			goto out;
> +
>  		error = mprotect_fixup(vma, &prev, nstart, tmp, newflags);
>  		if (error)
>  			goto out;
> +
>  		nstart = tmp;

Spurious newline added.