Re: [PATCH v41 10/24] mm: Add 'mprotect' hook to struct vm_operations_struct

[Matthew Wilcox]

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.