linux-kernel - Re: [PATCH] kernel/kcov: Replace vm_insert_page with vmf_insert

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Date:   Sat, 22 Sep 2018 07:22:41 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Souptick Joarder <jrdr.linux@...il.com>
Cc:     akpm@...ux-foundation.org, mark.rutland@....com,
        aryabinin@...tuozzo.com, dvyukov@...gle.com, tglx@...utronix.de,
        gregkh@...uxfoundation.org, tchibo@...gle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/kcov: Replace vm_insert_page with vmf_insert_page

On Fri, Sep 21, 2018 at 12:42:54AM +0530, Souptick Joarder wrote:
>  		for (off = 0; off < size; off += PAGE_SIZE) {
>  			page = vmalloc_to_page(kcov->area + off);
> -			if (vm_insert_page(vma, vma->vm_start + off, page))
> -				WARN_ONCE(1, "vm_insert_page() failed");
> +			if (vmf_insert_page(vma, vma->vm_start + off, page)
> +					!= VM_FAULT_NOPAGE)
> +				WARN_ONCE(1, "vmf_insert_page() failed");
>  		}

I think this is the wrong approach (as well as being buggy).

We should have a vmalloc_insert_range() _or something similar_ that
replaces this entire loop.  That makes each _user_ simpler.  What you're
trying to do right now makes each user more complex, and that's the
wrong approach.