linux-kernel - Re: [PATCH RESEND v6 5/9] mm: Introduce mf_dax_kill

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Date:   Thu, 5 Aug 2021 17:59:01 -0700
From:   Jane Chu <jane.chu@...cle.com>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        nvdimm@...ts.linux.dev, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, dm-devel@...hat.com
Cc:     djwong@...nel.org, dan.j.williams@...el.com, david@...morbit.com,
        hch@....de, agk@...hat.com, snitzer@...hat.com
Subject: Re: [PATCH RESEND v6 5/9] mm: Introduce mf_dax_kill_procs() for fsdax
 case

> @@ -134,6 +134,12 @@ static int hwpoison_filter_dev(struct page *p)
>   	if (PageSlab(p))
>   		return -EINVAL;
>   
> +	if (pfn_valid(page_to_pfn(p))) {
> +		if (is_device_fsdax_page(p))
> +			return 0;
> +	} else
> +		return -EINVAL;
> +

Just curious, what is the rational for preventing dax pages from
participating in hwpoison_filter test?

> +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, int flags)
> +{
> +	LIST_HEAD(to_kill);
> +	/* load the pfn of the dax mapping file */
> +	unsigned long pfn = dax_load_pfn(mapping, index);
> +
> +	/* the failure pfn may not actually be mmapped, so no need to
> +	 * unmap and kill procs */
> +	if (!pfn)
> +		return 0;

what if a process has mapped the file but never faulted in, but did ask
for early signal, will it be excluded due to lack of the 'pfn' association?

thanks,
-jane