linux-kernel - Re: [PATCH v3 05/11] mm, fsdax: Refactor memory-failure handler for dax mapping

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Date:   Wed, 10 Feb 2021 14:33:47 +0100
From:   Christoph Hellwig <hch@....de>
To:     Shiyang Ruan <ruansy.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, dm-devel@...hat.com,
        darrick.wong@...cle.com, dan.j.williams@...el.com,
        david@...morbit.com, hch@....de, agk@...hat.com,
        snitzer@...hat.com, rgoldwyn@...e.de, qi.fuli@...itsu.com,
        y-goto@...itsu.com
Subject: Re: [PATCH v3 05/11] mm, fsdax: Refactor memory-failure handler
 for dax mapping

> +extern int mf_dax_mapping_kill_procs(struct address_space *mapping, pgoff_t index, int flags);

No nee for the extern, please avoid the overly long line.

> @@ -120,6 +121,13 @@ 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;
> +	}
> +

This looks odd.  For one there is no need for an else after a return.
But more importantly page_mapping() as called below pretty much assumes
a valid PFN, so something is fishy in this function.

> +	if (is_zone_device_page(p)) {
> +		if (is_device_fsdax_page(p))
> +			tk->addr = vma->vm_start +
> +					((pgoff - vma->vm_pgoff) << PAGE_SHIFT);

The arithmetics here scream for a common helper, I suspect there might
be other places that could use the same helper.

> +int mf_dax_mapping_kill_procs(struct address_space *mapping, pgoff_t index, int flags)

Overly long line.  Also the naming scheme with the mf_ seems rather
unusual. Maybe dax_kill_mapping_procs?  Also please add a kerneldoc
comment describing the function given that it exported.