linux-kernel - Re: [PATCH] mm: Remove usages of ACCESS

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Message-ID: <551177F0.3070006@de.ibm.com>
Date:	Tue, 24 Mar 2015 15:42:56 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Jason Low <jason.low2@...com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
CC:	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Christoph Lameter <cl@...ux.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Aswin Chandramouleeswaran <aswin@...com>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH] mm: Remove usages of ACCESS_ONCE

Am 23.03.2015 um 23:44 schrieb Jason Low:
> Commit 38c5ce936a08 converted ACCESS_ONCE usage in gup_pmd_range() to
> READ_ONCE, since ACCESS_ONCE doesn't work reliably on non-scalar types.
> 
> This patch removes the rest of the usages of ACCESS_ONCE, and use
> READ_ONCE for the read accesses. This also makes things cleaner,
> instead of using separate/multiple sets of APIs.
> 
> Signed-off-by: Jason Low <jason.low2@...com>

Reviewed-by: Christian Borntraeger <borntraeger@...ibm.com>

one remark or question:

> -	anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
> +	anon_mapping = (unsigned long)READ_ONCE(page->mapping);

Were the white space changes intentional? IIRC checkpatch does prefer
it your way and you have changed several places - so I assume yes.
Either way, its probably fine to change that along.

Christian

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