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From: David Laight <David.Laight@ACULAB.COM>
To: 'Matthew Wilcox' <willy@infradead.org>,
	"brouer@redhat.com" <brouer@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	"linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
	"ilias.apalodimas@linaro.org" <ilias.apalodimas@linaro.org>,
	"mcroce@linux.microsoft.com" <mcroce@linux.microsoft.com>,
	"grygorii.strashko@ti.com" <grygorii.strashko@ti.com>,
	"arnd@kernel.org" <arnd@kernel.org>, "hch@lst.de" <hch@lst.de>,
	"linux-snps-arc@lists.infradead.org"
	<linux-snps-arc@lists.infradead.org>,
	"mhocko@kernel.org" <mhocko@kernel.org>,
	"mgorman@suse.de" <mgorman@suse.de>
Subject: RE: [PATCH 1/2] mm: Fix struct page layout on 32-bit systems
Date: Sat, 17 Apr 2021 21:18:57 +0000
Message-ID: <386d009232dc42bdaf83d4cc36b13864@AcuMS.aculab.com> (raw)
In-Reply-To: <20210417024522.GP2531743@casper.infradead.org>

From: Matthew Wilcox <willy@infradead.org>
> Sent: 17 April 2021 03:45
> 
> Replacement patch to fix compiler warning.
...
>  static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
>  {
> -	return page->dma_addr;
> +	dma_addr_t ret = page->dma_addr[0];
> +	if (sizeof(dma_addr_t) > sizeof(unsigned long))
> +		ret |= (dma_addr_t)page->dma_addr[1] << 16 << 16;

Ugly as well.

Why not just replace the (dma_addr_t) cast with a (u64) one?
Looks better than the double shift.

Same could be done for the '>> 32'.
Is there an upper_32_bits() that could be used??

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


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Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-16 23:07 [PATCH 0/2] Change struct page layout for page_pool Matthew Wilcox (Oracle)
2021-04-16 23:07 ` [PATCH 1/2] mm: Fix struct page layout on 32-bit systems Matthew Wilcox (Oracle)
2021-04-17  1:08   ` kernel test robot
2021-04-17  2:45   ` Matthew Wilcox
2021-04-17 18:32     ` Ilias Apalodimas
2021-04-17 20:22       ` Matthew Wilcox
2021-04-18 11:21         ` Ilias Apalodimas
2021-04-17 21:18     ` David Laight [this message]
2021-04-17 22:45       ` Matthew Wilcox
2021-04-20  2:48     ` Vineet Gupta
2021-04-20  3:10       ` Matthew Wilcox
2021-04-20  7:07         ` Arnd Bergmann
2021-04-20 21:14           ` Vineet Gupta
2021-04-20 21:20             ` Arnd Bergmann
2021-04-21  5:50               ` hch
2021-04-21  8:43               ` David Laight
2021-04-21  8:58                 ` Arnd Bergmann
2021-04-20  7:39     ` Geert Uytterhoeven
2021-04-20  8:39       ` David Laight
2021-04-20 11:32       ` Matthew Wilcox
2021-04-17  7:34   ` Jesper Dangaard Brouer
2021-04-20  7:21   ` Rasmus Villemoes
2021-04-16 23:07 ` [PATCH 2/2] mm: Indicate pfmemalloc pages in compound_head Matthew Wilcox (Oracle)
2021-04-17 21:13   ` David Laight
2021-04-17 21:28     ` Matthew Wilcox
2021-04-20  4:03 ` [PATCH 0/2] Change struct page layout for page_pool Michael Ellerman

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