linux-kernel - Re: [PATCH] ARM:mm: fix kmap_atomic_to

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Message-ID: <5510159.Ge1KiGjbaB@wuerfel>
Date:	Tue, 13 Oct 2015 13:44:09 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Jongsung Kim <neidhard.kim@....com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Gunho Lee <gunho.lee@....com>, Chanho Min <chanho.min@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM:mm: fix kmap_atomic_to_page

On Tuesday 13 October 2015 11:06:44 Jongsung Kim wrote:
> On 10/12/2015 06:27 PM, Arnd Bergmann wrote:
> > How about changing the zcomp code to pass the page pointer instead of the kernel space pointer? That would avoid having to do the kmap_atomic, which can itself be expensive on 32-bit machines and should not be needed here if you have a HW DMA engine doing the compression. Arnd 
> 
> Mainline zram uses lzo / lz4 library functions as backend. Using kmap_atomic and passing address look reasonable.

Yes, I know, but changing this to do the kmap_atomic in the backend
seems better here if you are adding another backend that doesn't
want or need the kmap_atomic.

	Arnd
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