linux-kernel - Re: [RFC PATCH] ARM: Assume new page cache pages have dirty D-cache

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Message-ID: <20100304164416.GD13417@n2100.arm.linux.org.uk>
Date:	Thu, 4 Mar 2010 16:44:16 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [RFC PATCH] ARM: Assume new page cache pages have dirty D-cache

On Tue, Mar 02, 2010 at 05:34:29PM +0000, Catalin Marinas wrote:
> There are places in Linux where writes to newly allocated page cache
> pages happen without a subsequent call to flush_dcache_page() (several
> PIO drivers including USB HCD). This patch changes the meaning of
> PG_arch_1 to be PG_dcache_clean and always flush the D-cache for a newly
> mapped page in update_mmu_cache().
> 
> The patch also sets the PG_arch_1 bit in the DMA cache maintenance
> function to avoid additional cache flushing in update_mmu_cache().
...
>  arch/arm/include/asm/cacheflush.h |    6 +++---
>  arch/arm/mm/copypage-v6.c         |    2 +-
>  arch/arm/mm/dma-mapping.c         |    5 +++++
>  arch/arm/mm/fault-armv.c          |    2 +-
>  arch/arm/mm/flush.c               |    2 +-
>  5 files changed, 11 insertions(+), 6 deletions(-)

Could you please send for RFC a fuller patch which covers all places that
PG_dcache_dirty is used and/or mentioned?

$ grep PG_dcache_dirty arch/arm -r
arch/arm/mm/copypage-v6.c:      if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
arch/arm/mm/fault-armv.c: *  1. If PG_dcache_dirty is set for the page, we need to ensure
arch/arm/mm/fault-armv.c:       if (test_and_clear_bit(PG_dcache_dirty, &page->flags))
arch/arm/mm/flush.c:            set_bit(PG_dcache_dirty, &page->flags);
arch/arm/mm/copypage-v4mc.c:    if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
arch/arm/mm/copypage-xscale.c:  if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
arch/arm/include/asm/tlbflush.h: * if PG_dcache_dirty is set for the page, we need to ensure that any
arch/arm/include/asm/cacheflush.h:#define PG_dcache_dirty PG_arch_1
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