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

From: Russell King - ARM Linux
Date: Thu Mar 04 2010 - 11:44:36 EST

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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