[PATCH 1/3] ARM: Assume new page cache pages have dirty D-cache
Catalin Marinas
catalin.marinas at arm.com
Mon Jun 28 12:49:48 EDT 2010
On Mon, 2010-06-28 at 15:22 +0100, Rabin Vincent wrote:
> On Fri, Jun 25, 2010 at 01:01:32PM +0100, Catalin Marinas wrote:
> > @@ -508,6 +508,12 @@ void ___dma_page_dev_to_cpu(struct page *page, unsigned long off,
> > outer_inv_range(paddr, paddr + size);
> >
> > dma_cache_maint_page(page, off, size, dir, dmac_unmap_area);
> > +
> > + /*
> > + * Mark the D-cache clean for this page to avoid extra flushing.
> > + */
> > + if (dir != DMA_TO_DEVICE)
> > + set_bit(PG_dcache_clean, &page->flags);
>
> off + size does not necessarily cover the full page. We probably
> shouldn't be setting it as clean unless it does?
Good point. See below for an updated patch.
> Also, off + size can cover multiple physically contiguous pages, so
> perhaps they too can be set as clean if they're fully covered.
While it may be possible, I don't think that's common. I would only care
about the "page" argument, otherwise you have to do some conversion to
find the page structure and it may not be worth.
ARM: Assume new page cache pages have dirty D-cache
From: Catalin Marinas <catalin.marinas at arm.com>
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().
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
Cc: Rabin Vincent <rabin.vincent at stericsson.com>
---
arch/arm/include/asm/cacheflush.h | 6 +++---
arch/arm/include/asm/tlbflush.h | 2 +-
arch/arm/mm/copypage-v4mc.c | 2 +-
arch/arm/mm/copypage-v6.c | 2 +-
arch/arm/mm/copypage-xscale.c | 2 +-
arch/arm/mm/dma-mapping.c | 6 ++++++
arch/arm/mm/fault-armv.c | 4 ++--
arch/arm/mm/flush.c | 3 ++-
8 files changed, 17 insertions(+), 10 deletions(-)
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index 4656a24..d3730f0 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -137,10 +137,10 @@
#endif
/*
- * This flag is used to indicate that the page pointed to by a pte
- * is dirty and requires cleaning before returning it to the user.
+ * This flag is used to indicate that the page pointed to by a pte is clean
+ * and does not require cleaning before returning it to the user.
*/
-#define PG_dcache_dirty PG_arch_1
+#define PG_dcache_clean PG_arch_1
/*
* MM Cache Management
diff --git a/arch/arm/include/asm/tlbflush.h b/arch/arm/include/asm/tlbflush.h
index bd863d8..40a7092 100644
--- a/arch/arm/include/asm/tlbflush.h
+++ b/arch/arm/include/asm/tlbflush.h
@@ -552,7 +552,7 @@ extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);
#endif
/*
- * if PG_dcache_dirty is set for the page, we need to ensure that any
+ * If PG_dcache_clean is not set for the page, we need to ensure that any
* cache entries for the kernels virtual memory range are written
* back to the page.
*/
diff --git a/arch/arm/mm/copypage-v4mc.c b/arch/arm/mm/copypage-v4mc.c
index 598c51a..b806151 100644
--- a/arch/arm/mm/copypage-v4mc.c
+++ b/arch/arm/mm/copypage-v4mc.c
@@ -73,7 +73,7 @@ void v4_mc_copy_user_highpage(struct page *to, struct page *from,
{
void *kto = kmap_atomic(to, KM_USER1);
- if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
+ if (!test_and_set_bit(PG_dcache_clean, &from->flags))
__flush_dcache_page(page_mapping(from), from);
spin_lock(&minicache_lock);
diff --git a/arch/arm/mm/copypage-v6.c b/arch/arm/mm/copypage-v6.c
index f55fa10..bdba6c6 100644
--- a/arch/arm/mm/copypage-v6.c
+++ b/arch/arm/mm/copypage-v6.c
@@ -79,7 +79,7 @@ static void v6_copy_user_highpage_aliasing(struct page *to,
unsigned int offset = CACHE_COLOUR(vaddr);
unsigned long kfrom, kto;
- if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
+ if (!test_and_set_bit(PG_dcache_clean, &from->flags))
__flush_dcache_page(page_mapping(from), from);
/* FIXME: not highmem safe */
diff --git a/arch/arm/mm/copypage-xscale.c b/arch/arm/mm/copypage-xscale.c
index 9920c0a..649bbcd 100644
--- a/arch/arm/mm/copypage-xscale.c
+++ b/arch/arm/mm/copypage-xscale.c
@@ -95,7 +95,7 @@ void xscale_mc_copy_user_highpage(struct page *to, struct page *from,
{
void *kto = kmap_atomic(to, KM_USER1);
- if (test_and_clear_bit(PG_dcache_dirty, &from->flags))
+ if (!test_and_set_bit(PG_dcache_clean, &from->flags))
__flush_dcache_page(page_mapping(from), from);
spin_lock(&minicache_lock);
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 9e7742f..fa3d07d 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -508,6 +508,12 @@ void ___dma_page_dev_to_cpu(struct page *page, unsigned long off,
outer_inv_range(paddr, paddr + size);
dma_cache_maint_page(page, off, size, dir, dmac_unmap_area);
+
+ /*
+ * Mark the D-cache clean for this page to avoid extra flushing.
+ */
+ if (dir != DMA_TO_DEVICE && off == 0 && size >= PAGE_SIZE)
+ set_bit(PG_dcache_clean, &page->flags);
}
EXPORT_SYMBOL(___dma_page_dev_to_cpu);
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index 9b906de..58846cb 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c
@@ -141,7 +141,7 @@ make_coherent(struct address_space *mapping, struct vm_area_struct *vma,
* a page table, or changing an existing PTE. Basically, there are two
* things that we need to take care of:
*
- * 1. If PG_dcache_dirty is set for the page, we need to ensure
+ * 1. If PG_dcache_clean is not set for the page, we need to ensure
* that any cache entries for the kernels virtual memory
* range are written back to the page.
* 2. If we have multiple shared mappings of the same space in
@@ -169,7 +169,7 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr,
mapping = page_mapping(page);
#ifndef CONFIG_SMP
- if (test_and_clear_bit(PG_dcache_dirty, &page->flags))
+ if (!test_and_set_bit(PG_dcache_clean, &page->flags))
__flush_dcache_page(mapping, page);
#endif
if (mapping) {
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index c6844cb..9f9919b 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -248,7 +248,7 @@ void flush_dcache_page(struct page *page)
#ifndef CONFIG_SMP
if (!PageHighMem(page) && mapping && !mapping_mapped(mapping))
- set_bit(PG_dcache_dirty, &page->flags);
+ clear_bit(PG_dcache_clean, &page->flags);
else
#endif
{
@@ -257,6 +257,7 @@ void flush_dcache_page(struct page *page)
__flush_dcache_aliases(mapping, page);
else if (mapping)
__flush_icache_all();
+ set_bit(PG_dcache_clean, &page->flags);
}
}
EXPORT_SYMBOL(flush_dcache_page);
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