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ARM: ZERO_PAGE: Avoid flush_dcache_page() for zero page 

The zero page is read-only, and has its cache state cleared during
boot.  No further maintanence for this page is required.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2009-10-25 10:23:04 +00:00
parent b7dc0b2cfc
commit 421fe93cc4
3 changed files with 18 additions and 2 deletions
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7
arch/arm/mm/fault-armv.c
View File

@ -151,7 +151,14 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
if (!pfn_valid(pfn))
return;
/*
* The zero page is never written to, so never has any dirty
* cache lines, and therefore never needs to be flushed.
*/
page = pfn_to_page(pfn);
if (page == ZERO_PAGE(0))
return;
mapping = page_mapping(page);
#ifndef CONFIG_SMP
if (test_and_clear_bit(PG_dcache_dirty, &page->flags))

11
arch/arm/mm/flush.c
View File

@ -189,7 +189,16 @@ static void __flush_dcache_aliases(struct address_space *mapping, struct page *p
*/
void flush_dcache_page(struct page *page)
{
struct address_space *mapping = page_mapping(page);
struct address_space *mapping;
/*
* The zero page is never written to, so never has any dirty
* cache lines, and therefore never needs to be flushed.
*/
if (page == ZERO_PAGE(0))
return;
mapping = page_mapping(page);
#ifndef CONFIG_SMP
if (!PageHighMem(page) && mapping && !mapping_mapped(mapping))

2
arch/arm/mm/mmu.c
View File

@ -1036,7 +1036,7 @@ void __init paging_init(struct machine_desc *mdesc)
*/
zero_page = alloc_bootmem_low_pages(PAGE_SIZE);
empty_zero_page = virt_to_page(zero_page);
flush_dcache_page(empty_zero_page);
__flush_dcache_page(NULL, empty_zero_page);
}
/*