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Commit 421fe93c authored by Russell King's avatar Russell King
Browse files

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: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent b7dc0b2c

arch/arm/mm/fault-armv.c

+7 −0
Original line number Diff line number Diff line
@@ -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))

arch/arm/mm/flush.c

+10 −1
Original line number Diff line number Diff line
@@ -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))

arch/arm/mm/mmu.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

}



/*