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>
diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c
index d0d17b6..4fbc7de 100644
--- a/arch/arm/mm/fault-armv.c
+++ b/arch/arm/mm/fault-armv.c
@@ -151,7 +151,14 @@
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))
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 43474d8..82f4b06 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -189,7 +189,16 @@
*/
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))
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index ea67be0..2427cdc 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1036,7 +1036,7 @@
*/
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);
}
/*