crypto: scatterwalk - Hide PageSlab call to optimise away flush_dcach…

…e_page On architectures where flush_dcache_page is not needed, we will end up generating all the code up to the PageSlab call. This is because PageSlab operates on a volatile pointer and thus cannot be optimised away. This patch works around this by checking whether flush_dcache_page is needed before we call PageSlab which then allows PageSlab to be compiled awy. Signed-off-by: Herbert Xu <[email protected]>
kyagi · Jun 3, 2015 · 1605440 · 1605440
1 parent b7c89d9
commit 1605440
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
@@ -54,7 +54,11 @@ static void scatterwalk_pagedone(struct scatter_walk *walk, int out,
 		struct page *page;
 
 		page = sg_page(walk->sg) + ((walk->offset - 1) >> PAGE_SHIFT);
-		if (!PageSlab(page))
+		/* Test ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE first as
+		 * PageSlab cannot be optimised away per se due to
+		 * use of volatile pointer.
+		 */
+		if (ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE && !PageSlab(page))
 			flush_dcache_page(page);
 	}