use clear_page()/copy_page() in favor of memset()/memcpy() on whole pages

After all that's what they are intended for.
Signed-off-by: NJan Beulich <jbeulich@novell.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/fuse/dev.c

@@ -811,7 +811,7 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
 
 	if (page && zeroing && count < PAGE_SIZE) {
 		void *mapaddr = kmap_atomic(page, KM_USER1);
-		memset(mapaddr, 0, PAGE_SIZE);
+		clear_page(mapaddr);
 		kunmap_atomic(mapaddr, KM_USER1);
 	}
 	while (count) {

kernel/kexec.c

@@ -816,7 +816,7 @@ static int kimage_load_normal_segment(struct kimage *image,
 
 		ptr = kmap(page);
 		/* Start with a clear page */
-		memset(ptr, 0, PAGE_SIZE);
+		clear_page(ptr);
 		ptr += maddr & ~PAGE_MASK;
 		mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);
 		if (mchunk > mbytes)

kernel/power/snapshot.c

@@ -993,7 +993,7 @@ static void copy_data_page(unsigned long dst_pfn, unsigned long src_pfn)
 			 */
 			safe_copy_page(buffer, s_page);
 			dst = kmap_atomic(d_page, KM_USER0);
-			memcpy(dst, buffer, PAGE_SIZE);
+			copy_page(dst, buffer);
 			kunmap_atomic(dst, KM_USER0);
 		} else {
 			safe_copy_page(page_address(d_page), s_page);
@@ -1687,7 +1687,7 @@ int snapshot_read_next(struct snapshot_handle *handle)
 		memory_bm_position_reset(&orig_bm);
 		memory_bm_position_reset(&copy_bm);
 	} else if (handle->cur <= nr_meta_pages) {
-		memset(buffer, 0, PAGE_SIZE);
+		clear_page(buffer);
 		pack_pfns(buffer, &orig_bm);
 	} else {
 		struct page *page;
@@ -1701,7 +1701,7 @@ int snapshot_read_next(struct snapshot_handle *handle)
 			void *kaddr;
 
 			kaddr = kmap_atomic(page, KM_USER0);
-			memcpy(buffer, kaddr, PAGE_SIZE);
+			copy_page(buffer, kaddr);
 			kunmap_atomic(kaddr, KM_USER0);
 			handle->buffer = buffer;
 		} else {
@@ -1984,7 +1984,7 @@ static void copy_last_highmem_page(void)
 		void *dst;
 
 		dst = kmap_atomic(last_highmem_page, KM_USER0);
-		memcpy(dst, buffer, PAGE_SIZE);
+		copy_page(dst, buffer);
 		kunmap_atomic(dst, KM_USER0);
 		last_highmem_page = NULL;
 	}
@@ -2270,9 +2270,9 @@ swap_two_pages_data(struct page *p1, struct page *p2, void *buf)
 
 	kaddr1 = kmap_atomic(p1, KM_USER0);
 	kaddr2 = kmap_atomic(p2, KM_USER1);
-	memcpy(buf, kaddr1, PAGE_SIZE);
-	memcpy(kaddr1, kaddr2, PAGE_SIZE);
-	memcpy(kaddr2, buf, PAGE_SIZE);
+	copy_page(buf, kaddr1);
+	copy_page(kaddr1, kaddr2);
+	copy_page(kaddr2, buf);
 	kunmap_atomic(kaddr2, KM_USER1);
 	kunmap_atomic(kaddr1, KM_USER0);
 }

kernel/power/swap.c

@@ -251,7 +251,7 @@ static int write_page(void *buf, sector_t offset, struct bio **bio_chain)
 	if (bio_chain) {
 		src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
 		if (src) {
-			memcpy(src, buf, PAGE_SIZE);
+			copy_page(src, buf);
 		} else {
 			WARN_ON_ONCE(1);
 			bio_chain = NULL;	/* Go synchronous */
@@ -325,7 +325,7 @@ static int swap_write_page(struct swap_map_handle *handle, void *buf,
 		error = write_page(handle->cur, handle->cur_swap, NULL);
 		if (error)
 			goto out;
-		memset(handle->cur, 0, PAGE_SIZE);
+		clear_page(handle->cur);
 		handle->cur_swap = offset;
 		handle->k = 0;
 	}
@@ -910,7 +910,7 @@ int swsusp_check(void)
 	hib_resume_bdev = open_by_devnum(swsusp_resume_device, FMODE_READ);
 	if (!IS_ERR(hib_resume_bdev)) {
 		set_blocksize(hib_resume_bdev, PAGE_SIZE);
-		memset(swsusp_header, 0, PAGE_SIZE);
+		clear_page(swsusp_header);
 		error = hib_bio_read_page(swsusp_resume_block,
 					swsusp_header, NULL);
 		if (error)

mm/memory.c

@@ -2080,7 +2080,7 @@ static inline void cow_user_page(struct page *dst, struct page *src, unsigned lo
 		 * zeroes.
 		 */
 		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE))
-			memset(kaddr, 0, PAGE_SIZE);
+			clear_page(kaddr);
 		kunmap_atomic(kaddr, KM_USER0);
 		flush_dcache_page(dst);
 	} else