fuse: use clear_highpage() and KM_USER0 instead of KM_USER1

Commit 7909b1c640 ("fuse: don't use atomic kmap") removed KM_USER0 usage
from fuse/dev.c.  Switch KM_USER1 uses to KM_USER0 for clarity.  Also
replace open coded clear_highpage().

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fuse/dev.c

@@ -809,11 +809,9 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
 	int err;
 	struct page *page = *pagep;
 
-	if (page && zeroing && count < PAGE_SIZE) {
-		void *mapaddr = kmap_atomic(page, KM_USER1);
-		clear_page(mapaddr);
-		kunmap_atomic(mapaddr, KM_USER1);
-	}
+	if (page && zeroing && count < PAGE_SIZE)
+		clear_highpage(page);
+
 	while (count) {
 		if (cs->write && cs->pipebufs && page) {
 			return fuse_ref_page(cs, page, offset, count);
@@ -830,10 +828,10 @@ static int fuse_copy_page(struct fuse_copy_state *cs, struct page **pagep,
 			}
 		}
 		if (page) {
-			void *mapaddr = kmap_atomic(page, KM_USER1);
+			void *mapaddr = kmap_atomic(page, KM_USER0);
 			void *buf = mapaddr + offset;
 			offset += fuse_copy_do(cs, &buf, &count);
-			kunmap_atomic(mapaddr, KM_USER1);
+			kunmap_atomic(mapaddr, KM_USER0);
 		} else
 			offset += fuse_copy_do(cs, NULL, &count);
 	}