[Devel] [PATCH VZ9 06/20] fuse: better check_zero

[Alexey Kuznetsov]

This version of check_zero is the same on non-zero areas,
but ~2 times faster on zero areas. Though benchmark was
done in userspace, memcmp may be different there

It is strange. Linux should provide a good function doing this.
Did I miss it?

Signed-off-by: Alexey Kuznetsov <kuznet at acronis.com>
---
 fs/fuse/kio/pcs/pcs_cs_accel.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/fuse/kio/pcs/pcs_cs_accel.c b/fs/fuse/kio/pcs/pcs_cs_accel.c
index a76f28e..fc6a35f 100644
--- a/fs/fuse/kio/pcs/pcs_cs_accel.c
+++ b/fs/fuse/kio/pcs/pcs_cs_accel.c
@@ -278,13 +278,10 @@ static int verify_crc(struct pcs_int_request * ireq, u32 * crc)
 static int check_zero(struct page * page, unsigned int offset)
 {
 	u64 * addr = kmap(page) + offset;
-	int i;
 
-	for (i = 0; i < 512/8; i++) {
-		if (likely(addr[i] != 0)) {
-			kunmap(page);
-			return 0;
-		}
+        if (likely(addr[0] || memcmp(addr, addr + 1, 512 - 8))) {
+		kunmap(page);
+                return 0;
 	}
 	kunmap(page);
 	return 1;
-- 
1.8.3.1