btrfs: use btrfs_crc32c{,_final}() in for free space cache

The CRC checksum in the free space cache is not dependant on the super
block's csum_type field but always a CRC32C.

So use btrfs_crc32c() and btrfs_crc32c_final() instead of
btrfs_csum_data() and btrfs_csum_final() for computing these checksums.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/free-space-cache.c

@@ -465,9 +465,8 @@ static void io_ctl_set_crc(struct btrfs_io_ctl *io_ctl, int index)
 	if (index == 0)
 		offset = sizeof(u32) * io_ctl->num_pages;
 
-	crc = btrfs_csum_data(io_ctl->orig + offset, crc,
-			      PAGE_SIZE - offset);
-	btrfs_csum_final(crc, (u8 *)&crc);
+	crc = btrfs_crc32c(crc, io_ctl->orig + offset, PAGE_SIZE - offset);
+	btrfs_crc32c_final(crc, (u8 *)&crc);
 	io_ctl_unmap_page(io_ctl);
 	tmp = page_address(io_ctl->pages[0]);
 	tmp += index;
@@ -493,9 +492,8 @@ static int io_ctl_check_crc(struct btrfs_io_ctl *io_ctl, int index)
 	val = *tmp;
 
 	io_ctl_map_page(io_ctl, 0);
-	crc = btrfs_csum_data(io_ctl->orig + offset, crc,
-			      PAGE_SIZE - offset);
-	btrfs_csum_final(crc, (u8 *)&crc);
+	crc = btrfs_crc32c(crc, io_ctl->orig + offset, PAGE_SIZE - offset);
+	btrfs_crc32c_final(crc, (u8 *)&crc);
 	if (val != crc) {
 		btrfs_err_rl(io_ctl->fs_info,
 			"csum mismatch on free space cache");