This helps prevent stalls, especially while the snapshot cleaner is
running hard
Signed-off-by: Chris Mason <chris.mason@oracle.com>
        level = btrfs_header_level(buf);
        nritems = btrfs_header_nritems(buf);
        for (i = 0; i < nritems; i++) {
+               cond_resched();
                if (level == 0) {
                        u64 disk_bytenr;
                        btrfs_item_key_to_cpu(buf, &key, i);
 
        for (i = 0; i < nritems; i++) {
                u64 disk_bytenr;
+               cond_resched();
 
                btrfs_item_key_to_cpu(leaf, &key, i);
                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)