void (*writeseg)(struct super_block *sb, u64 ofs, size_t len);
int (*erase)(struct super_block *sb, loff_t ofs, size_t len,
int ensure_write);
void (*writeseg)(struct super_block *sb, u64 ofs, size_t len);
int (*erase)(struct super_block *sb, loff_t ofs, size_t len,
int ensure_write);