做项目要修改blktap中block-sync.c 的 tdsync_queue_write函数
在用write向镜像写入自己新分配的buffer数据时报错 errno 为22
参考write函数错误号发现
EINVAL fd is attached to an object which is unsuitable for writing; or the file was opened with the O_DIRECT flag, and either the address specified in buf, the value specified incount, or the current file offset is not suitably aligned.
比较原有buf变量内存地址发现其内存对其大小为4096字节 而自己使用Malloc默认采用8字节
改用 memalign(4096,size) 分配内存 写入buffer成功
环境：openSUSE 12.1 X86_64 XEN 4.1.2 DomU:openSUSE 12.1(PV)
p.s 后来经测试，由于原始磁盘镜像每个扇区为512字节，内存对齐512即可
