29、 Implementation of xv6 file system (GDB tracks mkfs, buffer cache and log)

One 、 disk

boot block || sb(super block) block || log || inode block || free bit map || data block

boot block： Guide block

Two 、mkfs： Create file system

rsect/wsect（bread/bwrite）

balloc/bzero

ialloc

iappend

rinode/winode

1、 Through one buffer cache Keep a journal of inode

        bread/bwrite
||        buffer cache        ||
||        block array         ||

3、 ... and 、 Disk data write

The normal writing ：

1、log Write the log , Write all disk operations to the log

（1） Log header

（2） Data disk operation

（3） The end of the log

2、 Disk data write

3、 Release log

Break through and recover ：（ In the normal writing step , When a system error occurs , Restore data ）