VFS

很久以前有一种说法是，如果你希望学Unix，那么途径之一就是自己写一个Unix内核出来。这么多年以来，其实成功的人只有1个 :-)

不过，想要学习VFS这样的东西，只要写一个FS就可以了。在tmpfs上面跑了两个小时的stress2，系统还是活的很好，当然还有一些问题没有修完，但对VFS的锁的理解又加深了许多。

没啥技术含量，做个笔记而已。

相关日志如下：

Jan 11 22:19:02 tarsier postfix/postfix-script: stopping the Postfix mail system
Jan 11 22:19:02 tarsier postfix/master[92875]: terminating on signal 15
Jan 11 22:19:02 tarsier postfix/postfix-script: starting the Postfix mail system
Jan 11 22:19:02 tarsier postfix/master[70250]: daemon started – version 2.2.8, configuration /usr/local/etc/postfix

So he has finally (after about six or more months) imported read-only ResierFS, congratulations, dumbbell, you have made a quite impressive change!

Since 6-ism VFS interface is quite different from 5-ism, so this change is not likely to be merged IMO. Read-write is also not likely to be available soon, but anyway, ReiserFS is a nice FS and supporting it is a good move.

Today another GPL kernel has problem with a 4TB RAID5 array, it thought that it is 2.1TB (on boot) and refuse to initialize it with its native file systems, including ReiserFS. On contrary, FreeBSD 5.4 and 6.0 works smoothly with a GENERIC kernel. Oh well…

As title. We *need* to struggle to make the upcoming 6.0-RELEASE a good release . I hope we can show the great improvements taken place in 6-CURRENT and hopefully we can cut 6-STABLE this June.

Highlights on recent 6-CURRENT that was not merged (and may never be merged):

• MPSAFE VFS
• Integrated VFS hashing (generallized, traditionally it’s different on ufs, msdosfs, etc)
• 64bit-ize of several utilities, to ensure better usage of large storage.

有人一天改了一万一千多行代码。

有人一天改了一万一千多行VFS代码。

有人一天改了一万一千多行FreeBSD VFS代码。

我靠……

Matthew Dillon总是给人惊奇，这是一个你没办法不佩服的人。也许他的一些话让有的人感觉不爽，也许他被一些人误解，但他是Matthew Dillon。

I finally understood what he want, according to his post today:

" Hey, here’s an idea… using the VFS wrapper idea our
‘ports’ system could create a namespace that makes everything
appear to be preinstalled. So instead of CDing somewhere and
typing make, or running an apt-get type of utility, you would
simply run the program you want to run and our package manager
would download and install it on the fly."

I have just tried to umount /usr on my test box in order to get all outstanding writes to be sync’ed to disk (as Kirk McKusick said, the umount system call will do true sync of a file system).