Gentoo Taiwan 討論區

【Palatis】 wrote:最主要的原因是因為 reiser4 還不是很穩定, 甚至還沒被收進官方 kernel tree 中.

而且 Gentoo 是很自由的作業系統, 如果真的想用 reiser4, 可以考慮 (R)ecovery (I)s (P)ossible Rescue CD. (Google 找一下 RIP LiveCD).
除了光碟以外, 其他所有步驟都跟使用 Gentoo Official LiveCD 一模一樣.

如果希望 reiser4 能趕快被收錄進 official kernel repository, 請 "努力測試它!" 並且回報遇到的問題.

ina2588 wrote: 1.不穩定是指哪些問題呢.我英文很差.看了一堆文章.好處是說了一堆.那缺點呢?README和CHANGELOG好長一串阿.

2.RIP CD他是模擬gentooo的哪個版本阿.有人用過RR4的LIVE CD嗎?兩者之間能否說明一下差異性如何..一個救援用所以注重相容性.一個注重攜帶式桌面系統嗎?

抱怨:這個企鵝系統好麻煩阿.分的一堆分支.新手都被教學手冊淹沒了.讓我很難脫離4色旗子系統.又要忍受他天天催我買正版...嗚嗚...哭泣中...

ina2588 wrote:賤兔為何不內建reiserfs4呢?
這不是很多人很想要的東西嗎?
如果在安裝光碟裡植直接有支援.不是可以省下很多麻煩?
總是要替系統動2次手術.心中那個怨氣喔....

Reiser4 file semantics
Comment posted by Anonymous on Friday, August 27, 2004 - 09:31

In a nutshell every file now would look like a directory and can be opened as a directory. The names in that directory are not new files but meta data associated wit the file. This is well documented by Has Reiser on the Namesys site. This change is in some way sneaky, but in reality Hans has been writing about it for years - most of us did not pay too much attention. The immediate response in the community has been that this is too big a change and should be withdrawn.

[以下略]

From: Linus Torvalds [ email blocked ]
Subject: Re: silent semantic changes with reiser4
Date: 2004-08-29 21:50:07

[略]

Al, I think you should make the argument a bit more specific, because I
doubt a lot of people understand just what the problems are with aliased
names. Just a few examples of the problems involved will illuminate things
very well, I think. People who haven't been intimate with the name caches
probably simply don't understand why you worry so much.

I'll start out with some trivial examples, just to let Hans and others get
an idea about what the issues are. I think examples of problems are often
better ways to explain them than the abstract issues themselves.

Aliases: let's say that you have filename "a" hard-linked to filename "b",
and you have a directory structure of streams under there. So you have

a/file1
a/dir1/file2
a/dir2/file3

and (through the hard-link with "b") you have aliases of all these same
names available as "b/file1", "b/dir1/file2" etc).

Now, imagine that you have two processes doing

mv a/dir1 a/dir2/newdir

and

mv b/dir2 b/dir1/newdir

at the same time. Both of them MUST NOT SUCCEED, for pretty obvious
reasons (you'd have moved two directories within each other, and now
neither would be accessible any more).

How do you handle locking for this situation?

Another interesting case is what happens when you have looked up and cache
the filename "a/file1" and then another process does "rm b/file1". How do
Another interesting case is what happens when you have looked up and cache
the filename "a/file1" and then another process does "rm b/file1". How do
you update the _other_ cached copy, since they had two different names,
but _both_ names went away at the same time. Also again, how do you handle
locking?

The general VFS layer has a lot of rules, and avoids these problems by
simply never having aliases between two directories. If the same directory
shows up multiple times (which can happen with bind mounts), they have the
exact same dentry for the directory, it's just found through two different
vfsmount instances. That's why vfsmounts exist - they allow the same name
cache entry to show up in different places at the same time.

So when we do a bind mount, and the same directory shows up under two
different names "a" and "b", and we do a "rm b/file1", it _automatically_
disappears from "a/file1" too, simply by virtue of "a" and "b" literally
being the same dentry. No aliasing ever happens, and this makes coherency
and locking much easier (which is not to say that they are trivial, but
they are pretty damn clear in comparison to the alternatives).

What Al (and others) worries about is that the reiser4 name handling has
_none_ of these issues figured out and protected against. You can protect
against them by taking very heavy locks (you can trivially protect against
all races by taking one large lock around any operation), but the fact is,
that is just not an option for high-performance name lookup.

These aliasing/locking rules need to be global and wll-though-out. Not
just fix the two examples above, but be shown to be safe _in_general_.

Linus

From: http://www.linuxtoday.com/news_story.ph ... KN-SW-0001

Linux Today is not responsible for the content of the message below.
ac - Subject: Re: vfs ( Sep 1, 2004, 08:00:22 )

I think that is *precisly* what Linus
does *not* want to do.
.
I followed the thread a while and I read
that Linus wrote to Hans Reiser that Hans
should not have his "Reiser4" centric view of things.
.
Linux wasn't written to be a platform for the
distribution of ReiserFS. Sometimes if you listen
to Hans you get the impression that he thinks so.
ac

From: Linux: Merging Reiser4, How and Why?


From: Hans Reiser [email blocked]
Subject: Re: silent semantic changes with reiser4
Date: Thu, 26 Aug 2004 01:31:34 -0700

[略]
Andrew, we need to compete with WinFS and Dominic Giampaolo's filesystem for Apple, and that means we need to put search engine and database functionality into the filesystem. It takes 11 years of serious research to build a clean storage layer able to handle doing that. Reiser4 has done that, finally. None of the other Linux filesystems have. The next major release of ReiserFS is going to be bursting with semantic enhancements, because the prerequisites for them are in place now. None of the other Linux filesystems have those prerequisites. They won't be able to keep up with the semantic enhancements. This metafiles and file-directories stuff is actually fairly trivial stuff.
[略]


-------------------------------

From: Horst von Brand [email blocked]
Subject: Re: silent semantic changes with reiser4
Date: Thu, 26 Aug 2004 14:12:32 -0400

Hans Reiser [email blocked] said:
> Andrew Morton wrote:

[...]

> > The fact that one filesystem will offer features which other
> > filesystems do not and cannot offer makes me queasy for some reason.

Not me. As long as it is clearly experimental stuff that can be removed at
the head hacker's whim, that is. 2.7 material.

> Andrew, we need to compete with WinFS and Dominic Giampaolo's filesystem
> for Apple,

Says who?

> and that means we need to put search engine and database
> functionality into the filesystem.

Please don't. Unix works and is extremely popular because it _doesn't_ try
to be smart (policy vs mechanism distinction, simple abstractions that can
be combined endlessly). If you add this to the filesystems, you either redo
_all_ userland to understand _one_ particular way of doing "smart things"
(which will turn out to be almost exactly the dumbest possible for some
uses, and then you are stuck), or get lots of shards from broken apps (and
users, and sysadmins).


---------------------------

From: Linus Torvalds [email blocked]
Subject: Re: silent semantic changes with reiser4
Date: Fri, 27 Aug 2004 13:38:28 -0700 (PDT)

On Fri, 27 Aug 2004, Markus Törnqvist wrote:
>
> People will say it when people stop using Linux on servers because
> they can integrate metadata easier in other operating systems

Heh. Considering that WinFS seems to be delayed yet more, I don't think
that's a very strong argument.

Hell will freeze over before Microsoft does a filesystem right. Besides,
WinFS is likely almost in user mode anyway, ie mostly a library, rather
like the gnome people are already doing with nome storage.

So there's really no point in trying to push your agenda by trying to
scare people with MS activities. Linux kernel developers do what's right
because it is _right_, not because somebody else does it.

Linus

Yahoo!奇摩字典

semantics
n. (名詞 noun)

   1.
      【語】語義學
   2.
      【邏】語義論

ina2588 wrote:抱怨:這個企鵝系統好麻煩阿.分的一堆分支.新手都被教學手冊淹沒了.讓我很難脫離4色旗子系統.又要忍受他天天催我買正版...嗚嗚...哭泣中...

Reach wrote:

ina2588 wrote: 1.不穩定是指哪些問題呢.我英文很差.看了一堆文章.好處是說了一堆.那缺點呢?README和CHANGELOG好長一串阿.

嗯.. 不穩定喔 ...
　　我最初使用reiser4時，會發生資料落失，在兩個磁區間 copy 約800mb 的大檔有時最後的 1% 怎麼也過不去，有時是資料完全寫不進去，在解tar時或是loading很大時整個系統會凍住，都有遇過。不過現在的我是完全沒遇過了，除了穩定性有一定的提升，我的使用環境不夠嚴苛，還有就是我的運氣不錯吧。 :p

　　缺點還是有的，格式化後的空間相對上較少，bbs上有人指出 reiser3.6/reiser4 如果長時間沒有重組效能會急速惡化。(bbs上的說法，我持保留態度)

2.RIP CD他是模擬gentooo的哪個版本阿.有人用過RR4的LIVE CD嗎?兩者之間能否說明一下差異性如何..一個救援用所以注重相容性.一個注重攜帶式桌面系統嗎?

唔.... 沒用過rip，請用過的人發表意見吧。RR4的出現很簡單，官方不支援reiser4以及一些有趣的功能，有人乾脆自己作一個光碟出來，越作越大，東西愈來愈多也越有趣，就成了現在的RR4。

抱怨:這個企鵝系統好麻煩阿.分的一堆分支.新手都被教學手冊淹沒了.讓我很難脫離4色旗子系統.又要忍受他天天催我買正版...嗚嗚...哭泣中...

也可以用用Ubuntu呀，風行的套件中文資源才夠多，很多問題在 gentoo 官方論壇已經有解，這邊的討論就會比較少。選適合的東西用就好了，反正用的還不都是一樣的核心一樣的軟體，一樣叫作 linux。