On Sun, Sep 04, 2005 at 01:35:54PM -0700, Ben Rockwood wrote:
> Christoph Hellwig wrote:
>
> >You don't seem to have any expertise about linux filesystems, and what
> >you're writing is both totally offtopic here and completely wrong.
> >
> >Please let this sub-thread die.
> >
> >
> Since you are the expert why don't you give us some details on where
> we're wrong? [1] My observations are from the standpoint of a long time
> user, I never got involved in ReiserFS directly, so there is plenty that
> I don't know.
I think you're pretty right on the track. It's Felix who's spreading
rather doubios half-informed stuff around.
> The thread got off topic, the only real point I cared to make was that
> if ReiserFS was made avalible for OpenSolaris it would be pretty kool,
> reguardless of any opinions on the project of the filesystem itself.
> The more the merrier.
Of course. There's a reiserfs port for freebsd which might be used as
a start by anyone who cares enough.
Ext2/ext3 are probably more interesting, as they have a wider userbase
and support for them is much simpler. I wouldn't recommend using the
existing Solaris ext2 driver, as it's has various problems: it's read-only,
based on a very old ext2 codebase that lacks features used by default
on modern Linux installation and has many known bugs, the Solaris glue
isn't exactly nicely written, and it's licensed under the GPL [1].
But given that ext2/ext3 is so similar to UFS allows for a much nicer
implementation anyway, either by allowing different filesystem format
personality for a common UFS layer as NetBSD did it in their BSD licensed
ext2 implementation or as by takin the UFS codebase and chaning it to
support the ext2 ondisk format, I did something like that for a never
released [2] ext2 driver for UnixWare7. I took the UnixWare sfs [3]
code and modified it to support the ext2 ondisk format. This would
cover access to ext3 support aswell as ext2 and ext3 are the same basic
ondisk format [4], the ext3 driver just supports a few additional
features over the ext2 driver, thus you can access a cleanly unmounted
ext3 filesystem as if it were ext2. Note that the ext2/ext3 userspace
code (e2fsprogs) is ported to Solaris already.
[1] The GPL's intention is to not allow linking into programs with
incompatible licenses. Whether this is actually enforceable in
court for the case of kernel modules is a different question,
but the module at least has licensing problems because of that.
[2] And there's no chance it could be release, sorry
[3] In UnixWare 2 the ufs code grew support for security attributes and was
renamed to sfs. The ufs driver is a tiny wrapper that calls into common
code with just a single different flag from sfs
[4] ext2/ext3 has three feature bitmaps in the superblock, the compat,
ro_compat and incompat flags. The compat features are supported by
newer kernels for r/w transparently, only fsck and other userspace
utilities need to be updates, ro_compat are supported read-only by
older filesystems and incompat flags not at all. An ext3 filesystem
is indicated by having EXT2_FEATURE_COMPAT_HAS_JOURNAL set, and on
an unclean unmount that needs log recovery EXT3_FEATURE_INCOMPAT_RECOVER
is set aswell. There's also some new flags only supported by the ext3
driver but not the ext2 driver in Linux.
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