VFS design question

VFS design question

[Tobias Pflug]

Hi,

A note in front: I realize that my question is rather broad and a bit
vague, sorry for that :)

The VFS is a great solution to transparently operate on different file
systems by designating an interface for file systems that separates 
file system specific code from higher levels. 

Doesn't however this very feature also represent a limiting factor in
some way? Surely you can map pretty much anything to the Common File
System model, but is or has the VFS interface design been limiting
in any way in contemporary file system design ? 

thanks for your time.
regards,
Tobi

PS: please CC I am not subscribed.thanks

Re: VFS design question

[H. Peter Anvin]

Tobias Pflug wrote:
> Hi,
> 
> A note in front: I realize that my question is rather broad and a bit
> vague, sorry for that :)
> 
> The VFS is a great solution to transparently operate on different file
> systems by designating an interface for file systems that separates 
> file system specific code from higher levels. 
> 
> Doesn't however this very feature also represent a limiting factor in
> some way? Surely you can map pretty much anything to the Common File
> System model, but is or has the VFS interface design been limiting
> in any way in contemporary file system design ? 
> 

Why does this sound like "do my homework for me"?

	-hpa

Re: VFS design question

[Tobias Pflug]

On Sat, 2007-05-19 at 11:06 -0700, H. Peter Anvin wrote:
> Tobias Pflug wrote:
> > Hi,
> > 
> > A note in front: I realize that my question is rather broad and a bit
> > vague, sorry for that :)
> > 
> > The VFS is a great solution to transparently operate on different file
> > systems by designating an interface for file systems that separates 
> > file system specific code from higher levels. 
> > 
> > Doesn't however this very feature also represent a limiting factor in
> > some way? Surely you can map pretty much anything to the Common File
> > System model, but is or has the VFS interface design been limiting
> > in any way in contemporary file system design ? 
> > 
> 
> Why does this sound like "do my homework for me"?
> 
> 	-hpa

I tried to make it clear that I am clearly lacking expertise in this
topic. I am currently working on a somewhat related topic and was hoping
to get some reactions that would point me in the right directions as it
is somewhat hard to judge the VFS design when you do not have prior
experience in writing a file system on your own. Nowhere did I ask for a
10 paged review on the matter.

Enough blablabla

Any input would be welcome. Thanks.

-Tobi

Re: VFS design question

[Bernd Eckenfels]

In article <1179611516.6558.357.camel@toontown> you wrote:
> I tried to make it clear that I am clearly lacking expertise in this
> topic. I am currently working on a somewhat related topic and was hoping
> to get some reactions that would point me in the right directions as it
> is somewhat hard to judge the VFS design when you do not have prior
> experience in writing a file system on your own. Nowhere did I ask for a
> 10 paged review on the matter.

VFS abstraction is not too limiting, because the interface to user space is
fixed by posix or other standards in the libc. So als long as the new
filesystem want to support that semantic, it is not really limited.

There are some cases which are a bit hard, for example inode numbers -
especially when you want to provice NFS support, but that is not
specifically a VFS Problem.

And: VFS has evolved over time, that is the advantage of open source, you
can just include new functions in the old filesystems when you think you
need to impriove the framework.

That said, if you look at Reiser4 for example, there are some plug-in
extensions which are not yet possible in VFS, since it is a more high level
interface...

There are some different file close/lock semantics out there, and VFS does
not even try to abstract them.

gruss
Bernd