system and desktop VFS merged

[Sean Middleditch]

Diego Calleja wrote:

>El Tue, 29 Mar 2005 23:03:19 -0800 (PST),
>Rahul Sundaram <rahulsundaram at yahoo.co.in> escribió:
>
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>>Freedesktops are not Linux specific while FUSE is.
>>    
>>
>
>I already told that. OSs who don't implement themselves userspace filesytems
>will have to live without them.
>
>What else could you want to do? Filesystem namespace is something that belongs to the
>operative system level, and it's the operative system who has the power to fix that. Trying
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>
Says who?  I say that's absolutely wrong.  The only thing that belongs 
in the kernel is stuff that requires the kernel.  You need the kernel to 
do block access.  You need the kernel to directly push bits around on 
the block device securely.

You don't need the kernel to access CIFS.  You don't need the kernel to 
access WebDAV.  You need the kernel to do the networking, but that's 
it.  There are many WebDAV implementations that work 100% absolutely 
perfectly in userspace.  They don't need the kernel.

Neither does D-VFS.  It doesn't *need* the kernel for anything.  Shoving 
craploads of code into the kernel - the absolute last place you want to 
add more code - is at its very core a bad idea.  If you can possibly 
implement something in userspace, then that's where it should be done.

Putting parts of D-VFS into the kernel buys you very, very little.  It 
can help provide compatibility to old applications.  It's hard to 
provide that compatibility without the kernel.  Possible, sure, but it 
can't be done perfectly.  And the kernel has stark disadvantages that 
I've gone over many times and *not one* of the pro-in-kernel people have 
actually addressed those issues, other than saying, "I don't care."  
That's not good enough.

The kernel cannot easily be extended with new APIs when new technologies 
become available.  It does not at all make it easy to securely and 
efficiently have bi-directional communication with userspace in response 
to in-kernel events like D-VFS would absolutely require for correct user 
interaction.

Compatibility is not a problem.  KDE and GNOME have existed for years 
with their own VFS systems.  FUSE even allows you to wrap those so that 
legacy apps get have near-perfect compatibility with those *100% 
userspace VFS implementations*.

D-VFS is not and will not be kernel based.  If you can't accept that, 
you are free to create an in-kernel extensible dynamic user-oriented VFS 
system that rocks my socks off and proves me wrong.  Let me know when 
it's done, since you guys seem to have it all figured out.


>to hide that fact by creating a standard that makes userspace filesystems anything but
>transparent is not going to change that....
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