linux-kernel - Re: [RFC PATCH] add filesystem subtype support

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Date:	Mon, 12 Feb 2007 13:39:39 +0100 (MET)
From:	Szakacsits Szabolcs <szaka@...net.hu>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] add filesystem subtype support


Hi,

On Mon, 12 Feb 2007, Miklos Szeredi wrote:

> There's a slight problem with filesystem type representation in fuse
> based filesystems.
> 
> >From the kernel's view, there are just two filesystem types: fuse and
> fuseblk.  From the user's view there are lots of different filesystem
> types.  The user is not even much concerned if the filesystem is fuse
> based or not.  

Yes. Those who are concerned with the fstype and mount like

    mount -t fstype device mountpoint

apparently expect mount/fstab line like

    device mountpoint fstype ...

Of course the fstype could be fuse.subtype or fuseblk.subtype but that 
would add a needless complexity (also, for example ntfs-3g uses both and 
it decides run-time which one to use).

> So there's a conflict of interest in how this should be
> represented in fstab, mtab and /proc/mounts.
> 
> The current scheme is to encode the real filesystem type in the mount
> source.  So an sshfs mount looks like this:
> 
>   sshfs#user@...ver:/   /mnt/server    fuse   rw,nosuid,nodev,...
> 
> This url-ish syntax works OK for sshfs and similar filesystems.
> However for block device based filesystems (ntfs-3g, zfs) it doesn't
> work, since the kernel expects the mount source to be a real device
> name.
> 
> A possibly better scheme would be to encode the real type in the type
> field as "type.subtype".  So fuse mounts would look like this:
> 
>   /dev/hda1       /mnt/windows   fuseblk.ntfs-3g   rw,...
>   user@...ver:/   /mnt/server    fuse.sshfs        rw,nosuid,nodev,...

I think it's definitely an improvement because it solves real problems, 
though perhaps not the way users would expect.

	Szaka

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