Re: [PATCH] Device-mapper submission 6/7

From: Jeff Garzik (
Date: Wed Oct 16 2002 - 09:20:30 EST

Joe Thornber wrote:
> On Tue, Oct 15, 2002 at 02:15:35PM -0400, Jeff Garzik wrote:
>>>[Device mapper]
>>>Provide a traditional ioctl based interface to control device-mapper
>>>from userland.
>>If you're adding a new interface, there should be no need to add new
>>ioctls and all that they entail. Just control via a ramfs-based fs...
> We originally did have a fs based interface written by Steve
> Whitehouse. However at the time (about a year ago) it wasn't obvious
> that everyone would think it a good idea. Also the code was
> significantly larger than the ioctl interface. I would be more than
> happy to do away with the ioctl stuff if people are now in full
> agreement that an fs interface is the way to go.

Which people didn't like it? ;-)

AFAIK Linus and Al Viro (and myself <g>) have always considered ioctls
an ugly -ism that should have never made it into Unix. Over and above
the Unix/VFS design problems with ioctl(2), ioctl(2) is a pain for
people like David Miller who must maintain 32<->64 bit ioctl translation
layers for their architecture. ia64 and x64-64 must do this too. Each
ioctl you add is an additional headache for them.

We now have libfs.c in 2.5.x that makes ramfs-based filesystems even
more tiny, too. With the added flexibility of an fs -- it makes the
userland tools much more simple and sane -- and the pain of ioctls, it
seems a clear choice for new interfaces.


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