Re: fcntl(2) and other file systems like XFS

From: Jim Mostek (mostek@sgi.com)
Date: Mon Mar 20 2000 - 13:44:45 EST


>
>I'm not sure why you want to fix anything: what is the problem? If you

compatability with fcntl on Unix/IRIX,
collisions can cause weirdness, not just EINVAL

>simply reject ioctls you don't understand when you get called in the fs-
>specific ioctl method, what goes wron with the existing mechanisms?

If two ioctls have the same value, but different functionality for different
file systems/drivers, the app could get unexpected results.

This isn't such a big deal. We have bigger fish to fry. ;-)
We will go ahead and use the ioctls instead of fcntls.

The issues with the ioctl vs fcntls:

        1. programs that run using fcntl() on IRIX or other unixes needs
to change to use ioctls when ported to Linux. We can build a compatability
library that intercepts fcntl and switches to ioctl or fcntl.

        2. there is no central repository for all the ioctls so there may
be collisions between ioctls and fcntls. This can be minimized as by using
/usr/include/bits/ioctls.h, /usr/include/asm/ioctl.h, and
/usr/include/asm/ioctls.h. Ideally, all ioctls would be in one place to
avoid collisions.

Thanks,

Jim

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