Re: bug in blkdev <-> VFS interaction. (oops) (fwd)

From: Alexander Viro (viro@math.psu.edu)
Date: Sat Sep 16 2000 - 13:50:44 EST


On Sat, 16 Sep 2000, Alain Knaff wrote:

> >Flush
>
> What is so shocking about flushing away the cache for a
> write-protected floppy?

Erm... The fact that final close() will do it anyway? Oh, and the fact
that we have a generic ioctl() doing the same.

> > and format on write-protected floppy?
>
> Agreed. However, for format, we have a different issue: if you open an
> unformatted floppy the normal way, you might get an unreasonable delay
> while the floppy driver is trying to autosense its format (which is
> not yet there...). Hence the special open("/dev/fd0", 3) format which
> gives back a filedescriptor which is neither readable, nor writable,
> but which can still be used for ioctls.

Yep. You can use odd flags or you can use different name - in that case
open() has only 2 arguments, so that's about all choice we have. The thing
being, yet another file is normal - nothing strange about it (everything
is... and all such). Unusual flags, though...

> > *PRM and FDTWADDLE - why
> >not? That leaves FDRAWCMD, FDRESET and FDEJECT. Looks like controller
> >commands for me...
>
> What do you mean by "controller" commands? Personnally, I'd find it
> extremely bizarre to read a disk using sysctl or /proc/floppy/rawcmd

How about /dev/fd0ctl? I also find use of sysctl() an extremely bizarre
way to read the disk. The thing being, ioctl() is not better. Dunno about
you, but I prefer to use read() for reading...

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