Re: dmfs for 2.5.51

[Greg KH <greg@kroah.com>]

On Thu, Dec 12, 2002 at 05:50:01PM -0800, Andrew Morton wrote:
> Greg KH wrote:
> > 
> > ..
> > +Examples
> > +--------
> > +
> > +Example commands will make things a bit clearer:
> 
> hm.  The whole thing seems hokey to me.  Not sure why.

I agree.  It doesn't feel right.  I mean, doing a mkdir(1) to create a
device, which causes files to be created automagically in that
directory?  Something needs to change here, and I proposed a single file
to write to that creates the device, but was shot down by the author.

Anyone else have any ideas?

> > ...
> > +  echo -e "0 56 linear /dev/hda3 0\n56 102344 linear /dev/hda4 0" > table
> 
> Maybe this is why.

Heh, yeah, welcome to parsers in the kernel :)
But the dm code today does much the same thing with ioctls, passing a
string down to the loaded modules below it.  So there is a bit of
president.  Even if it is ugly :)

> > ...
> > +static struct page *find_page(struct dmfs_file *f, loff_t len, int fill)
> 
> This is called under spinlock.
> 
> > ...
> > +                       void *addr = (void *) __get_free_page(GFP_KERNEL);
> 
> whoops.

Nice catch.  I'm not sure that the find_page(), __io() and friends
functions are really needed at all.

Thanks for looking at this.  I hope the dm authors can help explain
more.

greg k-h