[Crash-utility] dev command deteriorates with new kernels

[Dave Anderson]

----- "Bob Montgomery" <bob.montgomery at hp.com> wrote:

> On Mon, 2009-06-08 at 19:50 +0000, Dave Anderson wrote:
> 
> Regarding blkext 259
> > 
> > Correction -- it does appear in the major_names[] array, in a
> 2.6.30
> > kernel for example, like this:
> > 
> >   crash> p * major_names[4]
> >   $51 = {
> >     next = 0x0, 
> >     major = 259, 
> >     name = "blkext\000\000\000\000\000\000\000\000\000"
> >   }
> > 
> > where it appears to be the only major_names[] entry whose "major"
> value
> > doesn't equal the index into the array (i.e., 259 != 4).  But the
> > bdev_map.probes[4] entry is unused.
> 
> The blkext is supposed to get used as soon as someone wants to put more
> than 15 partitions on an sd disk.  (Explanation at
> http://thread.gmane.org/gmane.linux.kernel/701825)
> 
> Then the upper partitions will appear as minors of 259.  When that
> starts happening more, having a way to see it might (*might*) be
> interesting.
> 
> > > At this point I'm about ready to deprecate the whole command... 
> ;-)
> 
> And at this point I couldn't really argue much :-)  I obviously hadn't
> used the command for a while.  I was casting around, hoping it would
> maybe help me find the diskstats stuff for the block devices.  I was
> trying to answer a question like "How much disk activity was going on
> before this crashed?"
> 
> When I tried the dev command and it bombed at the chrdev stuff before
> getting to the blkdev stuff, I was motivated to get it going enough to
> see if it would help answer my question, but it doesn't print anything
> (like hd_struct pointers) that could help me with my problem.  But I
> figured someone had once wanted that device info, so it might as well
> work...
 
OK, I understand...

But anyway, given the command's current capability, do you think that the 
alternative -f option should just be thrown out, and that all devices
should be dumped regardless whether they have file_operations associated
with them or not?

Dave