panic after removing usb flash disk

Jeremy Chadwick koitsu at
Thu Aug 16 10:08:18 PDT 2007

On Thu, Aug 16, 2007 at 09:31:32AM -0700, Kevin Oberman wrote:
> To further complicate things, many of the major contributors to FreeBSD
> are only interested in it for its use as a server or embedded OS. This
> means that they are willing to commit resources to SMP, which they need,
> but not so willing for hot-removal of storage, which is of only slight
> value in the server and embedded OS world.

Really?  Hmm.  This got me thinking: it would benefit Juniper greatly if
they 1) stopped using single disks in their multi-thousand-dollar
routers (try dual disks with RAID 1), 2) stopped using ATA disks and
went with SCSI, and 3) put in a hot-swap backplane of some sort.

Nothing like paying US$20K for a ""enterprise"" product that uses single
ATA disks with no hotswap capability.  My point is that it WOULD benefit
some of the major contributors to rank this issue as serious.

> I am sure that a lot of people who have no professional interest in
> fixing this do have a strong personal interest and I suspect that it
> will happen before too long, but complaining about it is not really
> going to help as almost every FreeBSD desktop and mobile user has been
> bitten by this at one time or another and wants it fixed.

The problem is that as computing changes and the hardware evolves, the
underlying OS design being discussed here has not.  There have been many
real-life examples given where one cannot do anything about the
circumstances that induce the panic (USB hub losing power due to a cat
pulling the AC cord, laptops going into S1/S3 sleep mode, or server
admins who need to go to the co-lo and perform some realtime data
copying who simply forgot to umount).

I've been told that Linux handles this anomaly, but that it's also
configurable.  I believe the default configuration is that the mount
goes into read-only mode, and that if you want a panic (which many argue
is the "right thing to do"), you can request such via mount -o/fstab.

I'm glad that both sides of the "argument" agree that it's something
that needs to get fixed.  It's just an issue of when -- but the clock
is ticking, and the world isn't going to wait... :-)

| Jeremy Chadwick                                    jdc at |
| Parodius Networking                  |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |

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