Re: buffers not syncing correctly during shutdown

Gary Jennejohn schrieb am 2009-10-14:
> On Wed, 14 Oct 2009 12:49:54 +0200 (CEST)
> Alexander Best <alexbestms_at_math.uni-muenster.de> wrote:

> > hi there,

> > to keep it short:

> > 1. mount a removable device (e.g. an usb stick) (better use -r to
> >    prevent data
> > loss)
> > 2. unplug the device (without unmounting it)
> > 3. `shutdown -r now`

> > what happens is that the usual shutdown routine gets processed
> > until all
> > buffers are synced, but then the system stalls.

> > after resetting the system all devices (which were supposed to be
> > synced) are
> > marked dirty and are being fsck'ed.

> > cheers.
> > alex

> > oh...and i'm running FreeBSD otaku 9.0-CURRENT FreeBSD 9.0-CURRENT
> > #0 r197914:
> > Sat Oct 10 02:58:19 CEST 2009
> > root_at_otaku:/usr/obj/usr/src/sys/ARUNDEL
> > i386


> I'm inclined to say that umount'ing the file systems is failing
> because
> you pulled the USB stick out without doing umount.  Of course, that
> results in all file systems still being marked dirty.  Obviously,
> this
> pathological case isn't being handled.

> I personally don't see why it ever should be handled.  This is UNIX
> not
> Windows and users should be smart enough to know that they umount
> such
> devices before removing them otherwise nasty things can happen.

> ---
> Gary Jennejohn

this is 2009 and not the 70s/80s. the amount or non-removable devices is
declining day by day. eventually all storage devices will become removable and
freebsd should keep up with this development.

i don't think labelling this obvious bug as a grand unix feature is valid.

also there are other scenarios where this problem can occur. if the device
produces i/o errors you won't be able to unmount it even with the -f switch.

alex