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Date: Wed, 14 Oct 2009 15:10:26 +0200
From: Gary Jennejohn <gary.jennejohn@freenet.de>
To: Alexander Best <alexbestms@math.uni-muenster.de>
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Cc: freebsd-current@FreeBSD.org
Subject: Re: buffers not syncing correctly during shutdown
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On Wed, 14 Oct 2009 12:49:54 +0200 (CEST)
Alexander Best <alexbestms@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@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