Date: Thu, 7 May 2015 21:17:42 +0200 From: Bernd Walter <ticso@cicely7.cicely.de> To: Dmitry Sivachenko <demon@freebsd.org> Cc: Edward Tomasz Napiera??a <trasz@freebsd.org>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Ryan Stone <rysto32@gmail.com> Subject: Re: What's required to make removal of a mounted USB stick safe? Message-ID: <20150507191742.GE44366@cicely7.cicely.de> In-Reply-To: <D4835143-A763-4C04-BAEC-65580E847C11@FreeBSD.org> References: <CAFMmRNwTi2GOEHN1tDQ7o1-VAtykT%2Bz3g%2B70qaDMenThSrSRgQ@mail.gmail.com> <1306708F-0872-4D02-9C88-70F683018C39@FreeBSD.org> <D4835143-A763-4C04-BAEC-65580E847C11@FreeBSD.org>
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On Thu, May 07, 2015 at 01:12:28PM +0300, Dmitry Sivachenko wrote: > > > On 7 ?????? 2015 ??., at 9:23, Edward Tomasz Napiera??a <trasz@FreeBSD.org> wrote: > > > > > > Dnia 6 maj 2015 o godz. 22:49 Ryan Stone <rysto32@gmail.com> napisa??(a): > > > >> Currently FreeBSD stands a fair chance at panicking if a mounted USB drive > >> is removed while I/O is in flight. Does anybody know what work is involved > >> to have the kernel safely recover from this case? Losing data from the > >> drive is expected of course but there's no reason that the entire kernel > >> has to crash. > > > > I've spent some time on this few years ago, and got it to work, except for one case: UFS with softupdates. It's possible that some regressions have been introduced since then. What's the filesystem? Do you have a backtrace? > > > Recently I forgot to unmount a partition on failed disk (UFS+SU), and after disk was removed it was a kernel panic (something related to SU but I did not save the trace). Another related problem point with removeable media is the filesystem state. It can happen that the filesystem on a mounted media is broken and panic the kernel. The only way to work around is fsck'ing the filesystem before mounting, which can introduce an unacceptable delay. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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