kern/108199: System crash while trying to unmount manually ejected USB Flash drive

[Bruce Evans]

The following reply was made to PR kern/108199; it has been noted by GNATS.

From: Bruce Evans <bde at zeta.org.au>
To: Mark Linimon <linimon at freebsd.org>
Cc: ggg_mail at inbox.ru, freebsd-gnats-submit at freebsd.org
Subject: Re: kern/108199: System crash while trying to unmount manually
 ejected USB Flash drive
Date: Mon, 22 Jan 2007 23:56:28 +1100 (EST)

 On Mon, 22 Jan 2007, Mark Linimon wrote:
 
 > Synopsis: System crash while trying to unmount manually ejected USB Flash drive
 
 > This is a well-reported problem that is going to take some system
 > rearchitecting to fix.  The underlying layers of the file system were
 > not initially written with the criteria that file systems were dynamic.
 > But thanks for reporting.
 
 However, the underlying layers were initially more robust against panics
 although not against data loss.  They simply discarded buffers after
 the first write error.  Now, unwriteable buffers are supposed to be
 retried forever, but sometimes even that doesn't happen, since there is
 code that still hasn't caught up with the changed error handling.
 
 I think the panic was fixed in ffs a few years ago (umount -f just
 returns an error in at least my version of FreeBSD-5.2).  Some negative
 progress has been made since then, so ffs now panics near where msdosfs
 used to panic (vinvalbuf() hasn't caught up), and msdosfs doesn't get
 that far since it now panics in vop_stdfsync() in the diagnostic message
 about the problem.
 
 Bruce