Date: Mon, 12 Jul 2010 10:08:33 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: sbruno@freebsd.org, Boris Kochergin <spawk@acm.poly.edu>, Hans Petter Selasky <hselasky@c2i.net> Subject: Re: QEMU/KVM Panic on USB Mount Message-ID: <201007121008.33603.jhb@freebsd.org> In-Reply-To: <4C37DAA2.6080102@acm.poly.edu> References: <1278695579.2436.27.camel@localhost.localdomain> <201007100016.29946.hselasky@c2i.net> <4C37DAA2.6080102@acm.poly.edu>
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On Friday, July 09, 2010 10:27:46 pm Boris Kochergin wrote: > Hans Petter Selasky wrote: > > On Friday 09 July 2010 19:12:59 Sean Bruno wrote: > > > >> In order to come up with the most convoluted problem possible, I present > >> to you screen shots of a panic from a FreeBSD VM running in QEMU > >> emulation under RedHat's KVM infrastructure. > >> > >> I presented a perfectly functional USB partition from my host machine to > >> the VM. Then I attempted to mount the partition from FreeBSD and it > >> generated the panics located here: > >> > >> http://people.freebsd.org/~sbruno/usb_panic1.png > >> http://people.freebsd.org/~sbruno/usb_panic2.png > >> > >> This is 100% reproducible. But not an emergency or anything. > >> > > > > It might be that there is a conflict that both the VM and the OS is accessing > > / loading drivers on the same USB device. The panic seems not directly related > > to USB. > > > > --HPS > > > > > I followed the code for a while and the cause of the panic appears to be > that ffs_vgetf() in /usr/src/sys/ufs/ffs/ffs_vfsops.c fails in one of > the several ways possible, causing in VFS_ROOT() in > /usr/src/sys/kern/vfs_mount.c to return a non-zero value and resulting > in the panic. I think the problem calls for someone with serious VFS chops. > > The I/O errors from the USB device are suspicious (in that they may > cause the mount code to misbehave if they occur during its course). Much of the filesystem code doesn't really handle I/O errors very gracefully. I do think trasz@ did some work a year or so ago to improve this somewhat. -- John Baldwin
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