Date: Fri, 6 Apr 2012 21:40:48 +0200 From: Edward Tomasz =?utf-8?Q?Napiera=C5=82a?= <trasz@FreeBSD.org> To: Kirk McKusick <mckusick@mckusick.com> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>, Pawel Jakub Dawidek <pjd@freebsd.org>, "Kenneth D.Merry" <ken@freebsd.org>, "Desai, Kashyap" <Kashyap.Desai@lsi.com>, "McConnell, Stephen" <Stephen.McConnell@lsi.com> Subject: Re: Kernel crash at "softdep_deallocate_dependencies" Message-ID: <20120406194047.GA1673@strashydlo.local> In-Reply-To: <201204061721.q36HLTj6030692@chez.mckusick.com> References: <20120406130006.GC1336@garage.freebsd.pl> <201204061721.q36HLTj6030692@chez.mckusick.com>
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On Fri, Apr 06, 2012 at 10:21:29AM -0700, Kirk McKusick wrote: > Following through on Pawel Jakub Dawidek's comments, there is no > way that the filesystem can recover when a large piece of its has > disappeared. The panic that you are getting is because the soft > updates system realizes that allowing writes to continue on the > filesystem will cause it to be corrupted in an unrepairable way. > As it has no way to cleanly downgrade it to read-only or unmount > it, its only choice is to panic. Actually, there is a third way, which is what UFS mounted without softupdates does: do nothing. This works, because when ENXIO gets returned, the device is already gone. > If you do not like this panic, you can disable soft updates using: > > tunefs -n disable <filesystem> > > Absent the soft updates integrity checking, the filesystem will > carry on a good bit longer (though after a reboot it will likely > be unrecoverable even if you have put the disk back into it). Apart of a situation where ENXIO would be returned, but the device would stay accessible, which doesn't happen, afaik, what will actually happen is that all the operations on a filesystem will return ENXIO, except for reads for which the data is still in cache. Nothing will get written, so no further damage will be done, and it will be possible to forcibly unmount the filesystem without panicing.
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