Date: Mon, 9 Apr 2012 11:52:22 +0530 From: "Desai, Kashyap" <Kashyap.Desai@lsi.com> To: =?iso-8859-2?Q?Edward_Tomasz_Napiera=B3a?= <trasz@FreeBSD.org>, "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>, "McConnell, Stephen" <Stephen.McConnell@lsi.com> Subject: RE: Kernel crash at "softdep_deallocate_dependencies" Message-ID: <B2FD678A64EAAD45B089B123FDFC3ED72B96EF9167@inbmail01.lsi.com> In-Reply-To: <20120406194047.GA1673@strashydlo.local> References: <20120406130006.GC1336@garage.freebsd.pl> <201204061721.q36HLTj6030692@chez.mckusick.com> <20120406194047.GA1673@strashydlo.local>
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Thanks for such wonderful technical discussion. Things are now clear and w= e are planning to do some experiment based on your feedback. ~ Kashyap > -----Original Message----- > From: Edward Tomasz Napiera=B3a [mailto:etnapierala@googlemail.com] On > Behalf Of Edward Tomasz Napierala > Sent: Saturday, April 07, 2012 1:11 AM > To: Kirk McKusick > Cc: Desai, Kashyap; freebsd-fs@freebsd.org; Kenneth D.Merry; Pawel Jakub > Dawidek; McConnell, Stephen > Subject: Re: Kernel crash at "softdep_deallocate_dependencies" >=20 > 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. >=20 > 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. >=20 > > 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). >=20 > 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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