Date: Mon, 11 Jul 2016 15:45:11 -0600 From: Ian Lepore <ian@freebsd.org> To: Karl Denninger <karl@denninger.net>, freebsd-stable@freebsd.org Subject: Re: Not-so stable if you take a CAM error.... Message-ID: <1468273511.72182.131.camel@freebsd.org> In-Reply-To: <21f3f685-4618-e258-0538-75602608cf9b@denninger.net> References: <2b0c454b-c1a0-4b5b-e778-bf0939e90ae1@denninger.net> <op.ykfe1fvbkndu52@ronaldradial.radialsg.local> <6e9c07e1-12a6-a7cd-f775-6b0fe5a706bc@denninger.net> <1468243977.72182.118.camel@freebsd.org> <877f5e8e-c1e7-6fb0-6ceb-031ce3e68582@denninger.net> <CAKFCL4WrRS1ic1CZqcmbCEnsrD2pkh4VHPBFyB%2B-3NaNJZ%2BJkw@mail.gmail.com> <1468254746.72182.121.camel@freebsd.org> <f22ab40d-42f0-78a3-d3a7-945387259109@denninger.net> <1468258789.72182.122.camel@freebsd.org> <21f3f685-4618-e258-0538-75602608cf9b@denninger.net>
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On Mon, 2016-07-11 at 12:44 -0500, Karl Denninger wrote: > On 7/11/2016 12:39, Ian Lepore wrote: > > On Mon, 2016-07-11 at 12:30 -0500, Karl Denninger wrote: > > > On 7/11/2016 11:32, Ian Lepore wrote: > > > > On Mon, 2016-07-11 at 09:50 -0400, Brandon Allbery wrote: > > > > > On Mon, Jul 11, 2016 at 9:46 AM, Karl Denninger < > > > > > karl@denninger.net> > > > > > wrote: > > > > > > > > > > > Here's the backtrace ... sounds like expected behavior, > > > > > > which > > > > > > is > > > > > > not-so > > > > > > good all-in for a situation like this. I guess the > > > > > > strategy is > > > > > > to > > > > > > turn > > > > > > off softupdates before attempting such an update so as not > > > > > > to > > > > > > crash > > > > > > the > > > > > > host machine if there's a problem with the card. > > > > > > > > > > > I would tend to assume that removable media should not have > > > > > softupdates > > > > > enabled. Even with properly working media, it's practically > > > > > begging > > > > > for > > > > > corruption. > > > > > > > > > Writing to an sdcard without softupdates enabled will be an > > > > exercise in > > > > patience. Like, come back next week and maybe it'll be done. > > > > > > > > The only thing that comes to mind with this is maybe some sort > > > > of > > > > mount > > > > flag to say you're willing to live with any amount of > > > > filesystem > > > > corruption in lieu of panicking. I'm not sure how > > > > easy/practical > > > > that > > > > would be to implement, though. > > > > > > > > -- Ian > > > Why not force-detach the volume that takes the error instead of a > > > panic()? > > > > > Patches welcome. > > > > -- Ian > Any hints on where the routine(s) live that would forcibly detach a > volume? (I'll go digging as well but shortening the time would help > :)) > Your question assumes the existance of code that I don't know actually exists. Plug in any removable drive (like a usb thumb drive) and mount a ufs filesystem with softupdates enabled, then remove the drive while writing to it. Panic. I've always assumed that if this was easily fixable it would have been fixed long ago, and if it was fixable at all it would have been fixed by now. (Although increasingly it seems that ufs has transitioned to second-class citizenship, and lately I've even seen people mocked for using it instead of zfs). -- Ian
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