> -----Original Message----- > From: Marc MERLIN [mailto:marc@xxxxxxxxxxx] > Sent: Wednesday, April 23, 2014 11:58 PM > To: Пламен Петров > Cc: linux-btrfs@xxxxxxxxxxxxxxx > Subject: Re: Can anyone boot a system using btrfs root with linux 3.14 or > newer? > > On Wed, Apr 23, 2014 at 10:37:44PM +0300, Пламен Петров wrote: > > > So now, we're kind of guessing. To save us all time, could you > > > capture a serial console boot from the running 3.13 and then the failing > 3.14. > > > > Well, for the details - see for example here: > > https://bugzilla.kernel.org/attachment.cgi?id=133111 > > how does a 3.14.1 built the way described earlier fails. > > Thanks, that helps. > Except, now I'm perplexed. > > It indeed shows btrfs loaded and your block device being detected. > However it does not show a btrfs mount error. > > I haven't had to debug this in a while, but I'm wondering if you're having a > block device problem. > > It may help to look up what error -38 translates into for that mount error. My searches so far failed to return anything useful to solving this problem. > > > And for that matter - see the whole bugzilla bug entry - I went on and > bisected this, using the linux-stable git tree, and after that landed me on the > commit that introduces some "shiny new btrfs feature" for 3.14 - I decided > my git bisection has gone wrong. And because I reported it on April 17-th and > since then there has been no activity on the bugzilla entry besides me > updating it - I posted my problem here, for more eyes to see. > > One easier way to debug this would be to create an initrd for 3.13 and 3.14. > Make sure it works with 3.13 first, then boot 3.14 and see what error you get. > You'll get an error from mount(8) and not the kernel and you'll be dropped to > a shell, giving you more debug options. > The initrd way will require some reading up on my part - so will have to wait for tomorrow. > > > My guess is that if you diff both you'll likely find what went > > > wrong, but if not you can post here. > > > > See the result of "diff config-v3.14.1-mix64 config-v3.13.11-mix64" in the > attached file. > > diff -u is your friend ;) > but diff looks reasonable. > > > > As for the btrfs FS format, it has not changed in a way that new > > > kernels wouldn't be able to mount an FS from a year ago or more. > > > > Good to know! Thanks! > > Of course, that doesn't mean you didn't find a bug saying otherwise. > > If you try from an initrd, it'll make it easier to debug. I will have to lookup how to do that... > You don't have to build a > new kernel or make btrfs a module, just mounting a working initrd and then > trying this again with userland tools will help debug. > (alternatively, rescue boot media with your kernel would work too, but that's > likely more work to build than an initrd) Not more work - just replaced the kernel on the setup/rescue media with mine and the result is the same - see attached image file. > Actually, you could also use your VM > setup to boot another linux image running ext4 as root with your new kernel, > setup your existing drive as sdb, and try to mount it then. > > Marc > -- Thanks for the ideas, Marc. It's nice to see someone trying to help! ----------------- Plamen Petrov
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