From mboxrd@z Thu Jan 1 00:00:00 1970 From: Erik Logtenberg Subject: Re: Kernel error during btrfs balance Date: Tue, 18 Jan 2011 15:29:04 +0100 Message-ID: <4D35A3B0.3000401@logtenberg.eu> References: <4D344EBB.6030903@logtenberg.eu> <4D35942B.2020601@logtenberg.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-btrfs@vger.kernel.org To: "Yan, Zheng " Return-path: In-Reply-To: List-ID: On 01/18/2011 03:13 PM, Yan, Zheng wrote: > On Tue, Jan 18, 2011 at 9:22 PM, Erik Logtenberg wrote: >> On 01/18/2011 01:54 AM, Yan, Zheng wrote: >>> On Mon, Jan 17, 2011 at 10:14 PM, Erik Logtenberg wrote: >>>> Hi, >>>> >>>> btrfs balance results in: >>>> >>>> http://pastebin.com/v5j0809M >>>> >>>> My system: fully up-to-date Fedora 14 with rawhide kernel to make btrfs >>>> balance do useful stuff to my free space: >>>> >>>> kernel-2.6.37-2.fc15.x86_64 >>>> btrfs-progs-0.19-12.fc14.x86_64 >>>> >>>> Filesystem had 0 bytes free, should be 45G, so on darklings advice I ran >>>> btrfs balance on the fs, while doing heavy I/O (re-running 5 backup jobs >>>> that had failed due to ENOSP). >>>> Up until the crash, btrfs balance did retrieve a couple of Gigs free >>>> space though, so that part of the plan worked just fine. >>>> >>> >>> Please try 2.6.36 kernel. >> >> Thanks for your (short) advice. Could you please elaborate. I was in >> fact using a 2.6.35.10-74.fc14.x86_64 kernel before, but darkling >> adviced me to switch to a newer kernel to reclaim free space by >> balancing -- the idea was that newer kernels have better balancing >> implementation, more effective at reclaiming free space. >> >> Now your advice is to take a small step back again, from 2.6.37 to >> 2.6.36 (which is still higher than the 2.6.35 I was using before). Is >> that because you think that 2.6.37 may have introduced the bug that I >> ran into? Do you think that 2.6.36 is still recent enough to have the >> effective balancing so that I will in fact be able to reclaim some free >> space? Or is is just a shot in the dark with no reasoning whatsoever ;) >> >> Please don't feel offended, but from your 4-word sentence I really can't >> tell. >> > > Just try narrowing down the bug, because I never saw bug like this before. Okay I can try that. Please note though that I cannot reliably reproduce the bug. At this moment I am in the middle of my second try at balancing the FS (still on 2.6.37), this time without 8 rsync's banging on the FS. So far, everything is completely stable. I could downgrade to 2.6.36 after this balance and then re-try balancing, but if this second go doesn't crash like the first try, then a succesful rebalance on 2.6.36 won't tell us much. Please note that it could be a combination of bugs. I ran into an out-of-space issue in the middle of a backup first (at that time on 2.6.35), and also noticed some minor file corruption as a result. Then I switched over to 2.6.37 to fix the out-of-space issue (as there should have been 45G free) using a balance. During that balance operation I then ran in to the bug that I reported in my previous email. So it could be the 2.6.37 kernel hitting a minor FS corruption caused by out-of-space issues with the 2.6.35 kernel. I have no idea how I could reproduce this at all. Thanks, Erik.