From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karl Mardoff Kittilsen Subject: Re: kernel BUG at /build/buildd/linux-3.2.0/fs/btrfs/extent-tree.c:4816! Date: Tue, 29 Nov 2011 16:29:54 +0100 Message-ID: <4ED4FA72.5050804@kittilsen.org> References: <4ED437CE.3060909@kittilsen.org> <20111129151256.GJ24338@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-btrfs@vger.kernel.org To: Chris Mason Return-path: In-Reply-To: <20111129151256.GJ24338@shiny> List-ID: Den 29. nov. 2011 16:12, skrev Chris Mason: > On Tue, Nov 29, 2011 at 02:39:26AM +0100, Karl Mardoff Kittilsen wrote: >> Hi! >> >> Sending a mail on this issue, as advised on IRC. >> >> My /home file system fails to mount and the kernel seem to freeze >> and I need to do the Alt+SysRq RSNEIUB routine to boot it safely. >> The corruption happened on a 3.2-rc kernel and Ubuntu >> 11.10, but I am now running on Ubuntu 12.04 with the 3.2.0-2-generic >> kernel to see if that helped, it did not. >> btrfsck from the latest btrfs-tools returns: >> >> karl@karl-precise:~/git/btrfs-progs$ sudo ./btrfsck /dev/md0 >> ref mismatch on [2176962560 8192] extent item 480, found 1 >> Incorrect local backref count on 2176970752 root 5 owner 2101705 >> offset 368640 found 1 wanted 3925868545 >> backpointer mismatch on [2176970752 4096] > > So the crashes below were because we tried to free one of these extents. > You have two extents whose reference counts are way off. > > Unfortunately this is stored on disk, so different kernels aren't going > to fix it (yet). One of the extents is in a file with inode number > 2101705, and the other is in a btree block (2176962560). > > I'll be able to fix this soon, but we can also make a patch that changes > those BUG_ONs to just deal with the mismatch. The worst case here would > be leaking those two extents, about 12K of data. > > -chris Thank you for looking into it, and that does sounds really promising. I am available to test any patches you want tested. Is there anything else that I can do to help getting this issue fixed? Karl