Kernel BUG shortly after mounting btrfs filesystem

[Chris Halse Rogers]

This bug happens entirely reproducibly after mounting a multi-disc btrfs filesystem I have. It is reproducible on the current Vivid 3.18 kernel and the mainline 3.19-rc5 build; I recall this bug also happening on Utopic's 3.16 kernel, but don't have logs.

All processes that touch the filesystem then hang indefinitely in the kernel.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-image-3.18.0-9-generic 3.18.0-9.10
ProcVersionSignature: Ubuntu 3.18.0-9.10-generic 3.18.2
Uname: Linux 3.18.0-9-generic x86_64
AlsaDevices:
 total 0
 crw-rw----+ 1 root audio 116, 1 Jan 21 10:03 seq
 crw-rw----+ 1 root audio 116, 33 Jan 21 10:03 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.15.1-0ubuntu2
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Wed Jan 21 10:05:37 2015
InstallationDate: Installed on 2015-01-20 (0 days ago)
InstallationMedia: Ubuntu-Server 15.04 "Vivid Vervet" - Alpha amd64 (20150116)
IwConfig:
 lo no wireless extensions.

 em1 no wireless extensions.
MachineType: HP ProLiant MicroServer
PciMultimedia:

ProcFB: 0 radeondrmfb
ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz-3.18.0-9-generic root=UUID=b5d97f60-81e7-4dd8-a8a7-b2bfef3eeb52 ro rootflags=subvol=@ init=/lib/systemd/systemd
RelatedPackageVersions:
 linux-restricted-modules-3.18.0-9-generic N/A
 linux-backports-modules-3.18.0-9-generic N/A
 linux-firmware 1.140
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 10/01/2013
dmi.bios.vendor: HP
dmi.bios.version: O41
dmi.chassis.type: 7
dmi.chassis.vendor: HP
dmi.modalias: dmi:bvnHP:bvrO41:bd10/01/2013:svnHP:pnProLiantMicroServer:pvr:cvnHP:ct7:cvr:
dmi.product.name: ProLiant MicroServer
dmi.sys.vendor: HP

[Chris Halse Rogers (raof)]

Relevant snippet of dmesg:

[ 70.591237] BTRFS info (device sdd): disk space caching is enabled
[ 71.428714] BTRFS: bdev /dev/sdc errs: wr 0, rd 0, flush 0, corrupt 371004212, gen 0
[ 102.225649] ------------[ cut here ]------------
[ 102.225748] kernel BUG at /build/buildd/linux-3.18.0/fs/btrfs/inode.c:3123!
[ 102.225871] invalid opcode: 0000 [#1] SMP
[ 102.225950] Modules linked in: radeon kvm_amd kvm ttm amd64_edac_mod drm_kms_helper k10temp edac_core edac_mce_amd drm i2c_algo_bit tpm_infineon sp5100_tco i2c_piix4 shpchp mac_hid autofs4 btrfs xor raid6_pq pata_acpi hid_generic tg3 usbhid hid pata_atiixp ptp pps_core ahci libahci
[ 102.226483] CPU: 1 PID: 1456 Comm: btrfs-cleaner Not tainted 3.18.0-9-generic #10-Ubuntu
[ 102.226624] Hardware name: HP ProLiant MicroServer, BIOS O41 10/01/2013
[ 102.226748] task: ffff8800d2aaa800 ti: ffff8800d2ba8000 task.ti: ffff8800d2ba8000
[ 102.226878] RIP: 0010:[<ffffffffc03dd210>] [<ffffffffc03dd210>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[ 102.227089] RSP: 0018:ffff8800d2babc38 EFLAGS: 00010286
[ 102.227183] RAX: 00000000ffffffe4 RBX: ffff88011914b800 RCX: ffff8800d193d000
[ 102.227306] RDX: 000000000000019a RSI: 0000000000040000 RDI: ffff8800d193d138
[ 102.227429] RBP: ffff8800d2babc78 R08: ffff8800d0e0f7b8 R09: ffffffffc03ad66a
[ 102.227551] R10: ffff88011fc9cbe0 R11: ffffea00046ca040 R12: ffff8800d0e19910
[ 102.227674] R13: ffff88011b0d62c0 R14: ffff88011914bc58 R15: 0000000000000001
[ 102.227798] FS: 00007fcbf6678700(0000) GS:ffff88011fc80000(0000) knlGS:0000000000000000
[ 102.227938] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 102.228038] CR2: 00007fcbf5260d68 CR3: 00000000d2fd7000 CR4: 00000000000007e0
[ 102.228160] Stack:
[ 102.228197] ffff8800d2babc78 ffffffffc041b61d ffff8800d193d000 ffff8800d0b66000
[ 102.228334] ffff88011b281120 0000000000000002 ffff8800d0e19910 ffff8800d2ae7600
[ 102.228470] ffff8800d2babd08 ffffffffc03c6d66 ffff88011b281128 ffff88011b2811a0
[ 102.228605] Call Trace:
[ 102.228695] [<ffffffffc041b61d>] ? lookup_free_space_inode+0xcd/0xf0 [btrfs]
[ 102.228847] [<ffffffffc03c6d66>] btrfs_remove_block_group+0x136/0x520 [btrfs]
[ 102.229012] [<ffffffffc040097b>] btrfs_remove_chunk+0x68b/0x800 [btrfs]
[ 102.229157] [<ffffffffc03c736e>] btrfs_delete_unused_bgs+0x21e/0x250 [btrfs]
[ 102.229308] [<ffffffffc03cee24>] cleaner_kthread+0x154/0x1b0 [btrfs]
[ 102.229449] [<ffffffffc03cecd0>] ? check_leaf+0x360/0x360 [btrfs]
[ 102.229563] [<ffffffff810949fb>] kthread+0xdb/0x100
[ 102.229655] [<ffffffff81094920>] ? kthread_create_on_node+0x1c0/0x1c0
[ 102.229773] [<ffffffff817b51bc>] ret_from_fork+0x7c/0xb0
[ 102.229870] [<ffffffff81094920>] ? kthread_create_on_node+0x1c0/0x1c0
[ 102.229983] Code: 60 04 00 00 e9 b0 fe ff ff 66 90 89 45 c8 f0 41 80 64 24 80 fd 4c 89 e7 e8 ee 23 fe ff 8b 45 c8 e9 1b ff ff ff 66 0f 1f 44 00 00 <0f> 0b b8 f4 ff ff ff e9 10 ff ff ff 4c 89 f7 45 31 f6 e8 29 7b
[ 102.230511] RIP [<ffffffffc03dd210>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[ 102.230669] RSP <ffff8800d2babc38>
[ 102.230794] ---[ end trace 7bb8d319159a4c32 ]---

[Brad Figg (brad-figg)]

This change was made by a bot.

[Chris Halse Rogers (raof)]

Relevant to my interests:
https://lkml.org/lkml/2014/10/9/733

[Colin Ian King (colin-king)]

I believe this was fixed with the following upstream commit. This now in vivid.

commit 3d84be799194147e04c0e3129ed44a948773b80a
Author: Forrest Liu <email address hidden>
Date: Wed Feb 11 14:24:12 2015 +0800

    Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group

[Colin Ian King (colin-king)]

The above patch won't backport to 3.16, also I can't reproduce the issue on 3.16, but can with 3.18 w/o the above fix.

[Chris Halse Rogers (raof)]

I think I may have mis-remembered encountering the bug in 3.16; I'm pretty sure the broken commit referenced in https://lkml.org/lkml/2014/10/9/733 was in 3.17 but not 3.16.

[Colin Ian King (colin-king)]

Chris, I believe that vivid now has the fix you require, so are you OK with closing this bug now?

[Chris Halse Rogers (raof)]

I am just in the process of rebooting that server. I'll check that the
filesystem mounts, and then close the bug.

If for some reason I forget about reporting back, that probably means
that everything's worked. :)

[Chris Halse Rogers (raof)]

Sorry, no dice:

[ 1101.894735] kernel BUG at /build/buildd/linux-3.19.0/fs/btrfs/inode.c:3142!
[ 1101.894862] invalid opcode: 0000 [#1] SMP
[ 1101.894952] Modules linked in: binfmt_misc rc_it913x_v2 it913x kvm_amd amdkfd amd_iommu_v2 kvm radeon af9033 ttm drm_kms_helper dvb_usb_af9035 dvb_usb_v2 dvb_core amd64_edac_mod drm k10temp edac_core edac_mce_amd rc_core i2c_algo_bit shpchp i2c_piix4 tpm_infineon mac_hid autofs4 btrfs xor raid6_pq pata_acpi ahci tg3 ptp pps_core libahci pata_atiixp
[ 1101.895721] CPU: 0 PID: 2536 Comm: btrfs-cleaner Not tainted 3.19.0-12-generic #12-Ubuntu
[ 1101.895866] Hardware name: HP ProLiant MicroServer, BIOS O41 10/01/2013
[ 1101.895991] task: ffff88009fa02740 ti: ffff88009c830000 task.ti: ffff88009c830000
[ 1101.896124] RIP: 0010:[<ffffffffc013f970>] [<ffffffffc013f970>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[ 1101.896339] RSP: 0018:ffff88009c833c38 EFLAGS: 00010286
[ 1101.896436] RAX: 00000000ffffffe4 RBX: ffff8800a2320800 RCX: ffff8800a80dd000
[ 1101.896563] RDX: 000000000000019c RSI: 0000000000040000 RDI: ffff8800a80dd138
[ 1101.896689] RBP: ffff88009c833c78 R08: ffff8800a4c3ef28 R09: ffffffffc010fafa
[ 1101.896814] R10: ffff88011fc1d790 R11: ffffea0002d8ff00 R12: ffff8800a4d81100
[ 1101.896940] R13: ffff8800d2051420 R14: ffff8800a2320c58 R15: 0000000000000001
[ 1101.897068] FS: 00007fc96ca70740(0000) GS:ffff88011fc00000(0000) knlGS:0000000000000000
[ 1101.897211] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 1101.897313] CR2: 00007fc5b37e7000 CR3: 00000000d1991000 CR4: 00000000000007f0
[ 1101.897439] Stack:
[ 1101.897479] ffff88009c833c78 ffffffffc017dd0d ffff8800a80dd000 ffff8800a69dd000
[ 1101.897632] ffff8800b63fc090 ffff8800a4d81100 ffff88009cf8c800 ffff8800b6264000
[ 1101.897784] ffff88009c833d08 ffffffffc01292ca ffff8800b63fc098 ffff8800b63fc110
[ 1101.897936] Call Trace:
[ 1101.898031] [<ffffffffc017dd0d>] ? lookup_free_space_inode+0xcd/0xf0 [btrfs]
[ 1101.898189] [<ffffffffc01292ca>] btrfs_remove_block_group+0x13a/0x760 [btrfs]
[ 1101.898358] [<ffffffffc0162e4a>] btrfs_remove_chunk+0x63a/0x760 [btrfs]
[ 1101.898507] [<ffffffffc0129b39>] btrfs_delete_unused_bgs+0x249/0x270 [btrfs]
[ 1101.898664] [<ffffffffc01320d4>] cleaner_kthread+0x144/0x1a0 [btrfs]
[ 1101.898808] [<ffffffffc0131f90>] ? check_leaf+0x360/0x360 [btrfs]
[ 1101.898927] [<ffffffff81094759>] kthread+0xc9/0xe0
[ 1101.899019] [<ffffffff81094690>] ? kthread_create_on_node+0x1c0/0x1c0
[ 1101.899141] [<ffffffff817c91d8>] ret_from_fork+0x58/0x90
[ 1101.899242] [<ffffffff81094690>] ? kthread_create_on_node+0x1c0/0x1c0
[ 1101.899358] Code: 60 04 00 00 e9 b0 fe ff ff 66 90 89 45 c8 f0 41 80 64 24 80 fd 4c 89 e7 e8 9e 21 fe ff 8b 45 c8 e9 1b ff ff ff 66 0f 1f 44 00 00 <0f> 0b b8 f4 ff ff ff e9 10 ff ff ff 4c 89 f7 45 31 f6 e8 e9 93
[ 1101.900087] RIP [<ffffffffc013f970>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[ 1101.900251] RSP <ffff88009c833c38>
[ 1101.918149] ---[ end trace 02688f585e76e0a8 ]---
chris@Bebop:~⟫ uname -a
Linux Bebop 3.19.0-12-generic #12-Ubuntu SMP Fri Apr 3 04:03:26 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

[Colin Ian King (colin-king)]

Can you try the latest 4.0-rc7 kernel to see if this fixes it? http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-rc7-vivid/

[Chris Halse Rogers (raof)]

Hm. The rc7 kernel doesn't seem to have that bug, but it *does* seem to have deleted all but 50MB of data on that array.

[Chris Halse Rogers (raof)]

So, let's call that a qualified success?

[Bill (bill-launchpad)]

I'm getting the same issue listed above with linux-image-3.19.0-18-generic:amd64

Initially the issue came as described in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1442884/comments/4, but after a reboot, it happens at boot.

I'm about to try updating to the newest kernel I found for vivid in http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.1-rc2-vivid/

[ 21.246397] ------------[ cut here ]------------
[ 21.246401] kernel BUG at /build/buildd/linux-3.19.0/fs/btrfs/inode.c:3142!
[ 21.246404] invalid opcode: 0000 [#1] SMP
[ 21.246426] Modules linked in: cfg80211 binfmt_misc snd_hda_codec_analog snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec hp_wmi snd_hwdep snd_pcm sparse_keymap snd_seq_midi snd_seq_midi_event snd_rawmidi kvm snd_seq snd_seq_device snd_timer edac_core k8temp edac_mce_amd serio_raw snd soundcore 8250_fintek shpchp tpm_infineon i2c_piix4 mac_hid nfsd parport_pc auth_rpcgss ppdev lp nfs_acl lockd grace parport sunrpc autofs4 btrfs xor raid6_pq hid_generic usbhid hid amdkfd amd_iommu_v2 radeon tg3 psmouse ptp ahci libahci i2c_algo_bit floppy ttm pps_core drm_kms_helper wmi drm
[ 21.246429] CPU: 1 PID: 492 Comm: btrfs-cleaner Not tainted 3.19.0-18-generic #18-Ubuntu
[ 21.246430] Hardware name: Hewlett-Packard HP Compaq dc5850 Small Form Factor/3029h, BIOS 786F6 v01.09 04/09/2008
[ 21.246432] task: ffff8800c38244b0 ti: ffff8800c8a00000 task.ti: ffff8800c8a00000
[ 21.246469] RIP: 0010:[<ffffffffc056e970>] [<ffffffffc056e970>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[ 21.246470] RSP: 0018:ffff8800c8a03c38 EFLAGS: 00010286
[ 21.246471] RAX: 00000000ffffffe4 RBX: ffff880197227000 RCX: ffff8800c3b1d000
[ 21.246472] RDX: 00000000000002f8 RSI: 0000000000040000 RDI: ffff8800c3b1d138
[ 21.246473] RBP: ffff8800c8a03c78 R08: ffff880034915fc8 R09: ffffffffc053eafa
[ 21.246473] R10: ffff88019fc9dc40 R11: ffffea0003234880 R12: ffff880034916438
[ 21.246474] R13: ffff8800c8d1f420 R14: ffff880197227458 R15: 0000000000000001
[ 21.246476] FS: 00007f2f35ebd740(0000) GS:ffff88019fc80000(0000) knlGS:0000000000000000
[ 21.246476] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 21.246477] CR2: 00007f1497f38f50 CR3: 00000000ce316000 CR4: 00000000000007e0
[ 21.246478] Stack:
[ 21.246480] ffff8800c8a03c78 ffffffffc05acc8d ffff8800c3b1d000 ffff880197225800
[ 21.246482] ffff8800c8d22f30 ffff880034916438 ffff8800c8249c00 ffff8800ca75c120
[ 21.246483] ffff8800c8a03d08 ffffffffc05582ca ffff8800c8d22f38 ffff8800c8d22fb0
[ 21.246484] Call Trace:
[ 21.246506] [<ffffffffc05acc8d>] ? lookup_free_space_inode+0xcd/0xf0 [btrfs]
[ 21.246520] [<ffffffffc05582ca>] btrfs_remove_block_group+0x13a/0x760 [btrfs]
[ 21.246537] [<ffffffffc0591e4a>] btrfs_remove_chunk+0x63a/0x760 [btrfs]
[ 21.246551] [<ffffffffc0558b39>] btrfs_delete_unused_bgs+0x249/0x270 [btrfs]
[ 21.246564] [<ffffffffc05610d4>] cleaner_kthread+0x144/0x1a0 [btrfs]
[ 21.246578] [<ffffffffc0560f90>] ? check_leaf+0x360/0x360 [btrfs]
[ 21.246584] [<ffffffff81094739>] kthread+0xc9/0xe0
[ 21.246586] [<ffffffff81094670>] ? kthread_create_on_node+0x1c0/0x1c0
[ 21.246591] [<ffffffff817c9858>] ret_from_fork+0x58/0x...

[Bill (bill-launchpad)]

FYI, the upgrade to http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.1-rc2-vivid/ appears to have fixed the issue for me.

[Raoul Bhatia (raoul-bhatia)]

This bug has effected me with linux-image-extra-3.19.0-26-generic & linux-image-3.19.0-26-generic.

I was doing an "rsync" job when it completely blocked.

Unable to kill rsync, not even with "kill -9".
Unable to "reboot -fn".
Only hard resetting the server worked.

(However, I was able to operate on ext4 partitions as I used to).

[Wed Aug 19 23:24:01 2015] ------------[ cut here ]------------
[Wed Aug 19 23:24:01 2015] kernel BUG at /build/linux-UKwbSJ/linux-3.19.0/fs/btrfs/inode.c:3142!
[Wed Aug 19 23:24:01 2015] invalid opcode: 0000 [#1] SMP
[Wed Aug 19 23:24:01 2015] Modules linked in: cpuid nf_log_ipv4 xt_nat vhost_net vhost macvtap macvlan xts gf128mul xt_CHECKSUM ipt_MASQUERADE nf_nat_masquerade_ipv4 ebtable_fil
ter ebtables iptable_nat nf_nat_ipv4 ipt_REJECT nf_reject_ipv4 iptable_mangle iptable_raw nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_tftp nf_nat_snmp_basic nf_nat_sip nf_nat_pptp n
f_nat_proto_gre nf_nat_irc nf_nat_h323 nf_nat_ftp nf_nat_amanda ipmi_devintf iptable_filter ip_tables ipmi_si ipmi_msghandler nf_log_ipv6 nf_log_common xt_recent ip6table_nat nf
_nat_ipv6 nf_nat xt_comment ip6t_REJECT nf_reject_ipv6 xt_addrtype xt_physdev br_netfilter xt_mark ip6table_mangle nf_conntrack_snmp xt_tcpudp xt_CT ip6table_raw xt_multiport nf
_conntrack_ipv6 nf_defrag_ipv6 xt_conntrack xt_NFLOG nfnetlink_log xt_LOG nf_conntrack_tftp nf_conntrack_sip nf_conntrack_sane
[Wed Aug 19 23:24:01 2015] nf_conntrack_proto_udplite nf_conntrack_proto_sctp nf_conntrack_pptp nf_conntrack_proto_gre nf_conntrack_netlink nfnetlink nf_conntrack_netbios_ns nf
_conntrack_broadcast nf_conntrack_irc nf_conntrack_h323 nf_conntrack_ftp ts_kmp nf_conntrack_amanda nf_conntrack ip6table_filter ip6_tables x_tables bridge stp llc gpio_ich ppde
v kvm_intel kvm parport_pc i3200_edac serio_raw shpchp edac_core parport lpc_ich mac_hid xgifb(C) 8250_fintek dm_crypt coretemp autofs4 btrfs raid10 raid0 multipath linear raid1
 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq hid_generic usbhid e1000e ahci psmouse libahci ptp hid pps_core
[Wed Aug 19 23:24:01 2015] CPU: 3 PID: 27450 Comm: btrfs-cleaner Tainted: G C 3.19.0-26-generic #27-Ubuntu
[Wed Aug 19 23:24:01 2015] Hardware name: empty empty/TYAN Toledo i3210W/i3200R S5211, BIOS V1.06 09/30/2008
[Wed Aug 19 23:24:01 2015] task: ffff8800eb8475c0 ti: ffff880101df4000 task.ti: ffff880101df4000
[Wed Aug 19 23:24:01 2015] RIP: 0010:[<ffffffffc0553980>] [<ffffffffc0553980>] btrfs_orphan_add+0x1c0/0x1e0 [btrfs]
[Wed Aug 19 23:24:01 2015] RSP: 0018:ffff880101df7c38 EFLAGS: 00010286
[Wed Aug 19 23:24:01 2015] RAX: 00000000ffffffe4 RBX: ffff8800e968e000 RCX: ffff8801a9595000
[Wed Aug 19 23:24:01 2015] RDX: 000000000000ea9a RSI: 0000000000040000 RDI: ffff8801a9595138
[Wed Aug 19 23:24:01 2015] RBP: ffff880101df7c78 R08: 000000000001cef0 R09: ffff8800105f0120
[Wed Aug 19 23:24:01 2015] R10: ffff88020fd9cf30 R11: ffffea0004019340 R12: ffff880002e141a0
[Wed Aug 19 23:24:01 2015] R13: ffff88010072f9a0 R14: ffff8800e968e458 R15: 0000000000000001
[Wed Aug 19 23:24:01 2015] FS: 0000000000000000(0000) GS:ffff88020fd80000(0000) knlGS:0000000000000000
[Wed Aug 19 23:24:01 2015] CS: 0010 DS: 0000 ES: 0000 CR0: 00...

[Colin Ian King (colin-king)]

Seems like this particular issue has been reported here:

http://www.spinics.net/lists/linux-btrfs/msg43084.html

and fixed with upstream fix:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3d84be799194147e04c0e3129ed44a948773b80a

which explains why 4.1-rc2 fixes this issue.

[Colin Ian King (colin-king)]

I've uploaded a test kernel containing the following upstream fix for testing:

commit 3d84be799194147e04c0e3129ed44a948773b80a
Author: Forrest Liu <email address hidden>
Date: Wed Feb 11 14:24:12 2015 +0800

    Btrfs: fix BUG_ON in btrfs_orphan_add() when delete unused block group

The packages can be downloaded from: http://kernel.ubuntu.com/~cking/lp1413008/

Please test these and let me know if it addresses the issue.

[Colin Ian King (colin-king)]

Please test. If no test occurs by August 15th I will close the bug.

[Chris Halse Rogers (raof)]

Just to ensure unambiguous communication: I cannot test, as testing the 4.0-rc7 kernel destroyed the filesystem that exhibited this bug for me.

[Colin Ian King (colin-king)]

Hi Chris, not sure how to proceed with this. Shall we close this now?

[Chris Halse Rogers (raof)]

Yes, unless someone else can reproduce.

I haven't had a filesystem that triggers this since the test kernel which mounted the broken filesystem but destroyed all the data.