Check tree block failed, want=17716610236416, have=0

Discussion:

Zygo Blaxell

2014-10-23 23:16:22 UTC

I attempted to run btrfs check --repair, but it got stuck spinning
in what appeared to be an infinite loop. strace and ltrace revealed
nothing, and gdb wasn't particularly helpful, so I rebuilt btrfs with
debug symbols and tried again.

Now I get this from btrfs check:

Couldn't map the block 17716610236416
No mapping for 17716610236416-17716610252800
Couldn't map the block 17716610236416
Check tree block failed, want=17716610236416, have=0
read block failed check_tree_block
Couldn't read chunk root

Mount fails too:

Oct 23 18:19:38 testhost kernel: [ 388.193783] BTRFS: device label vgs2-md0 devid 3 transid 282186 /dev/dm-11
Oct 23 18:19:38 testhost kernel: [ 388.232892] BTRFS: device label vgs2-md0 devid 1 transid 282186 /dev/mapper/md15
Oct 23 18:19:38 testhost kernel: [ 388.233305] BTRFS: device label vgs2-md0 devid 2 transid 282186 /dev/mapper/md16
Oct 23 18:19:38 testhost kernel: [ 388.234459] BTRFS: device label vgs2-md0 devid 4 transid 282186 /dev/mapper/md18
Oct 23 18:19:38 testhost kernel: [ 388.759456] BTRFS info (device dm-12): disk space caching is enabled
Oct 23 18:19:38 testhost kernel: [ 388.759462] BTRFS: has skinny extents
Oct 23 18:19:38 testhost kernel: [ 388.760576] BTRFS critical (device dm-12): unable to find logical 17716610236416 len 4096
Oct 23 18:19:38 testhost kernel: [ 388.760733] ------------[ cut here ]------------
Oct 23 18:19:38 testhost kernel: [ 388.760807] kernel BUG at fs/btrfs/inode.c:1659!
Oct 23 18:19:38 testhost kernel: [ 388.760880] invalid opcode: 0000 [#1] PREEMPT SMP
Oct 23 18:19:38 testhost kernel: [ 388.761063] Modules linked in: tun cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative softdog nfsd auth_rpcgss nfs_acl nfs lockd fscache sunrpc dummy ipt_MASQUERADE xt_nat xt_tcpudp xt_state iptable_mangle nf_log_ipv4 nf_log_common xt_LOG xt_limit iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack ip6table_filter ip6_tables iptable_filter ip_tables x_tables sch_fq_codel tcp_illinois dm_crypt snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm snd_seq snd_seq_device snd_timer kvm_amd eeepc_wmi snd kvm asus_wmi sparse_keymap rfkill soundcore evdev pcspkr i2c_piix4 parport_pc i2c_core acpi_cpufreq k10temp parport rtc_cmos video processor wmi button thermal_sys k8temp hwmon_vid hwmon btrfs xor raid6_pq dm_mod raid1 md_mod af_packet ipv6 nbd sg uas crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd microc
Oct 23 18:19:38 testhost kernel: ode r8169 mii firmware_class ehci_pci ohci_pci ohci_hcd ehci_hcd
Oct 23 18:19:38 testhost kernel: [ 388.765409] CPU: 0 PID: 25132 Comm: mount Tainted: G W 3.17.1-zb64+ #1
Oct 23 18:19:38 testhost kernel: [ 388.765516] Hardware name: System manufacturer System Product Name/A55BM-E, BIOS 0902 11/14/2013
Oct 23 18:19:38 testhost kernel: [ 388.765625] task: ffff8800a3108000 ti: ffff8804083c8000 task.ti: ffff8804083c8000
Oct 23 18:19:38 testhost kernel: [ 388.765733] RIP: 0010:[<ffffffffc027ea80>] [<ffffffffc027ea80>] btrfs_merge_bio_hook+0x80/0x90 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.765905] RSP: 0018:ffff8804083cb8b8 EFLAGS: 00010282
Oct 23 18:19:38 testhost kernel: [ 388.765979] RAX: 00000000ffffffea RBX: 0000000000001000 RCX: 0000000000000000
Oct 23 18:19:38 testhost kernel: [ 388.766055] RDX: 0000000000000001 RSI: ffffffff8179e4f9 RDI: ffffffff810ca45a
Oct 23 18:19:38 testhost kernel: [ 388.766135] RBP: ffff8804083cb8d8 R08: 0000000000000000 R09: ffff8800000bc1a0
Oct 23 18:19:38 testhost kernel: [ 388.766211] R10: ffff8800000b9cc0 R11: 000000000000b7c0 R12: 0000000000001000
Oct 23 18:19:38 testhost kernel: [ 388.766287] R13: ffff8803f6ca30e8 R14: 000000080e7c2148 R15: ffff8803fae7cbf8
Oct 23 18:19:38 testhost kernel: [ 388.766363] FS: 00007fdb1e9bd800(0000) GS:ffff88041ec00000(0000) knlGS:0000000000000000
Oct 23 18:19:38 testhost kernel: [ 388.766470] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
Oct 23 18:19:38 testhost kernel: [ 388.766544] CR2: 00007fff6ae70ec8 CR3: 00000003feb6c000 CR4: 00000000000407f0
Oct 23 18:19:38 testhost kernel: [ 388.766620] Stack:
Oct 23 18:19:38 testhost kernel: [ 388.766690] ffff8804083cb8d8 0000000000001000 ffff8804083cbb28 0000000000001000
Oct 23 18:19:38 testhost kernel: [ 388.766942] ffff8804083cb938 ffffffffc0299539 ffff8803fae7cbf8 0000002000000000
Oct 23 18:19:38 testhost kernel: [ 388.767193] 0000000000000000 ffffea000df7c2d0 ffff880406cb0330 0000101cf8429000
Oct 23 18:19:38 testhost kernel: [ 388.767444] Call Trace:
Oct 23 18:19:38 testhost kernel: [ 388.767541] [<ffffffffc0299539>] submit_extent_page.isra.34+0x159/0x1f0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767672] [<ffffffffc029af60>] __do_readpage+0x470/0x770 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767770] [<ffffffffc0299ed0>] ? repair_io_failure+0x200/0x200 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767864] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767963] [<ffffffffc0295602>] ? btrfs_lookup_ordered_extent+0x82/0xd0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768093] [<ffffffffc029b320>] __extent_read_full_page+0xc0/0xd0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768188] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768282] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768381] [<ffffffffc029d9d3>] read_extent_buffer_pages+0x253/0x330 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768506] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768601] [<ffffffffc02730c1>] btree_read_extent_buffer_pages.constprop.120+0xb1/0x110 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768728] [<ffffffffc02737aa>] read_tree_block+0x3a/0x60 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768822] [<ffffffffc0277bbd>] open_ctree+0x12cd/0x1f00 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768904] [<ffffffff813c724a>] ? disk_name+0xba/0xc0
Oct 23 18:19:38 testhost kernel: [ 388.768993] [<ffffffffc024d403>] btrfs_mount+0x6d3/0x9a0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.769077] [<ffffffff811c8ec3>] ? alloc_pages_current+0xb3/0x180
Oct 23 18:19:38 testhost kernel: [ 388.769161] [<ffffffff811f6443>] mount_fs+0x43/0x1b0
Oct 23 18:19:38 testhost kernel: [ 388.769240] [<ffffffff81211e24>] vfs_kern_mount+0x74/0x130
Oct 23 18:19:38 testhost kernel: [ 388.769319] [<ffffffff81214292>] do_mount+0x262/0xb40
Oct 23 18:19:38 testhost kernel: [ 388.769397] [<ffffffff8117e56e>] ? __get_free_pages+0xe/0x50
Oct 23 18:19:38 testhost kernel: [ 388.769473] [<ffffffff81213eba>] ? copy_mount_options+0x3a/0x160
Oct 23 18:19:38 testhost kernel: [ 388.769550] [<ffffffff81214e4e>] SyS_mount+0x8e/0xe0
Oct 23 18:19:38 testhost kernel: [ 388.769627] [<ffffffff817a842d>] system_call_fastpath+0x1a/0x1f
Oct 23 18:19:38 testhost kernel: [ 388.769702] Code: c9 45 31 c0 89 fe 48 89 c7 4c 89 65 e8 e8 99 79 02 00 85 c0 78 15 4c 01 e3 31 c0 48 3b 5d e8 0f 97 c0 48 83 c4 10 5b 41 5c 5d c3 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90
Oct 23 18:19:38 testhost kernel: [ 388.772243] RIP [<ffffffffc027ea80>] btrfs_merge_bio_hook+0x80/0x90 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.772373] RSP <ffff8804083cb8b8>
Oct 23 18:19:38 testhost kernel: [ 388.772490] ---[ end trace 40d6c9d5d219b0fe ]---

Before I mkfs and restore, I'd like to try repairing it. Any suggestions?

Robert White

2014-10-24 00:28:58 UTC

Permalink

Is this related to your 5k snapshot drive and your attempt to go back
kernel revs from 3.17.0 etc?

I see that you are using 3.17.1 kernel. Are you also up to the 3.17
version of the btrfs tools?

You may be in deep error land from the long use of 3.10... that said,
the --init-csum-tree or --init-extent-tree options may be your friend
here. The backtrace shows you are in "open_ctree" so the former is more
likely the better bet.

Do make _sure_ you are using a fairly recent (3.14.x at least?) version
of btrfs tools. You might want to download and compile the latest (3.17)
of the tools for this task even if you don't feel comfortable installing
them (without an rpm etc).

Post by Zygo Blaxell
I attempted to run btrfs check --repair, but it got stuck spinning
in what appeared to be an infinite loop. strace and ltrace revealed
nothing, and gdb wasn't particularly helpful, so I rebuilt btrfs with
debug symbols and tried again.
Couldn't map the block 17716610236416
No mapping for 17716610236416-17716610252800
Couldn't map the block 17716610236416
Check tree block failed, want=17716610236416, have=0
read block failed check_tree_block
Couldn't read chunk root
Oct 23 18:19:38 testhost kernel: [ 388.193783] BTRFS: device label vgs2-md0 devid 3 transid 282186 /dev/dm-11
Oct 23 18:19:38 testhost kernel: [ 388.232892] BTRFS: device label vgs2-md0 devid 1 transid 282186 /dev/mapper/md15
Oct 23 18:19:38 testhost kernel: [ 388.233305] BTRFS: device label vgs2-md0 devid 2 transid 282186 /dev/mapper/md16
Oct 23 18:19:38 testhost kernel: [ 388.234459] BTRFS: device label vgs2-md0 devid 4 transid 282186 /dev/mapper/md18
Oct 23 18:19:38 testhost kernel: [ 388.759456] BTRFS info (device dm-12): disk space caching is enabled
Oct 23 18:19:38 testhost kernel: [ 388.759462] BTRFS: has skinny extents
Oct 23 18:19:38 testhost kernel: [ 388.760576] BTRFS critical (device dm-12): unable to find logical 17716610236416 len 4096
Oct 23 18:19:38 testhost kernel: [ 388.760733] ------------[ cut here ]------------
Oct 23 18:19:38 testhost kernel: [ 388.760807] kernel BUG at fs/btrfs/inode.c:1659!
Oct 23 18:19:38 testhost kernel: [ 388.760880] invalid opcode: 0000 [#1] PREEMPT SMP
Oct 23 18:19:38 testhost kernel: [ 388.761063] Modules linked in: tun cpufreq_userspace cpufreq_stats cpufreq_powersave cpufreq_conservative softdog nfsd auth_rpcgss nfs_acl nfs lockd fscache sunrpc dummy ipt_MASQUERADE xt_nat xt_tcpudp xt_state iptable_mangle nf_log_ipv4 nf_log_common xt_LOG xt_limit iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack ip6table_filter ip6_tables iptable_filter ip_tables x_tables sch_fq_codel tcp_illinois dm_crypt snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_pcm snd_seq snd_seq_device snd_timer kvm_amd eeepc_wmi snd kvm asus_wmi sparse_keymap rfkill soundcore evdev pcspkr i2c_piix4 parport_pc i2c_core acpi_cpufreq k10temp parport rtc_cmos video processor wmi button ther

mal_sys k8temp hwmon_vid hwmon btrfs xor raid6_pq dm_mod raid1 md_mod af_packet ipv6 nbd sg uas crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul glue
_helper ablk_helper cryptd microc

Post by Zygo Blaxell
Oct 23 18:19:38 testhost kernel: ode r8169 mii firmware_class ehci_pci ohci_pci ohci_hcd ehci_hcd
Oct 23 18:19:38 testhost kernel: [ 388.765409] CPU: 0 PID: 25132 Comm: mount Tainted: G W 3.17.1-zb64+ #1
Oct 23 18:19:38 testhost kernel: [ 388.765516] Hardware name: System manufacturer System Product Name/A55BM-E, BIOS 0902 11/14/2013
Oct 23 18:19:38 testhost kernel: [ 388.765625] task: ffff8800a3108000 ti: ffff8804083c8000 task.ti: ffff8804083c8000
Oct 23 18:19:38 testhost kernel: [ 388.765733] RIP: 0010:[<ffffffffc027ea80>] [<ffffffffc027ea80>] btrfs_merge_bio_hook+0x80/0x90 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.765905] RSP: 0018:ffff8804083cb8b8 EFLAGS: 00010282
Oct 23 18:19:38 testhost kernel: [ 388.765979] RAX: 00000000ffffffea RBX: 0000000000001000 RCX: 0000000000000000
Oct 23 18:19:38 testhost kernel: [ 388.766055] RDX: 0000000000000001 RSI: ffffffff8179e4f9 RDI: ffffffff810ca45a
Oct 23 18:19:38 testhost kernel: [ 388.766135] RBP: ffff8804083cb8d8 R08: 0000000000000000 R09: ffff8800000bc1a0
Oct 23 18:19:38 testhost kernel: [ 388.766211] R10: ffff8800000b9cc0 R11: 000000000000b7c0 R12: 0000000000001000
Oct 23 18:19:38 testhost kernel: [ 388.766287] R13: ffff8803f6ca30e8 R14: 000000080e7c2148 R15: ffff8803fae7cbf8
Oct 23 18:19:38 testhost kernel: [ 388.766363] FS: 00007fdb1e9bd800(0000) GS:ffff88041ec00000(0000) knlGS:0000000000000000
Oct 23 18:19:38 testhost kernel: [ 388.766470] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
Oct 23 18:19:38 testhost kernel: [ 388.766544] CR2: 00007fff6ae70ec8 CR3: 00000003feb6c000 CR4: 00000000000407f0
Oct 23 18:19:38 testhost kernel: [ 388.766690] ffff8804083cb8d8 0000000000001000 ffff8804083cbb28 0000000000001000
Oct 23 18:19:38 testhost kernel: [ 388.766942] ffff8804083cb938 ffffffffc0299539 ffff8803fae7cbf8 0000002000000000
Oct 23 18:19:38 testhost kernel: [ 388.767193] 0000000000000000 ffffea000df7c2d0 ffff880406cb0330 0000101cf8429000
Oct 23 18:19:38 testhost kernel: [ 388.767541] [<ffffffffc0299539>] submit_extent_page.isra.34+0x159/0x1f0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767672] [<ffffffffc029af60>] __do_readpage+0x470/0x770 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767770] [<ffffffffc0299ed0>] ? repair_io_failure+0x200/0x200 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767864] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.767963] [<ffffffffc0295602>] ? btrfs_lookup_ordered_extent+0x82/0xd0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768093] [<ffffffffc029b320>] __extent_read_full_page+0xc0/0xd0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768188] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768282] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768381] [<ffffffffc029d9d3>] read_extent_buffer_pages+0x253/0x330 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768506] [<ffffffffc0271310>] ? verify_parent_transid+0x210/0x210 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768601] [<ffffffffc02730c1>] btree_read_extent_buffer_pages.constprop.120+0xb1/0x110 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768728] [<ffffffffc02737aa>] read_tree_block+0x3a/0x60 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768822] [<ffffffffc0277bbd>] open_ctree+0x12cd/0x1f00 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.768904] [<ffffffff813c724a>] ? disk_name+0xba/0xc0
Oct 23 18:19:38 testhost kernel: [ 388.768993] [<ffffffffc024d403>] btrfs_mount+0x6d3/0x9a0 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.769077] [<ffffffff811c8ec3>] ? alloc_pages_current+0xb3/0x180
Oct 23 18:19:38 testhost kernel: [ 388.769161] [<ffffffff811f6443>] mount_fs+0x43/0x1b0
Oct 23 18:19:38 testhost kernel: [ 388.769240] [<ffffffff81211e24>] vfs_kern_mount+0x74/0x130
Oct 23 18:19:38 testhost kernel: [ 388.769319] [<ffffffff81214292>] do_mount+0x262/0xb40
Oct 23 18:19:38 testhost kernel: [ 388.769397] [<ffffffff8117e56e>] ? __get_free_pages+0xe/0x50
Oct 23 18:19:38 testhost kernel: [ 388.769473] [<ffffffff81213eba>] ? copy_mount_options+0x3a/0x160
Oct 23 18:19:38 testhost kernel: [ 388.769550] [<ffffffff81214e4e>] SyS_mount+0x8e/0xe0
Oct 23 18:19:38 testhost kernel: [ 388.769627] [<ffffffff817a842d>] system_call_fastpath+0x1a/0x1f
Oct 23 18:19:38 testhost kernel: [ 388.769702] Code: c9 45 31 c0 89 fe 48 89 c7 4c 89 65 e8 e8 99 79 02 00 85 c0 78 15 4c 01 e3 31 c0 48 3b 5d e8 0f 97 c0 48 83 c4 10 5b 41 5c 5d c3 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90
Oct 23 18:19:38 testhost kernel: [ 388.772243] RIP [<ffffffffc027ea80>] btrfs_merge_bio_hook+0x80/0x90 [btrfs]
Oct 23 18:19:38 testhost kernel: [ 388.772373] RSP <ffff8804083cb8b8>
Oct 23 18:19:38 testhost kernel: [ 388.772490] ---[ end trace 40d6c9d5d219b0fe ]---
Before I mkfs and restore, I'd like to try repairing it. Any suggestions?

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Zygo Blaxell

2014-10-24 01:24:48 UTC

Permalink

Post by Robert White
Is this related to your 5k snapshot drive and your attempt to go
back kernel revs from 3.17.0 etc?

This filesystem has four subvolumes: a mostly empty root subvolume,
one containing ~13TB of data, and two read-write snapshot subvolumes
taken from the big data subvolume.

I have a dozen or so btrfs filesystems representing a variety of
workloads. One of them blows up about once a week, usually due to
some bug that was fixed a few days before. :-/

Post by Robert White
I see that you are using 3.17.1 kernel. Are you also up to the 3.17
version of the btrfs tools?

I was running tools 3.16.2, but I'll build 3.17 now that I found the
git repo it lives in. :-P

Post by Robert White
You may be in deep error land from the long use of 3.10... that
said, the --init-csum-tree or --init-extent-tree options may be your
friend here. The backtrace shows you are in "open_ctree" so the
former is more likely the better bet.

This filesystem was built on 3.12 or 3.14. I build stable kernels the
same day they come out, so this machine is reasonably up to date.

Now that I think about it, my 3.17.1-zb64 kernel also has these commits
in it:

d379730 Revert "Btrfs: race free update of commit root for ro snapshots"
4238302 Btrfs: fix race in WAIT_SYNC ioctl
75bfb9a Btrfs: cleanup error handling in build_backref_tree
bbe9051 Btrfs: fix build_backref_tree issue with multiple shared blocks
32be3a1 btrfs: Fix the wrong condition judgment about subset extent map
1d52c78 Btrfs: try not to ENOSPC on log replay
f6acfd5 Btrfs: don't do async reclaim during log replay
e6c4efd btrfs: Fix and enhance merge_extent_mapping() to insert best fitted extent map
4d1a40c Btrfs: fix up bounds checking in lseek
78a017a Btrfs: add missing compression property remove in btrfs_ioctl_setflags
12b894c btrfs: Fix a deadlock in btrfs_dev_replace_finishing()
0b4699d btrfs: don't go readonly on existing qgroup items
2fad4e8 btrfs: wake up transaction thread from SYNC_FS ioctl

These came from a list posted by Chris recently for the stable kernels.

Post by Robert White
Do make _sure_ you are using a fairly recent (3.14.x at least?)
version of btrfs tools. You might want to download and compile the
latest (3.17) of the tools for this task even if you don't feel
comfortable installing them (without an rpm etc).

e
_helper ablk_helper cryptd microc

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Zygo Blaxell

2014-10-24 02:05:50 UTC

Permalink

Alas, both fail:

# btrfs check --repair --init-csum-tree --init-extent-tree /dev/mapper/md15
enabling repair mode
Creating a new CRC tree
Couldn't open file system

Same result with each option individually, except that when
--init-csum-tree is absent, so is the "Creating a new CRC tree" message.

I'm also trying 'btrfs rescue chunk-recover -v' but so far it has read
many gigabytes but not had much to say.

(LVM snapshots + kvm = attack this filesystem with multiple tools at once :-)