Comment 2 for bug 1413008

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 ]---