The stack trace for i386 failure is 
Jun 28 13:06:55 kernel: [  196.197710] Kernel BUG at c12094bc [verbose debug info unavailable]
Jun 28 13:06:55 kernel: [  196.197713] invalid opcode: 0000 [#1] SMP 
Jun 28 13:06:55 kernel: [  196.197716] Modules linked in: squashfs(F) xfs(F) reiserfs jfs btrfs(F) xor(F) zlib_deflate(F) raid6_pq(F) libcrc32c(F) ext2(F) virtio_balloon(F) nls_utf8(F) isofs(F) usb_storage(F) vga16fb(F) vgastate(F) floppy(F)
Jun 28 13:06:55 kernel: [  196.197727] CPU: 0 PID: 31522 Comm: in-target Tainted: GF            3.10.0-0-generic #7-Ubuntu
Jun 28 13:06:55 kernel: [  196.197729] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
Jun 28 13:06:55 kernel: [  196.197731] task: ddec4d40 ti: d36aa000 task.ti: d36aa000
Jun 28 13:06:55 kernel: [  196.197734] EIP: 0060:[<c12094bc>] EFLAGS: 00010202 CPU: 0
Jun 28 13:06:55 kernel: [  196.197751] EIP is at ext4_mb_release_group_pa+0x10c/0x110
Jun 28 13:06:55 kernel: [  196.197753] EAX: 00000001 EBX: d6a1c580 ECX: 00000015 EDX: 00000000
Jun 28 13:06:55 kernel: [  196.197754] ESI: d3fba240 EDI: d3fba240 EBP: d36abb30 ESP: d36abb04
Jun 28 13:06:55 kernel: [  196.197756]  DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Jun 28 13:06:55 kernel: [  196.197758] CR0: 80050033 CR2: b76140f2 CR3: 019f7000 CR4: 000006b0
Jun 28 13:06:55 kernel: [  196.197765] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
Jun 28 13:06:55 kernel: [  196.197768] DR6: ffff0ff0 DR7: 00000400
Jun 28 13:06:55 kernel: [  196.197770] Stack:
Jun 28 13:06:55 kernel: [  196.197771]  d36abb1c d36abb20 d36abb30 c1208922 d36abb74 ddadf000 00000015 00001fff
Jun 28 13:06:55 kernel: [  196.197775]  d6a1c580 d3fba240 ddadf000 d36abba0 c12096af d4c09230 00000000 00000000
Jun 28 13:06:55 kernel: [  196.197779]  dd2987e0 ddadf400 dd121040 dd2987e0 d36abb74 00000016 d3fba250 d3fba3a8
Jun 28 13:06:55 kernel: [  196.197783] Call Trace:
Jun 28 13:06:55 kernel: [  196.197788]  [<c1208922>] ? ext4_mb_load_buddy+0x212/0x2f0
Jun 28 13:06:55 kernel: [  196.197792]  [<c12096af>] ext4_mb_discard_lg_preallocations+0x1ef/0x2d0
Jun 28 13:06:55 kernel: [  196.197795]  [<c1209ba6>] ext4_mb_release_context+0x416/0x4f0
Jun 28 13:06:55 kernel: [  196.197799]  [<c120c749>] ext4_mb_new_blocks+0x309/0x560
Jun 28 13:06:55 kernel: [  196.197802]  [<c12034de>] ext4_ext_map_blocks+0x9ee/0xf10
Jun 28 13:06:55 kernel: [  196.197808]  [<c1223db9>] ? jbd2_journal_get_write_access+0x29/0x30
Jun 28 13:06:55 kernel: [  196.197814]  [<c11dd819>] ? ext4_mark_iloc_dirty+0x3c9/0x5a0
Jun 28 13:06:55 kernel: [  196.197818]  [<c11db555>] ext4_map_blocks+0x2b5/0x4d0
Jun 28 13:06:55 kernel: [  196.197830]  [<c1108b82>] ? find_get_pages_tag+0xb2/0x150
Jun 28 13:06:55 kernel: [  196.197834]  [<c11ddd40>] mpage_da_map_and_submit+0x120/0x5c0
Jun 28 13:06:55 kernel: [  196.197838]  [<c12048bd>] ? __ext4_journal_start_sb+0x6d/0x130
Jun 28 13:06:55 kernel: [  196.197841]  [<c11de8a8>] ext4_da_writepages+0x2b8/0x550
Jun 28 13:06:55 kernel: [  196.197845]  [<c1111d9a>] do_writepages+0x1a/0x40
Jun 28 13:06:55 kernel: [  196.197848]  [<c1109814>] __filemap_fdatawrite_range+0x54/0x60
Jun 28 13:06:55 kernel: [  196.197850]  [<c11098eb>] filemap_flush+0x2b/0x30
Jun 28 13:06:55 kernel: [  196.197853]  [<c11dbc8f>] ext4_alloc_da_blocks+0x2f/0x60
Jun 28 13:06:55 kernel: [  196.197856]  [<c11d5842>] ext4_release_file+0x62/0xa0
Jun 28 13:06:55 kernel: [  196.197863]  [<c115a153>] __fput+0xc3/0x1f0
Jun 28 13:06:55 kernel: [  196.197866]  [<c115a32d>] ____fput+0xd/0x10
Jun 28 13:06:55 kernel: [  196.197874]  [<c1065471>] task_work_run+0xb1/0xd0
Jun 28 13:06:55 kernel: [  196.197879]  [<c104cafd>] do_exit+0x25d/0x8d0
Jun 28 13:06:55 kernel: [  196.197881]  [<c1158630>] ? default_llseek+0x170/0x170
Jun 28 13:06:55 kernel: [  196.197884]  [<c104b260>] ? task_stopped_code+0x50/0x50
Jun 28 13:06:55 kernel: [  196.197887]  [<c104d1e4>] do_group_exit+0x34/0xa0
Jun 28 13:06:55 kernel: [  196.197892]  [<c1610040>] ? arch_prepare_kprobe_ftrace+0x20/0x20
Jun 28 13:06:55 kernel: [  196.197894]  [<c104d266>] SyS_exit_group+0x16/0x20
Jun 28 13:06:55 kernel: [  196.197898]  [<c161418d>] sysenter_do_call+0x12/0x28
Jun 28 13:06:55 kernel: [  196.197899] Code: 24 04 8b 55 e8 89 4c 24 08 31 c9 ff d6 8b 33 85 f6 75 dc 83 c4 20 31 c0 5b 5e 5f 5d c3 8b 47 30 85 c0 75 07 31 d2 e9 4a ff ff ff <0f> 0b 66 90 55 89 e5 57 56 53 83 ec 5c 3e 8d 74 26 00 89 c7 89
Jun 28 13:06:55 kernel: [  196.197922] EIP: [<c12094bc>] ext4_mb_release_group_pa+0x10c/0x110 SS:ESP 0068:d36abb04
Jun 28 13:06:55 kernel: [  196.197930] ---[ end trace d939e92aebff63ab ]---
Jun 28 13:06:55 kernel: [  196.197932] Fixing recursive fault but reboot is needed!