[  579.578508] perf interrupt took too long (2507 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
[  600.236051] INFO: task kworker/u16:1:68 blocked for more than 120 seconds.
[  600.236060]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236062] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236064] kworker/u16:1   D ffff88085b627c30     0    68      2 0x00000000
[  600.236118] Workqueue: btrfs-qgroup-rescan btrfs_qgroup_rescan_helper [btrfs]
[  600.236120]  ffff88085b627c30 ffff880823eae0e0 ffff88085bfc8000 ffff88085bbc6600
[  600.236122]  ffff88085b628000 ffff8808545351f0 ffff880854535000 ffff8808545351f0
[  600.236124]  0000000000000001 ffff88085b627c48 ffffffff817f8f55 ffff880857bb01b0
[  600.236126] Call Trace:
[  600.236133]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236144]  [<ffffffffc03abb73>] wait_current_trans.isra.21+0xd3/0x120 [btrfs]
[  600.236148]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236159]  [<ffffffffc03ad44b>] start_transaction+0x2cb/0x4a0 [btrfs]
[  600.236170]  [<ffffffffc03ad638>] btrfs_start_transaction+0x18/0x20 [btrfs]
[  600.236183]  [<ffffffffc0413c18>] btrfs_qgroup_rescan_worker+0x88/0x550 [btrfs]
[  600.236186]  [<ffffffff8101566c>] ? __switch_to+0x1dc/0x5a0
[  600.236198]  [<ffffffffc03de70a>] btrfs_scrubparity_helper+0xca/0x290 [btrfs]
[  600.236210]  [<ffffffffc03de91e>] btrfs_qgroup_rescan_helper+0xe/0x10 [btrfs]
[  600.236213]  [<ffffffff8109687a>] process_one_work+0x1aa/0x440
[  600.236215]  [<ffffffff81096b5b>] worker_thread+0x4b/0x4c0
[  600.236217]  [<ffffffff81096b10>] ? process_one_work+0x440/0x440
[  600.236219]  [<ffffffff8109ccd8>] kthread+0xd8/0xf0
[  600.236221]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236224]  [<ffffffff817fd38f>] ret_from_fork+0x3f/0x70
[  600.236226]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236259] INFO: task kworker/u16:8:1575 blocked for more than 120 seconds.
[  600.236260]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236261] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236262] kworker/u16:8   D ffff8808590d7cd0     0  1575      2 0x00000000
[  600.236277] Workqueue: btrfs-extent-refs btrfs_extent_refs_helper [btrfs]
[  600.236278]  ffff8808590d7cd0 ffffffff8118ac69 ffff88085bfc8000 ffff88085886f2c0
[  600.236280]  ffff8808590d8000 ffff880856e9e9f0 ffff880856e9e800 ffff880856e9e9f0
[  600.236282]  0000000000000001 ffff8808590d7ce8 ffffffff817f8f55 ffff880857bb01b0
[  600.236284] Call Trace:
[  600.236288]  [<ffffffff8118ac69>] ? mempool_free+0x29/0x80
[  600.236290]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236300]  [<ffffffffc03abb73>] wait_current_trans.isra.21+0xd3/0x120 [btrfs]
[  600.236302]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236313]  [<ffffffffc03ad3fb>] start_transaction+0x27b/0x4a0 [btrfs]
[  600.236324]  [<ffffffffc03ad677>] btrfs_join_transaction+0x17/0x20 [btrfs]
[  600.236333]  [<ffffffffc0397988>] delayed_ref_async_start+0x18/0x90 [btrfs]
[  600.236345]  [<ffffffffc03de70a>] btrfs_scrubparity_helper+0xca/0x290 [btrfs]
[  600.236357]  [<ffffffffc03de90e>] btrfs_extent_refs_helper+0xe/0x10 [btrfs]
[  600.236359]  [<ffffffff8109687a>] process_one_work+0x1aa/0x440
[  600.236361]  [<ffffffff81096b5b>] worker_thread+0x4b/0x4c0
[  600.236362]  [<ffffffff81096b10>] ? process_one_work+0x440/0x440
[  600.236364]  [<ffffffff81096b10>] ? process_one_work+0x440/0x440
[  600.236366]  [<ffffffff8109ccd8>] kthread+0xd8/0xf0
[  600.236368]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236369]  [<ffffffff817fd38f>] ret_from_fork+0x3f/0x70
[  600.236371]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236413] INFO: task btrfs-cleaner:2912 blocked for more than 120 seconds.
[  600.236414]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236415] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236416] btrfs-cleaner   D ffff88081d1ebc08     0  2912      2 0x00000000
[  600.236419]  ffff88081d1ebc08 ffffffff810ad7a7 ffff88085bfccc80 ffff880826c80000
[  600.236421]  ffff88081d1ec000 ffff880834e10920 ffff880834e10918 ffff880826c80000
[  600.236422]  ffff880859689500 ffff88081d1ebc20 ffffffff817f8f55 7fffffffffffffff
[  600.236424] Call Trace:
[  600.236427]  [<ffffffff810ad7a7>] ? sched_clock_local+0x17/0x80
[  600.236429]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236431]  [<ffffffff817fc049>] schedule_timeout+0x189/0x250
[  600.236433]  [<ffffffff810a83a5>] ? wake_up_process+0x15/0x20
[  600.236434]  [<ffffffff81094901>] ? insert_work+0x81/0xc0
[  600.236436]  [<ffffffff810a8067>] ? try_to_wake_up+0x47/0x370
[  600.236438]  [<ffffffff817f99b3>] wait_for_completion+0xb3/0x140
[  600.236439]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.236449]  [<ffffffffc0391c17>] btrfs_async_run_delayed_refs+0x127/0x150 [btrfs]
[  600.236460]  [<ffffffffc03ad927>] __btrfs_end_transaction+0x1f7/0x340 [btrfs]
[  600.236471]  [<ffffffffc03ade93>] btrfs_end_transaction_throttle+0x13/0x20 [btrfs]
[  600.236481]  [<ffffffffc0395fb9>] btrfs_drop_snapshot+0x539/0x830 [btrfs]
[  600.236492]  [<ffffffffc03ac672>] btrfs_clean_one_deleted_snapshot+0xb2/0x100 [btrfs]
[  600.236502]  [<ffffffffc03a4ffe>] cleaner_kthread+0xae/0x200 [btrfs]
[  600.236512]  [<ffffffffc03a4f50>] ? check_leaf+0x360/0x360 [btrfs]
[  600.236514]  [<ffffffff8109ccd8>] kthread+0xd8/0xf0
[  600.236516]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236518]  [<ffffffff817fd38f>] ret_from_fork+0x3f/0x70
[  600.236520]  [<ffffffff8109cc00>] ? kthread_create_on_node+0x1a0/0x1a0
[  600.236522] INFO: task btrfs:2967 blocked for more than 120 seconds.
[  600.236523]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236524] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236525] btrfs           D ffff88081a8d7af8     0  2967   1974 0x00000000
[  600.236527]  ffff88081a8d7af8 ffffffff810a8420 ffff88085bfccc80 ffff880834c0a640
[  600.236529]  ffff88081a8d8000 ffff880857bb0230 ffff88082ad10200 000000000006e615
[  600.236531]  ffff88082916e360 ffff88081a8d7b10 ffffffff817f8f55 ffff880857bb01b0
[  600.236533] Call Trace:
[  600.236535]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.236536]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236547]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.236549]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236560]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.236570]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.236581]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.236583]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.236596]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.236608]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.236611]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.236623]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.236625]  [<ffffffff810ad976>] ? sched_clock_cpu+0x46/0xa0
[  600.236627]  [<ffffffff810a74d4>] ? check_preempt_curr+0x54/0x90
[  600.236628]  [<ffffffff810a7529>] ? ttwu_do_wakeup+0x19/0xc0
[  600.236630]  [<ffffffff810a766d>] ? ttwu_do_activate.constprop.89+0x5d/0x70
[  600.236631]  [<ffffffff810a8067>] ? try_to_wake_up+0x47/0x370
[  600.236633]  [<ffffffff810a83a5>] ? wake_up_process+0x15/0x20
[  600.236635]  [<ffffffff810c7ffd>] ? __rwsem_do_wake+0x10d/0x140
[  600.236638]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.236642]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.236645]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.236647]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.236650]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.236652]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.236654]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.236656] INFO: task btrfs:2968 blocked for more than 120 seconds.
[  600.236657]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236658] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236659] btrfs           D ffff88081a863af8     0  2968   1974 0x00000000
[  600.236661]  ffff88081a863af8 ffffffff810a8420 ffff88085bfc9980 ffff880834c0f2c0
[  600.236663]  ffff88081a864000 ffff880857bb0230 ffff88082ad11000 000000000006e615
[  600.236665]  ffff880857b8f510 ffff88081a863b10 ffffffff817f8f55 ffff880857bb01b0
[  600.236667] Call Trace:
[  600.236668]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.236670]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236680]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.236682]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236693]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.236703]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.236714]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.236716]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.236728]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.236740]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.236742]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.236754]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.236756]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.236758]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.236760]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.236761]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.236763]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.236765]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.236767]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.236769] INFO: task btrfs:2969 blocked for more than 120 seconds.
[  600.236770]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236771] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236772] btrfs           D ffff88081a867af8     0  2969   1974 0x00000000
[  600.236774]  ffff88081a867af8 ffffffff810a8420 ffffffff81e11500 ffff880826c4b300
[  600.236776]  ffff88081a868000 ffff880857bb0230 ffff88082ad11000 000000000006e615
[  600.236778]  ffff88081ba6d510 ffff88081a867b10 ffffffff817f8f55 ffff880857bb01b0
[  600.236780] Call Trace:
[  600.236782]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.236783]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236794]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.236796]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236806]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.236816]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.236828]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.236830]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.236841]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.236853]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.236855]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.236867]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.236869]  [<ffffffff811e5abb>] ? __slab_free+0xcb/0x2c0
[  600.236871]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.236873]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.236875]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.236876]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.236878]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.236880]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.236882]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.236884] INFO: task btrfs:2970 blocked for more than 120 seconds.
[  600.236885]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236886] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236887] btrfs           D ffff88081a8e3af8     0  2970   1974 0x00000000
[  600.236889]  ffff88081a8e3af8 ffffffff810a8420 ffff88085bfca640 ffff880826c4e600
[  600.236891]  ffff88081a8e4000 ffff880857bb0230 ffff88082ad11000 000000000006e615
[  600.236893]  ffff88081ba6df30 ffff88081a8e3b10 ffffffff817f8f55 ffff880857bb01b0
[  600.236895] Call Trace:
[  600.236896]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.236898]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.236908]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.236910]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.236921]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.236930]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.236942]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.236944]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.236956]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.236967]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.236969]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.236981]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.236983]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.236985]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.236987]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.236989]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.236991]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.236993]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.236994]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.236996] INFO: task btrfs:2971 blocked for more than 120 seconds.
[  600.236997]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.236998] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.236999] btrfs           D ffff88081a8e7af8     0  2971   1974 0x00000000
[  600.237001]  ffff88081a8e7af8 ffffffff810a8420 ffffffff81e11500 ffff880826c4d940
[  600.237003]  ffff88081a8e8000 ffff880857bb0230 ffff88082ad11000 000000000006e615
[  600.237005]  ffff88007b243f30 ffff88081a8e7b10 ffffffff817f8f55 ffff880857bb01b0
[  600.237007] Call Trace:
[  600.237009]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.237010]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.237021]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.237023]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.237034]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.237043]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.237055]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.237057]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.237069]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.237080]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.237082]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.237094]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.237096]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.237098]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.237100]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.237102]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.237104]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.237105]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.237107]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.237109] INFO: task btrfs:2972 blocked for more than 120 seconds.
[  600.237110]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.237111] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.237112] btrfs           D ffff88081a8ebaf8     0  2972   1974 0x00000000
[  600.237114]  ffff88081a8ebaf8 ffffffff810a8420 ffffffff81e11500 ffff880826c4f2c0
[  600.237116]  ffff88081a8ec000 ffff880857bb0230 ffff88082ad11000 000000000006e615
[  600.237118]  ffff88081b95fea0 ffff88081a8ebb10 ffffffff817f8f55 ffff880857bb01b0
[  600.237120] Call Trace:
[  600.237122]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.237123]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.237134]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.237136]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.237146]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.237156]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.237168]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.237170]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.237182]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.237193]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.237195]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.237207]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.237209]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.237211]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.237213]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.237215]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.237217]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.237218]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.237220]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75
[  600.237222] INFO: task btrfs:2973 blocked for more than 120 seconds.
[  600.237223]       Not tainted 4.4.0-040400rc6-generic #201512202030
[  600.237224] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  600.237225] btrfs           D ffff88081a8efaf8     0  2973   1974 0x00000000
[  600.237227]  ffff88081a8efaf8 ffffffff810a8420 ffff88085bfccc80 ffff880826c48cc0
[  600.237230]  ffff88081a8f0000 ffff880857bb0230 ffff88081d7c9e00 000000000006e615
[  600.237232]  ffff88007b243630 ffff88081a8efb10 ffffffff817f8f55 ffff880857bb01b0
[  600.237233] Call Trace:
[  600.237235]  [<ffffffff810a8420>] ? wake_up_q+0x70/0x70
[  600.237236]  [<ffffffff817f8f55>] schedule+0x35/0x80
[  600.237247]  [<ffffffffc03ab972>] wait_for_commit.isra.16+0x52/0xa0 [btrfs]
[  600.237249]  [<ffffffff810bfec0>] ? wake_atomic_t_function+0x60/0x60
[  600.237259]  [<ffffffffc03ac0e5>] btrfs_wait_for_commit+0x145/0x170 [btrfs]
[  600.237269]  [<ffffffffc039b257>] btrfs_inc_block_group_ro+0x67/0x1b0 [btrfs]
[  600.237281]  [<ffffffffc040a2df>] scrub_enumerate_chunks+0x21f/0x580 [btrfs]
[  600.237283]  [<ffffffff810bfe00>] ? prepare_to_wait_event+0x90/0xf0
[  600.237295]  [<ffffffffc040b95c>] btrfs_scrub_dev+0x1bc/0x530 [btrfs]
[  600.237306]  [<ffffffffc03e5ff7>] ? btrfs_ioctl+0xdf7/0x2850 [btrfs]
[  600.237308]  [<ffffffff812265f6>] ? __mnt_want_write+0x56/0x60
[  600.237320]  [<ffffffffc03e6c97>] btrfs_ioctl+0x1a97/0x2850 [btrfs]
[  600.237327]  [<ffffffff811e55cb>] ? kmem_cache_alloc_node+0xbb/0x1f0
[  600.237329]  [<ffffffff8139f2c3>] ? create_task_io_context+0x23/0x100
[  600.237331]  [<ffffffff812192a8>] do_vfs_ioctl+0x298/0x480
[  600.237333]  [<ffffffff8139f3e6>] ? get_task_io_context+0x46/0x90
[  600.237335]  [<ffffffff813ad98c>] ? set_task_ioprio+0x8c/0xa0
[  600.237336]  [<ffffffff81219509>] SyS_ioctl+0x79/0x90
[  600.237338]  [<ffffffff817fcff6>] entry_SYSCALL_64_fastpath+0x16/0x75