Got some more stack traces: 

[22201.670647] INFO: task mongod:1917 blocked for more than 120 seconds.
[22201.670650]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[22201.670651] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[22201.670653] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[22201.670655]  ffff8805aecefba8 00000000579b1d9a ffff8807faf06040 ffff8806d6238000
[22201.670657]  ffff8805aecf0000 ffff88081edd6d00 7fffffffffffffff ffffffff8182a610
[22201.670659]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[22201.670661] Call Trace:
[22201.670666]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[22201.670668]  [<ffffffff81829e15>] schedule+0x35/0x80
[22201.670670]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[22201.670673]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[22201.670675]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[22201.670676]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[22201.670678]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[22201.670680]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[22201.670682]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[22201.670684]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[22201.670686]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[22201.670688]  [<ffffffff8118ef91>] ? __filemap_fdatawrite_range+0xd1/0x100
[22201.670690]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[22201.670691]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[22201.670732]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[22201.670734]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[22201.670736]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[22201.670738]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[85684.344389] INFO: task mongod:1917 blocked for more than 120 seconds.
[85684.344393]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[85684.344394] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[85684.344395] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[85684.344398]  ffff8805aecefba8 0000000000000003 ffffffff81e11500 ffff8806d6238000
[85684.344400]  ffff8805aecf0000 ffff88081ec16d00 7fffffffffffffff ffffffff8182a610
[85684.344402]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[85684.344403] Call Trace:
[85684.344409]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[85684.344411]  [<ffffffff81829e15>] schedule+0x35/0x80
[85684.344413]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[85684.344416]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[85684.344418]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[85684.344419]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[85684.344421]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[85684.344423]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[85684.344425]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[85684.344427]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[85684.344429]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[85684.344431]  [<ffffffff8118ef91>] ? __filemap_fdatawrite_range+0xd1/0x100
[85684.344432]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[85684.344434]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[85684.344477]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[85684.344479]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[85684.344481]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[85684.344483]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[110165.396049] INFO: task mongod:1917 blocked for more than 120 seconds.
[110165.396053]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[110165.396054] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[110165.396055] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[110165.396058]  ffff8805aecefba8 00000000579c74f7 ffff8807faf02940 ffff8806d6238000
[110165.396060]  ffff8805aecf0000 ffff88081ecd6d00 7fffffffffffffff ffffffff8182a610
[110165.396062]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[110165.396064] Call Trace:
[110165.396070]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[110165.396072]  [<ffffffff81829e15>] schedule+0x35/0x80
[110165.396074]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[110165.396076]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[110165.396078]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[110165.396080]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[110165.396082]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[110165.396083]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[110165.396085]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[110165.396088]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[110165.396090]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[110165.396091]  [<ffffffff8118ef91>] ? __filemap_fdatawrite_range+0xd1/0x100
[110165.396093]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[110165.396094]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[110165.396137]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[110165.396139]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[110165.396141]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[110165.396143]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[132726.355047] INFO: task mongod:1917 blocked for more than 120 seconds.
[132726.355062]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[132726.355063] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[132726.355065] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[132726.355067]  ffff8805aecefba8 0000000000000003 ffff8806d623e040 ffff8806d6238000
[132726.355069]  ffff8805aecf0000 ffff88081ed56d00 7fffffffffffffff ffffffff8182a610
[132726.355071]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[132726.355073] Call Trace:
[132726.355079]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[132726.355081]  [<ffffffff81829e15>] schedule+0x35/0x80
[132726.355082]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[132726.355085]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[132726.355087]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[132726.355089]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[132726.355091]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[132726.355092]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[132726.355094]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[132726.355097]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[132726.355099]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[132726.355101]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[132726.355102]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[132726.355143]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[132726.355146]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[132726.355148]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[132726.355150]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[152887.214613] INFO: task mongod:1917 blocked for more than 120 seconds.
[152887.214617]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[152887.214618] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[152887.214619] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[152887.214622]  ffff8805aecefba8 00000000579d1c18 ffff8807faf01b80 ffff8806d6238000
[152887.214624]  ffff8805aecf0000 ffff88081ec96d00 7fffffffffffffff ffffffff8182a610
[152887.214626]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[152887.214628] Call Trace:
[152887.214634]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[152887.214636]  [<ffffffff81829e15>] schedule+0x35/0x80
[152887.214637]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[152887.214640]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[152887.214642]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[152887.214644]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[152887.214646]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[152887.214647]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[152887.214649]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[152887.214652]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[152887.214654]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[152887.214656]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[152887.214657]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[152887.214698]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[152887.214700]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[152887.214703]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[152887.214704]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[170287.952597] INFO: task txg_sync:4602 blocked for more than 120 seconds.
[170287.952600]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[170287.952602] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[170287.952603] txg_sync        D ffff8800d95c3aa8     0  4602      2 0x00000000
[170287.952606]  ffff8800d95c3aa8 ffff88081edd6d00 ffff8807faf06040 ffff8807f627ee00
[170287.952608]  ffff8800d95c4000 ffff88081edd6d00 7fffffffffffffff ffff88017c6cc0a8
[170287.952610]  0000000000000001 ffff8800d95c3ac0 ffffffff81829e15 0000000000000000
[170287.952611] Call Trace:
[170287.952617]  [<ffffffff81829e15>] schedule+0x35/0x80
[170287.952619]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[170287.952621]  [<ffffffff810ba44c>] ? set_next_entity+0x9c/0xb0
[170287.952624]  [<ffffffff8102d66c>] ? __switch_to+0x1dc/0x5c0
[170287.952626]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[170287.952633]  [<ffffffffc07b4bec>] cv_wait_common+0xbc/0x140 [spl]
[170287.952635]  [<ffffffff810c3ca0>] ? wake_atomic_t_function+0x60/0x60
[170287.952640]  [<ffffffffc07b4cc8>] __cv_wait_io+0x18/0x20 [spl]
[170287.952683]  [<ffffffffc08f22fe>] zio_wait+0x10e/0x1f0 [zfs]
[170287.952704]  [<ffffffffc087bc58>] dsl_pool_sync+0xb8/0x430 [zfs]
[170287.952726]  [<ffffffffc08975b6>] spa_sync+0x366/0xb30 [zfs]
[170287.952729]  [<ffffffff810ac0c2>] ? default_wake_function+0x12/0x20
[170287.952753]  [<ffffffffc08a8a4a>] txg_sync_thread+0x3ba/0x630 [zfs]
[170287.952778]  [<ffffffffc08a8690>] ? txg_delay+0x180/0x180 [zfs]
[170287.952782]  [<ffffffffc07afe31>] thread_generic_wrapper+0x71/0x80 [spl]
[170287.952785]  [<ffffffffc07afdc0>] ? __thread_exit+0x20/0x20 [spl]
[170287.952787]  [<ffffffff810a0808>] kthread+0xd8/0xf0
[170287.952789]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
[170287.952791]  [<ffffffff8182e28f>] ret_from_fork+0x3f/0x70
[170287.952792]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
[170287.952873] INFO: task mongod:1917 blocked for more than 120 seconds.
[170287.952874]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[170287.952875] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[170287.952876] mongod          D ffff8805aecefaa8     0  1917   5819 0x00000100
[170287.952877]  ffff8805aecefaa8 ffff8805aecefa80 ffff8807faf05280 ffff8806d6238000
[170287.952879]  ffff8805aecf0000 ffff88081ed96d00 7fffffffffffffff ffffffff8182a610
[170287.952881]  ffff8805aecefc08 ffff8805aecefac0 ffffffff81829e15 0000000000000000
[170287.952882] Call Trace:
[170287.952884]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[170287.952886]  [<ffffffff81829e15>] schedule+0x35/0x80
[170287.952887]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[170287.952910]  [<ffffffffc088d478>] ? rrm_exit+0x48/0x80 [zfs]
[170287.952937]  [<ffffffffc08e42f4>] ? zfs_putpage+0x524/0x560 [zfs]
[170287.952939]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[170287.952941]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[170287.952942]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[170287.952944]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[170287.952950]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[170287.952951]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[170287.952954]  [<ffffffff811998d2>] write_cache_pages+0x392/0x510
[170287.952981]  [<ffffffffc08f7a20>] ? zpl_write_common_iovec+0xe0/0xe0 [zfs]
[170287.952982]  [<ffffffff8182bd82>] ? mutex_lock+0x12/0x30
[170287.953004]  [<ffffffffc088d130>] ? rrw_exit+0x60/0x150 [zfs]
[170287.953031]  [<ffffffffc08f7d53>] zpl_writepages+0x103/0x170 [zfs]
[170287.953033]  [<ffffffff8119bf1e>] do_writepages+0x1e/0x30
[170287.953034]  [<ffffffff8118ef86>] __filemap_fdatawrite_range+0xc6/0x100
[170287.953036]  [<ffffffff8118f0ca>] filemap_write_and_wait_range+0x2a/0x70
[170287.953062]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[170287.953065]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[170287.953067]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[170287.953069]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[170287.953177] INFO: task kworker/u16:3:31765 blocked for more than 120 seconds.
[170287.953178]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[170287.953179] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[170287.953179] kworker/u16:3   D ffff880749d47838     0 31765      2 0x00000000
[170287.953183] Workqueue: writeback wb_workfn (flush-zfs-37)
[170287.953184]  ffff880749d47838 ffffffff811ec63a ffff8807faf01b80 ffff88048c348000
[170287.953186]  ffff880749d48000 ffff88081ec96d00 7fffffffffffffff ffff880749d479a8
[170287.953187]  ffffffff8182a610 ffff880749d47850 ffffffff81829e15 0000000000000000
[170287.953189] Call Trace:
[170287.953191]  [<ffffffff811ec63a>] ? kfree+0x13a/0x150
[170287.953193]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[170287.953195]  [<ffffffff81829e15>] schedule+0x35/0x80
[170287.953196]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[170287.953221]  [<ffffffffc088d478>] ? rrm_exit+0x48/0x80 [zfs]
[170287.953224]  [<ffffffff810f597c>] ? ktime_get+0x3c/0xb0
[170287.953226]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[170287.953228]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[170287.953229]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[170287.953231]  [<ffffffff8182a3ae>] __wait_on_bit_lock+0x4e/0xb0
[170287.953233]  [<ffffffff8118d43b>] __lock_page+0xbb/0xe0
[170287.953235]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[170287.953237]  [<ffffffff8119981d>] write_cache_pages+0x2dd/0x510
[170287.953239]  [<ffffffff810ec724>] ? lock_timer_base.isra.22+0x54/0x70
[170287.953265]  [<ffffffffc08f7a20>] ? zpl_write_common_iovec+0xe0/0xe0 [zfs]
[170287.953292]  [<ffffffffc08f7ce4>] zpl_writepages+0x94/0x170 [zfs]
[170287.953294]  [<ffffffff8119bf1e>] do_writepages+0x1e/0x30
[170287.953296]  [<ffffffff8123bbf5>] __writeback_single_inode+0x45/0x330
[170287.953298]  [<ffffffff8123c3f2>] writeback_sb_inodes+0x262/0x600
[170287.953299]  [<ffffffff8123c81c>] __writeback_inodes_wb+0x8c/0xc0
[170287.953301]  [<ffffffff8123cb73>] wb_writeback+0x253/0x310
[170287.953303]  [<ffffffff81229651>] ? get_nr_dirty_inodes+0x51/0x80
[170287.953305]  [<ffffffff8123d3ea>] wb_workfn+0x2ea/0x400
[170287.953307]  [<ffffffff8109a2c5>] process_one_work+0x165/0x480
[170287.953309]  [<ffffffff8109a62b>] worker_thread+0x4b/0x4c0
[170287.953310]  [<ffffffff8109a5e0>] ? process_one_work+0x480/0x480
[170287.953312]  [<ffffffff810a0808>] kthread+0xd8/0xf0
[170287.953313]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
[170287.953315]  [<ffffffff8182e28f>] ret_from_fork+0x3f/0x70
[170287.953316]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
[184208.557065] INFO: task mongod:1917 blocked for more than 120 seconds.
[184208.557068]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[184208.557069] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[184208.557071] mongod          D ffff8805aecefba8     0  1917   5819 0x00000100
[184208.557074]  ffff8805aecefba8 00000000579d9674 ffff8807faf05280 ffff8806d6238000
[184208.557076]  ffff8805aecf0000 ffff88081ed96d00 7fffffffffffffff ffffffff8182a610
[184208.557077]  ffff8805aecefd08 ffff8805aecefbc0 ffffffff81829e15 0000000000000000
[184208.557079] Call Trace:
[184208.557085]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[184208.557087]  [<ffffffff81829e15>] schedule+0x35/0x80
[184208.557089]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[184208.557092]  [<ffffffff8118d939>] ? find_get_pages_tag+0x109/0x190
[184208.557094]  [<ffffffff8182a610>] ? bit_wait+0x60/0x60
[184208.557096]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[184208.557097]  [<ffffffff8182a62b>] bit_wait_io+0x1b/0x70
[184208.557099]  [<ffffffff8182a1bd>] __wait_on_bit+0x5d/0x90
[184208.557101]  [<ffffffff8118d04b>] wait_on_page_bit+0xcb/0xf0
[184208.557104]  [<ffffffff810c3ce0>] ? autoremove_wake_function+0x40/0x40
[184208.557106]  [<ffffffff8118d163>] __filemap_fdatawait_range+0xf3/0x160
[184208.557107]  [<ffffffff8118ef91>] ? __filemap_fdatawrite_range+0xd1/0x100
[184208.557109]  [<ffffffff8118d1e4>] filemap_fdatawait_range+0x14/0x30
[184208.557110]  [<ffffffff8118f0df>] filemap_write_and_wait_range+0x3f/0x70
[184208.557151]  [<ffffffffc08f7ea8>] zpl_fsync+0x38/0x90 [zfs]
[184208.557154]  [<ffffffff8124116b>] vfs_fsync_range+0x4b/0xb0
[184208.557156]  [<ffffffff811cabee>] SyS_msync+0x17e/0x1f0
[184208.557158]  [<ffffffff8182def2>] entry_SYSCALL_64_fastpath+0x16/0x71
[201369.291288] INFO: task txg_sync:4602 blocked for more than 120 seconds.
[201369.291292]       Tainted: P           O    4.4.0-34-generic #53-Ubuntu
[201369.291293] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[201369.291294] txg_sync        D ffff8800d95c3aa8     0  4602      2 0x00000000
[201369.291298]  ffff8800d95c3aa8 ffff88081ed96d00 ffff8807faf05280 ffff8807f627ee00
[201369.291300]  ffff8800d95c4000 ffff88081ed96d00 7fffffffffffffff ffff880485c17988
[201369.291301]  0000000000000001 ffff8800d95c3ac0 ffffffff81829e15 0000000000000000
[201369.291303] Call Trace:
[201369.291309]  [<ffffffff81829e15>] schedule+0x35/0x80
[201369.291311]  [<ffffffff8182cf35>] schedule_timeout+0x1b5/0x270
[201369.291313]  [<ffffffff810ba44c>] ? set_next_entity+0x9c/0xb0
[201369.291316]  [<ffffffff8102d66c>] ? __switch_to+0x1dc/0x5c0
[201369.291318]  [<ffffffff81829344>] io_schedule_timeout+0xa4/0x110
[201369.291325]  [<ffffffffc07b4bec>] cv_wait_common+0xbc/0x140 [spl]
[201369.291327]  [<ffffffff810c3ca0>] ? wake_atomic_t_function+0x60/0x60
[201369.291331]  [<ffffffffc07b4cc8>] __cv_wait_io+0x18/0x20 [spl]
[201369.291369]  [<ffffffffc08f22fe>] zio_wait+0x10e/0x1f0 [zfs]
[201369.291389]  [<ffffffffc087bc58>] dsl_pool_sync+0xb8/0x430 [zfs]
[201369.291411]  [<ffffffffc08975b6>] spa_sync+0x366/0xb30 [zfs]
[201369.291414]  [<ffffffff810ac0c2>] ? default_wake_function+0x12/0x20
[201369.291438]  [<ffffffffc08a8a4a>] txg_sync_thread+0x3ba/0x630 [zfs]
[201369.291461]  [<ffffffffc08a8690>] ? txg_delay+0x180/0x180 [zfs]
[201369.291465]  [<ffffffffc07afe31>] thread_generic_wrapper+0x71/0x80 [spl]
[201369.291469]  [<ffffffffc07afdc0>] ? __thread_exit+0x20/0x20 [spl]
[201369.291470]  [<ffffffff810a0808>] kthread+0xd8/0xf0
[201369.291472]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0
[201369.291474]  [<ffffffff8182e28f>] ret_from_fork+0x3f/0x70
[201369.291475]  [<ffffffff810a0730>] ? kthread_create_on_node+0x1e0/0x1e0