dmesg:
[59449.676839] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[59449.676841] task:CGenericAsyncFi state:D stack: 0 pid:791142 ppid:712731 flags:0x20004000
[59449.676846] Call Trace:
[59449.676849] __schedule+0x44c/0x8a0
[59449.676855] ? __sg_alloc_table+0x6f/0x170
[59449.676859] ? _cond_resched+0x19/0x30
[59449.676862] schedule+0x4f/0xc0
[59449.676863] io_schedule+0x16/0x40
[59449.676867] cv_wait_common+0xae/0x130 [spl]
[59449.676876] ? wait_woken+0x80/0x80
[59449.676880] __cv_wait_io+0x18/0x20 [spl]
[59449.676888] txg_wait_synced_impl+0xd6/0x120 [zfs]
[59449.677004] txg_wait_synced+0x10/0x40 [zfs]
[59449.677101] dmu_tx_wait+0x385/0x390 [zfs]
[59449.677191] ? _cond_resched+0x19/0x30
[59449.677194] dmu_tx_assign+0x16f/0x480 [zfs]
[59449.677279] zfs_write+0x438/0xda0 [zfs]
[59449.677392] zpl_iter_write+0x102/0x160 [zfs]
[59449.677494] new_sync_write+0x117/0x1b0
[59449.677499] vfs_write+0x1ca/0x280
[59449.677502] ksys_write+0x67/0xe0
[59449.677505] __ia32_sys_write+0x18/0x20
[59449.677508] __do_fast_syscall_32+0x65/0xa0
[59449.677511] do_fast_syscall_32+0x34/0x80
[59449.677513] entry_SYSCALL_compat_after_hwframe+0x45/0x4d
[59449.677517] RIP: 0023:0xf7f7e549
[59449.677519] RSP: 002b:00000000aefe9f30 EFLAGS: 00200282 ORIG_RAX: 0000000000000004
[59449.677522] RAX: ffffffffffffffda RBX: 0000000000000088 RCX: 000000009aa5c010