Comment 11 for bug 1315955

Same problem for me
Ubuntu version: Ubuntu 14.04.2 LTS
Kernel version: 3.13.0-53-generic #89-Ubuntu SMP Wed May 20 10:34:39 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

Jun 8 17:28:41 server1 kernel: [ 1561.791349] INFO: task nfsd:1986 blocked for more than 120 seconds.
Jun 8 17:28:41 server1 kernel: [ 1561.791366] Tainted: P OX 3.13.0-53-generic #89-Ubuntu
Jun 8 17:28:41 server1 kernel: [ 1561.791384] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Jun 8 17:28:41 server1 kernel: [ 1561.791405] nfsd D ffff88041fb93180 0 1986 2 0x00000000
Jun 8 17:28:41 server1 kernel: [ 1561.791407] ffff8803f94d18a0 0000000000000046 ffff8800d4588000 ffff8803f94d1fd8
Jun 8 17:28:41 server1 kernel: [ 1561.791409] 0000000000013180 0000000000013180 ffff8800d4588000 ffff880256c1e8f8
Jun 8 17:28:41 server1 kernel: [ 1561.791410] ffff880256c1e8a8 ffff880256c1e900 ffff880256c1e8d0 0000000000000000
Jun 8 17:28:41 server1 kernel: [ 1561.791412] Call Trace:
Jun 8 17:28:41 server1 kernel: [ 1561.791414] [<ffffffff81727229>] schedule+0x29/0x70
Jun 8 17:28:41 server1 kernel: [ 1561.791419] [<ffffffffa007eaf5>] cv_wait_common+0xe5/0x120 [spl]
Jun 8 17:28:41 server1 kernel: [ 1561.791421] [<ffffffff810ab220>] ? prepare_to_wait_event+0x100/0x100
Jun 8 17:28:41 server1 kernel: [ 1561.791426] [<ffffffffa007eb45>] __cv_wait+0x15/0x20 [spl]
Jun 8 17:28:41 server1 kernel: [ 1561.791437] [<ffffffffa0139da3>] dmu_buf_hold_array_by_dnode+0x233/0x570 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791449] [<ffffffffa013a1bd>] dmu_buf_hold_array+0x5d/0x80 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791461] [<ffffffffa013ba01>] dmu_read_uio+0x41/0xe0 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791480] [<ffffffffa01bafbc>] zfs_read+0x14c/0x450 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791492] [<ffffffffa01385fe>] ? dmu_object_size_from_db+0x5e/0x80 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791511] [<ffffffffa01d757a>] zpl_aio_read+0xda/0x130 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791513] [<ffffffff811bd9cc>] do_sync_readv_writev+0x4c/0x80
Jun 8 17:28:41 server1 kernel: [ 1561.791515] [<ffffffff811bee90>] do_readv_writev+0xb0/0x220
Jun 8 17:28:41 server1 kernel: [ 1561.791534] [<ffffffffa01bac57>] ? zfs_open+0x87/0x120 [zfs]
Jun 8 17:28:41 server1 kernel: [ 1561.791536] [<ffffffff813213d3>] ? ima_get_action+0x23/0x30
Jun 8 17:28:41 server1 kernel: [ 1561.791538] [<ffffffff813206b2>] ? process_measurement+0x82/0x2c0
Jun 8 17:28:41 server1 kernel: [ 1561.791539] [<ffffffff811bf02d>] vfs_readv+0x2d/0x50
Jun 8 17:28:41 server1 kernel: [ 1561.791543] [<ffffffffa0401aae>] nfsd_vfs_read.isra.12+0x6e/0x160 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791547] [<ffffffffa0402da9>] ? nfsd_open+0xb9/0x190 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791551] [<ffffffffa0403076>] nfsd_read+0x1e6/0x2c0 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791557] [<ffffffffa040ce4c>] nfsd3_proc_read+0xcc/0x170 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791561] [<ffffffffa03fdd3b>] nfsd_dispatch+0xbb/0x200 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791568] [<ffffffffa036262d>] svc_process_common+0x46d/0x6d0 [sunrpc]
Jun 8 17:28:41 server1 kernel: [ 1561.791575] [<ffffffffa0362997>] svc_process+0x107/0x170 [sunrpc]
Jun 8 17:28:41 server1 kernel: [ 1561.791578] [<ffffffffa03fd71f>] nfsd+0xbf/0x130 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791582] [<ffffffffa03fd660>] ? nfsd_destroy+0x80/0x80 [nfsd]
Jun 8 17:28:41 server1 kernel: [ 1561.791583] [<ffffffff8108b6b2>] kthread+0xd2/0xf0
Jun 8 17:28:41 server1 kernel: [ 1561.791585] [<ffffffff8108b5e0>] ? kthread_create_on_node+0x1c0/0x1c0
Jun 8 17:28:41 server1 kernel: [ 1561.791586] [<ffffffff81733868>] ret_from_fork+0x58/0x90
Jun 8 17:28:41 server1 kernel: [ 1561.791587] [<ffffffff8108b5e0>] ? kthread_create_on_node+0x1c0/0x1c0