[  468.667585] ======================================================
[  468.669774] [ INFO: possible circular locking dependency detected ]
[  468.669983] 4.0.0-rc5-196355-gd50b8fe-dirty #19 Not tainted
[  468.669983] -------------------------------------------------------
[  468.669983] splice-fcntl/2950 is trying to acquire lock:
[  468.669983]  (&sb->s_type->i_mutex_key#11){+.+.+.}, at: [<ffffffff812c3f60>] xfs_rw_ilock+0x21/0x31
[  468.669983]
but task is already holding lock:
[  468.669983]  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff8118f93e>] pipe_lock+0x1c/0x1e
[  468.669983]
which lock already depends on the new lock.

[  468.669983]
the existing dependency chain (in reverse order) is:
[  468.669983]
-> #2 (&pipe->mutex/1){+.+.+.}:
[  468.669983]        [<ffffffff810c4f5c>] lock_acquire+0xd7/0x112
[  468.669983]        [<ffffffff816f1f88>] mutex_lock_nested+0x63/0x5ab
[  468.669983]        [<ffffffff8118f93e>] pipe_lock+0x1c/0x1e
[  468.669983]        [<ffffffff811aff79>] splice_to_pipe+0x2d/0x203
[  468.669983]        [<ffffffff811b0f82>] __generic_file_splice_read+0x41f/0x440
[  468.669983]        [<ffffffff811b0fec>] generic_file_splice_read+0x49/0x73
[  468.669983]        [<ffffffff812c50ac>] xfs_file_splice_read+0xfb/0x144
[  468.669983]        [<ffffffff811af6a4>] do_splice_to+0x74/0x81
[  468.669983]        [<ffffffff811b0751>] SyS_splice+0x4b6/0x55e
[  468.669983]        [<ffffffff816f5f09>] system_call_fastpath+0x12/0x17
[  468.669983]
-> #1 (&(&ip->i_iolock)->mr_lock){++++++}:
[  468.669983]        [<ffffffff810c4f5c>] lock_acquire+0xd7/0x112
[  468.669983]        [<ffffffff810bf5d0>] down_write_nested+0x4b/0xad
[  468.669983]        [<ffffffff812d1c5f>] xfs_ilock+0xdb/0x14b
[  468.669983]        [<ffffffff812c3f6b>] xfs_rw_ilock+0x2c/0x31
[  468.669983]        [<ffffffff812c561e>] xfs_file_buffered_aio_write+0x59/0x1e8
[  468.669983]        [<ffffffff812c5830>] xfs_file_write_iter+0x83/0x107
[  468.669983]        [<ffffffff811882e7>] new_sync_write+0x64/0x82
[  468.669983]        [<ffffffff8118956b>] vfs_write+0xb5/0x14d
[  468.669983]        [<ffffffff811896eb>] SyS_write+0x5c/0x8c
[  468.669983]        [<ffffffff816f5f09>] system_call_fastpath+0x12/0x17
[  468.669983]
-> #0 (&sb->s_type->i_mutex_key#11){+.+.+.}:
[  468.669983]        [<ffffffff810c4b60>] __lock_acquire+0xbd6/0xefb
[  468.669983]        [<ffffffff810c4f5c>] lock_acquire+0xd7/0x112
[  468.669983]        [<ffffffff816f1f88>] mutex_lock_nested+0x63/0x5ab
[  468.669983]        [<ffffffff812c3f60>] xfs_rw_ilock+0x21/0x31
[  468.669983]        [<ffffffff812c561e>] xfs_file_buffered_aio_write+0x59/0x1e8
[  468.669983]        [<ffffffff812c5830>] xfs_file_write_iter+0x83/0x107
[  468.669983]        [<ffffffff81187e4c>] vfs_iter_write+0x4c/0x6b
[  468.669983]        [<ffffffff811afdfb>] iter_file_splice_write+0x230/0x33a
[  468.669983]        [<ffffffff811b06a4>] SyS_splice+0x409/0x55e
[  468.669983]        [<ffffffff816f5f09>] system_call_fastpath+0x12/0x17
[  468.669983]
other info that might help us debug this[  604.889687] serial8250: too much work for irq4
:

[  468.669983] Chain exists of:
  &sb->s_type->i_mutex_key#11 --> &(&ip->i_iolock)->mr_lock --> &pipe->mutex/1

[  468.669983]  Possible unsafe locking scenario:

[  468.669983]        CPU0                    CPU1
[  468.669983]        ----                    ----
[  468.669983]   lock(&pipe->mutex/1);
[  468.669983]                                lock(&(&ip->i_iolock)->mr_lock);
[  468.669983]                                lock(&pipe->mutex/1);
[  468.669983]   lock(&sb->s_type->i_mutex_key#11);
[  468.669983]
 *** DEADLOCK ***

[  468.669983] 2 locks held by splice-fcntl/2950:
[  468.669983]  #0:  (sb_writers#9){.+.+.+}, at: [<ffffffff811b0671>] SyS_splice+0x3d6/0x55e
[  468.669983]  #1:  (&pipe->mutex/1){+.+.+.}, at: [<ffffffff8118f93e>] pipe_lock+0x1c/0x1e
[  468.669983]
stack backtrace:
[  468.669983] CPU: 1 PID: 2950 Comm: splice-fcntl Not tainted 4.0.0-rc5-196355-gd50b8fe-dirty #19
[  468.669983] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
[  468.669983]  ffffffff8247a700 ffff88006b03fa18 ffffffff816eff65 0000000000000001
[  468.669983]  ffffffff824924b0 ffff88006b03fa68 ffffffff810c2fae ffff88006b03fa68
[  468.669983]  ffffffff822781f0 ffff88007c062de0 ffff88007c0624b0 ffff88007c062de0
[  468.669983] Call Trace:
[  468.669983]  [<ffffffff816eff65>] dump_stack+0x48/0x5b
[  468.669983]  [<ffffffff810c2fae>] print_circular_bug+0x1f8/0x209
[  468.669983]  [<ffffffff810c4b60>] __lock_acquire+0xbd6/0xefb
[  468.669983]  [<ffffffff812c3f60>] ? xfs_rw_ilock+0x21/0x31
[  468.669983]  [<ffffffff810c4f5c>] lock_acquire+0xd7/0x112
[  468.669983]  [<ffffffff812c3f60>] ? xfs_rw_ilock+0x21/0x31
[  468.669983]  [<ffffffff816f1f88>] mutex_lock_nested+0x63/0x5ab
[  468.669983]  [<ffffffff812c3f60>] ? xfs_rw_ilock+0x21/0x31
[  468.669983]  [<ffffffff812c3f60>] ? xfs_rw_ilock+0x21/0x31
[  468.669983]  [<ffffffff810c3909>] ? mark_held_locks+0x59/0x77
[  468.669983]  [<ffffffff81183919>] ? slab_free_hook+0x7a/0x9a
[  468.669983]  [<ffffffff8107b40b>] ? kvm_clock_read+0x1e/0x20
[  468.669983]  [<ffffffff812c3f60>] xfs_rw_ilock+0x21/0x31
[  468.669983]  [<ffffffff812c561e>] xfs_file_buffered_aio_write+0x59/0x1e8
[  468.669983]  [<ffffffff810c3c63>] ? trace_hardirqs_on_caller+0x164/0x19b
[  468.669983]  [<ffffffff810c3ca7>] ? trace_hardirqs_on+0xd/0xf
[  468.669983]  [<ffffffff8118f93e>] ? pipe_lock+0x1c/0x1e
[  468.669983]  [<ffffffff812c5830>] xfs_file_write_iter+0x83/0x107
[  468.669983]  [<ffffffff81187e4c>] vfs_iter_write+0x4c/0x6b
[  468.669983]  [<ffffffff811afdfb>] iter_file_splice_write+0x230/0x33a
[  468.669983]  [<ffffffff811b06a4>] SyS_splice+0x409/0x55e
[  468.669983]  [<ffffffff811a1167>] ? __fd_install+0x9f/0xab
[  468.669983]  [<ffffffff810c3c63>] ? trace_hardirqs_on_caller+0x164/0x19b
[  468.669983]  [<ffffffff816f5f09>] system_call_fastpath+0x12/0x17