(12:05:55 PM) sage@newdream.net: [6]kdb> bt
Stack traceback for pid 16056
0xffff88020d26deb0    16056    14349  1    6   R  0xffff88020d26e330 *ffsb
 ffff88020c4a9988 0000000000000018 0000000000000000 ffffea0005b973c0
 000010001ec93e08 00000000017e0000 0000000000001000 00000000017df000
 ffff880223335f40 ffffea0005b973c0 ffff88021ec93e08 ffff88020c4a9a18
Call Trace:
 [<ffffffff81130d45>] ? grab_cache_page_write_begin+0x95/0xf0
 [<ffffffffa060fbe5>] ? ceph_write_begin+0xe5/0x210 [ceph]
 [<ffffffff8113062a>] ? generic_file_buffered_write+0x11a/0x290
 [<ffffffff81131dd6>] ? __generic_file_aio_write+0x1b6/0x3b0
 [<ffffffff81132033>] ? generic_file_aio_write+0x63/0x100
 [<ffffffff81132051>] ? generic_file_aio_write+0x81/0x100
 [<ffffffffa060be31>] ? ceph_aio_write+0x741/0xac0 [ceph]
 [<ffffffff810b4d72>] ? __lock_acquire+0x302/0x1d10
 [<ffffffff81183813>] ? do_sync_write+0xa3/0xe0
 [<ffffffff81183ec3>] ? vfs_write+0xb3/0x180
 [<ffffffff81184202>] ? sys_write+0x52/0xa0
 [<ffffffff81666619>] ? system_call_fastpath+0x16/0x1b

(12:06:00 PM) sage@newdream.net: several machines hung this way
(12:06:08 PM) sage@newdream.net: something seems broken on kclient testing branch