[V4]fix ocfs2 aio/dio writing process hang

[Junxiao Bi]

V4 changes:
add Acked-by: Joel Becker <jlbec@xxxxxxxxxxxx>

V3 changes:
- add Cc: stable@xxxxxxxxxxxxxxx in the patch header to align with stable rules
- add Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx>

V2 changes:
- update the patch header of the first patch to make it more clear.


This patch list fixes an issue about ocfs2 aio/dio write process hang.
The call trace is like this:
@  cat /proc/15913/stack
@ [<ffffffffa06e1085>] ocfs2_aiodio_wait+0x85/0xc0 [ocfs2]
@ [<ffffffffa06e3e39>] ocfs2_file_aio_write+0x99/0xa0 [ocfs2]
@ [<ffffffff811ace97>] aio_rw_vect_retry+0x87/0x150
@ [<ffffffff811aebd1>] aio_run_iocb+0x71/0x170
@ [<ffffffff811af59b>] io_submit_one+0x1ab/0x280
@ [<ffffffff811af77c>] do_io_submit+0x10c/0x1c0
@ [<ffffffff811af840>] sys_io_submit+0x10/0x20
@ [<ffffffff81509b42>] system_call_fastpath+0x16/0x1b
@ [<ffffffffffffffff>] 0xffffffffffffffff
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