iomap: Add DIO tracepoints

Add trace_iomap_dio_rw_begin, trace_iomap_dio_rw_queued and
trace_iomap_dio_complete tracepoint.
trace_iomap_dio_rw_queued is mostly only to know that the request was
queued and -EIOCBQUEUED was returned. It is mostly trace_iomap_dio_rw_begin
& trace_iomap_dio_complete which has all the details.

<example output log>
a.out-2073 [006] 134.225717: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x0 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT|WRITE dio_flags DIO_FORCE_WAIT aio 1
a.out-2073 [006] 134.226234: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT|WRITE aio 1 error 0 ret 4096
a.out-2074 [006] 136.225975: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x1000 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT dio_flags aio 1
a.out-2074 [006] 136.226173: iomap_dio_rw_queued: dev 7:7 ino 0xe size 0x1000 offset 0x1000 length 0x0
ksoftirqd/3-31 [003] 136.226389: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT aio 1 error 0 ret 4096
a.out-2075 [003] 141.674969: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x1000 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT|WRITE dio_flags aio 1
a.out-2075 [003] 141.676085: iomap_dio_rw_queued: dev 7:7 ino 0xe size 0x1000 offset 0x1000 length 0x0
kworker/2:0-27 [002] 141.676432: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT|WRITE aio 1 error 0 ret 4096
a.out-2077 [006] 143.443746: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x1000 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT dio_flags aio 1
a.out-2077 [006] 143.443866: iomap_dio_rw_queued: dev 7:7 ino 0xe size 0x1000 offset 0x1000 length 0x0
ksoftirqd/5-41 [005] 143.444134: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT aio 1 error 0 ret 4096
a.out-2078 [007] 146.716833: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x1000 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT dio_flags aio 0
a.out-2078 [007] 146.717639: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT aio 0 error 0 ret 4096
a.out-2079 [006] 148.972605: iomap_dio_rw_begin: dev 7:7 ino 0xe size 0x1000 offset 0x0 length 0x1000 done_before 0x0 flags DIRECT dio_flags aio 0
a.out-2079 [006] 148.973099: iomap_dio_complete: dev 7:7 ino 0xe size 0x1000 offset 0x1000 flags DIRECT aio 0 error 0 ret 4096

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
[djwong: line up strings all prettylike]
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

iomap: lift common tracing code from xfs to iomap

Lift the xfs code for tracing address space operations to the iomap
layer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>