PARTIAL TAKE 909260 - I/O path tracing

[Nathan Scott <nathans@xxxxxxxxxxxxxxxxxxxxxxx>]

Add I/O path tracing code, 'twas useful in diagnosing that
last unwritten extent problem and may be useful in other
contexts as well.


Date:  Mon Feb  9 21:51:00 PST 2004
Workarea:  snort.melbourne.sgi.com:/home/nathans/xfs-linux

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/xfs-kern/xfs-linux


Modid:  xfs-linux:xfs-kern:166497a
xfsidbg.c - 1.253
xfs_iomap.c - 1.23
linux-2.6/xfs_lrw.h - 1.42
linux-2.6/xfs_lrw.c - 1.203
linux-2.6/xfs_aops.c - 1.62
linux-2.4/xfs_lrw.h - 1.42
linux-2.4/xfs_lrw.c - 1.212
linux-2.4/xfs_aops.c - 1.70