TAKE - performance work for O_SYNC writes

[Steve Lord <lord@sgi.com>]

for synchronous transactions, allow the in core log buffer to wait
around in active state for as long as possible. This allows us to
coalesce several transactions into one buffer and reduce the disk
traffic.


Date:  Mon Dec  2 10:26:49 PST 2002
Workarea:  jen.americas.sgi.com:/src/lord/xfs-linux.2.4

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.4.x-xfs


Modid:  2.4.x-xfs:slinx:134077a
linux/fs/xfs/xfs_log.c - 1.262
	- Introduce a new sync variable in the iclog structure to sync
	  between the last log write and the next one in the case of
	  sync transactions forcing iclogs out to disk early.

linux/fs/xfs/xfs_log_priv.h - 1.85
	- new sync variable in the iclog structure