TAKE - fix an enospc race

[Nathan Scott <nathans@xxxxxxxxxxxxxxxxxxxxxxx>]

Fix an infinite writepage loop under a combination of low free
space, and racing write/unlink calls to the same file.

Date:  Thu Nov 13 14:22:14 PST 2003
Workarea:  snort.melbourne.sgi.com:/home/nathans/us-kern-2.4.x-xfs
Author:  nathans
Merged by:  nathans
Merged mods:  xfs-linux:slinx:161773a

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


Modid:  2.4.x-xfs-kern:slinx:161773a
linux/xfs_aops.c - 1.21
        - Merge of xfs-linux:slinx:161773a by nathans.