TAKE - do not submit I/O to devices which cannot take it

[Steve Lord <lord@xxxxxxx>]

Fix a couple of pagebuf end cases, in particular, deal with block
device which is not correctly initialized and do not submit a bio
to it - that trips a BUG.


Date:  Tue Jul 29 09:56:00 PDT 2003
Workarea:  jen.americas.sgi.com:/src/lord/xfs-linux.2.5

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.5.x-xfs


Modid:  2.5.x-xfs:slinx:154483a
linux/fs/xfs/pagebuf/page_buf.c - 1.115
        - Deal with the case where a block device will not take any I/O,
          do not submit empty bio structures to it.

linux/fs/xfs/linux/xfs_aops.c - 1.44
        - Fix sign of error variable