[PATCH 00/27] xfs_bmapi split and cleanups V2

[Christoph Hellwig]

This series, which is largely based on one that Dave published a couple month
ago, splits up the many armed hyrda called xfs_bmapi into multiple smaller
functions, and reduced stack usage in those pathes.

The main visible change to the rest of xfs is that there are three new
interfaces that replace xfs_bmapi:  xfs_bmapi_read to read extent maps,
xfs_bmapi_delay to add new unwritten extents, and xfs_bmapi to allocate
or convert real and unwrittent extents.

changes from V1:
 - address various review comments from Alex
 - make sure all attributions are correct
 - add another patch from Dave's original series, which was lost before