Merge tag 'reflink-speedups-5.19_2022-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-5.19-for-next

xfs: fix reflink inefficiencies

As Dave Chinner has complained about on IRC, there are a couple of
things about reflink that are very inefficient.  First of all, we
limited the size of all bunmapi operations to avoid flooding the log
with defer ops in the worst case, but recent changes to the defer
ops code have solved that problem, so get rid of the bunmapi length
clamp.

Second, the log reservations for reflink operations are far far
larger than they need to be.  Shrink them to exactly what we need to
handle each deferred RUI and CUI log item, and no more.  Also reduce
logcount because we don't need 8 rolls per operation.  Introduce a
transaction reservation compatibility layer to avoid changing the
minimum log size calculations.
Signed-off-by: Dave Chinner <david@fromorbit.com>