Two of the callers to xfs_alloc_vextent_this_ag() actually want
exact block number allocation, not anywhere-in-ag allocation. Split
this out from _this_ag() as a first class citizen so no external
extent allocation code needs to care about args->type anymore.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NDarrick J. Wong <djwong@kernel.org>