xfs: factor rmap btree size into the indlen calculations

xfs: factor rmap btree size into the indlen calculations

commit fd26a88093bab6529ea2de819114ca92dbd1d71d upstream.

When we're estimating the amount of space it's going to take to satisfy
a delalloc reservation, we need to include the space that we might need
to grow the rmapbt.  This helps us to avoid running out of space later
when _iomap_write_allocate needs more space than we reserved.  Eryu Guan
observed this happening on generic/224 when sunit/swidth were set.

Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>