xfs: fold perag loop iteration logic into helper function

xfs: fold perag loop iteration logic into helper function

[ Upstream commit bf2307b195135ed9c95eebb38920d8bd41843092 ]

Fold the loop iteration logic into a helper in preparation for
further fixups. No functional change in this patch.

[backport: dependency for f1788b5e5ee25bedf00bb4d25f82b93820d61189]

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Acked-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>