xen/p2m: Move code around to allow for better re-usage.

We are going to be using the early_alloc_p2m (and
early_alloc_p2m_middle) code in follow up patches which
are not related to setting identity pages.

Hence lets move the code out in its own function and
rename them as appropiate.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

arch/x86/xen/p2m.c

@@ -499,7 +499,7 @@ static bool alloc_p2m(unsigned long pfn)
 	return true;
 }
 
-static bool __init __early_alloc_p2m(unsigned long pfn)
+static bool __init early_alloc_p2m_middle(unsigned long pfn)
 {
 	unsigned topidx, mididx, idx;
 
@@ -541,24 +541,9 @@ static bool __init __early_alloc_p2m(unsigned long pfn)
 	}
 	return idx != 0;
 }
-unsigned long __init set_phys_range_identity(unsigned long pfn_s,
-				      unsigned long pfn_e)
-{
-	unsigned long pfn;
-
-	if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
-		return 0;
-
-	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
-		return pfn_e - pfn_s;
 
-	if (pfn_s > pfn_e)
-		return 0;
-
-	for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
-		pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
-		pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
-	{
+static bool __init early_alloc_p2m(unsigned long pfn)
+{
 	unsigned topidx = p2m_top_index(pfn);
 	unsigned long *mid_mfn_p;
 	unsigned long **mid;
@@ -582,12 +567,33 @@ unsigned long __init set_phys_range_identity(unsigned long pfn_s,
 		p2m_top_mfn_p[topidx] = mid_mfn_p;
 		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);
 		/* Note: we don't set mid_mfn_p[midix] here,
-		 	 * look in __early_alloc_p2m */
+		 * look in early_alloc_p2m_middle */
 	}
+	return true;
+}
+unsigned long __init set_phys_range_identity(unsigned long pfn_s,
+				      unsigned long pfn_e)
+{
+	unsigned long pfn;
+
+	if (unlikely(pfn_s >= MAX_P2M_PFN || pfn_e >= MAX_P2M_PFN))
+		return 0;
+
+	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
+		return pfn_e - pfn_s;
+
+	if (pfn_s > pfn_e)
+		return 0;
+
+	for (pfn = (pfn_s & ~(P2M_MID_PER_PAGE * P2M_PER_PAGE - 1));
+		pfn < ALIGN(pfn_e, (P2M_MID_PER_PAGE * P2M_PER_PAGE));
+		pfn += P2M_MID_PER_PAGE * P2M_PER_PAGE)
+	{
+		WARN_ON(!early_alloc_p2m(pfn));
 	}
 
-	__early_alloc_p2m(pfn_s);
-	__early_alloc_p2m(pfn_e);
+	early_alloc_p2m_middle(pfn_s);
+	early_alloc_p2m_middle(pfn_e);
 
 	for (pfn = pfn_s; pfn < pfn_e; pfn++)
 		if (!__set_phys_to_machine(pfn, IDENTITY_FRAME(pfn)))