powerpc/mm: Clean up memory hotplug failure paths

This makes a number of cleanups to handling of mapping failures during
memory hotplug on Power:

For errors creating the linear mapping for the hot-added region:
* This is now reported with EFAULT which is more appropriate than the
previous EINVAL (the failure is unlikely to be related to the
function's parameters)
* An error in this path now prints a warning message, rather than just
silently failing to add the extra memory.
* Previously a failure here could result in the region being partially
mapped. We now clean up any partial mapping before failing.

For errors creating the vmemmap for the hot-added region:
* This is now reported with EFAULT instead of causing a BUG() - this
could happen for external reason (e.g. full hash table) so it's better
to handle this non-fatally
* An error message is also printed, so the failure won't be silent
* As above a failure could cause a partially mapped region, we now
clean this up. [mpe: move htab_remove_mapping() out of #ifdef
CONFIG_MEMORY_HOTPLUG to enable this]

Signed-off-by: David Gibson <[e-mail]>
Reviewed-by: Paul Mackerras <[e-mail]>
Reviewed-by: Aneesh Kumar K.V <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>

arch/powerpc/mm/hash_utils_64.c

···
 	return ret < 0 ? ret : 0;
 }
 
-#ifdef CONFIG_MEMORY_HOTPLUG
 int htab_remove_mapping(unsigned long vstart, unsigned long vend,
 		      int psize, int ssize)
 {
···
 
 	return ret;
 }
-#endif /* CONFIG_MEMORY_HOTPLUG */
 
 static int __init htab_dt_scan_seg_sizes(unsigned long node,
 					 const char *uname, int depth,
···
 #ifdef CONFIG_MEMORY_HOTPLUG
 int create_section_mapping(unsigned long start, unsigned long end)
 {
-	return htab_bolt_mapping(start, end, __pa(start),
-				 pgprot_val(PAGE_KERNEL), mmu_linear_psize,
-				 mmu_kernel_ssize);
+	int rc = htab_bolt_mapping(start, end, __pa(start),
+				   pgprot_val(PAGE_KERNEL), mmu_linear_psize,
+				   mmu_kernel_ssize);
+
+	if (rc < 0) {
+		int rc2 = htab_remove_mapping(start, end, mmu_linear_psize,
+					      mmu_kernel_ssize);
+		BUG_ON(rc2 && (rc2 != -ENOENT));
+	}
+	return rc;
 }
 
 int remove_section_mapping(unsigned long start, unsigned long end)

arch/powerpc/mm/init_64.c

···
  */
 
 #ifdef CONFIG_PPC_BOOK3E
-static void __meminit vmemmap_create_mapping(unsigned long start,
-					     unsigned long page_size,
-					     unsigned long phys)
+static int __meminit vmemmap_create_mapping(unsigned long start,
+					    unsigned long page_size,
+					    unsigned long phys)
 {
 	/* Create a PTE encoding without page size */
 	unsigned long i, flags = _PAGE_PRESENT | _PAGE_ACCESSED |
···
 	 */
 	for (i = 0; i < page_size; i += PAGE_SIZE)
 		BUG_ON(map_kernel_page(start + i, phys, flags));
+
+	return 0;
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
···
 }
 #endif
 #else /* CONFIG_PPC_BOOK3E */
-static void __meminit vmemmap_create_mapping(unsigned long start,
-					     unsigned long page_size,
-					     unsigned long phys)
+static int __meminit vmemmap_create_mapping(unsigned long start,
+					    unsigned long page_size,
+					    unsigned long phys)
 {
-	int  mapped = htab_bolt_mapping(start, start + page_size, phys,
-					pgprot_val(PAGE_KERNEL),
-					mmu_vmemmap_psize,
-					mmu_kernel_ssize);
-	BUG_ON(mapped < 0);
+	int rc = htab_bolt_mapping(start, start + page_size, phys,
+				   pgprot_val(PAGE_KERNEL),
+				   mmu_vmemmap_psize, mmu_kernel_ssize);
+	if (rc < 0) {
+		int rc2 = htab_remove_mapping(start, start + page_size,
+					      mmu_vmemmap_psize,
+					      mmu_kernel_ssize);
+		BUG_ON(rc2 && (rc2 != -ENOENT));
+	}
+	return rc;
 }
 
 #ifdef CONFIG_MEMORY_HOTPLUG
···
 
 	for (; start < end; start += page_size) {
 		void *p;
+		int rc;
 
 		if (vmemmap_populated(start, page_size))
 			continue;
···
 		pr_debug("      * %016lx..%016lx allocated at %p\n",
 			 start, start + page_size, p);
 
-		vmemmap_create_mapping(start, page_size, __pa(p));
+		rc = vmemmap_create_mapping(start, page_size, __pa(p));
+		if (rc < 0) {
+			pr_warning(
+				"vmemmap_populate: Unable to create vmemmap mapping: %d\n",
+				rc);
+			return -EFAULT;
+		}
 	}
 
 	return 0;

arch/powerpc/mm/mem.c

···
 	struct zone *zone;
 	unsigned long start_pfn = start >> PAGE_SHIFT;
 	unsigned long nr_pages = size >> PAGE_SHIFT;
+	int rc;
 
 	pgdata = NODE_DATA(nid);
 
 	start = (unsigned long)__va(start);
-	if (create_section_mapping(start, start + size))
-		return -EINVAL;
+	rc = create_section_mapping(start, start + size);
+	if (rc) {
+		pr_warning(
+			"Unable to create mapping for hot added memory 0x%llx..0x%llx: %d\n",
+			start, start + size, rc);
+		return -EFAULT;
+	}
 
 	/* this should work for most non-highmem platforms */
 	zone = pgdata->node_zones +