[PATCH v7 5/8] x86/e820: Refactor e820__range_remove

[Martin Fernandez <martin.fernandez@eclypsium.com>]

Refactor e820__range_remove with the introduction of
e820_remover_data, indented to be used as the void pointer in the
e820_entry_updater callbacks, and the implementation of the callbacks
remove a range in the e820_table.

Signed-off-by: Martin Fernandez <martin.fernandez@eclypsium.com>
---
 arch/x86/kernel/e820.c | 112 ++++++++++++++++++++++-------------------
 1 file changed, 60 insertions(+), 52 deletions(-)

diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 763b8b20a1fd..9e32c9819e99 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -717,66 +717,74 @@ static u64 __init e820__range_update_kexec(u64 start, u64 size,
 	return __e820__range_update(e820_table_kexec, start, size, old_type, new_type);
 }
 
-/* Remove a range of memory from the E820 table: */
-u64 __init e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type)
-{
-	int i;
-	u64 end;
-	u64 real_removed_size = 0;
-
-	if (size > (ULLONG_MAX - start))
-		size = ULLONG_MAX - start;
-
-	end = start + size;
-	printk(KERN_DEBUG "e820: remove [mem %#010Lx-%#010Lx] ", start, end - 1);
-	if (check_type)
-		e820_print_type(old_type);
-	pr_cont("\n");
-
-	for (i = 0; i < e820_table->nr_entries; i++) {
-		struct e820_entry *entry = &e820_table->entries[i];
-		u64 final_start, final_end;
-		u64 entry_end;
+/**
+ * struct e820_remover_data - Helper type for e820__range_remove().
+ * @old_type: old_type parameter of e820__range_remove().
+ * @check_type: check_type parameter of e820__range_remove().
+ *
+ * This is intended to be used as the @data argument for the
+ * e820_entry_updater callbacks.
+ */
+struct e820_remover_data {
+	enum e820_type old_type;
+	bool check_type;
+};
 
-		if (check_type && entry->type != old_type)
-			continue;
+static bool __init remover__should_update(const struct e820_entry *entry,
+					  const void *data)
+{
+	const struct e820_remover_data *remover_data =
+		(const struct e820_remover_data *)data;
 
-		entry_end = entry->addr + entry->size;
+	return !remover_data->check_type ||
+	       entry->type == remover_data->old_type;
+}
 
-		/* Completely covered? */
-		if (entry->addr >= start && entry_end <= end) {
-			real_removed_size += entry->size;
-			memset(entry, 0, sizeof(*entry));
-			continue;
-		}
+static void __init remover__update(struct e820_entry *entry, const void *data)
+{
+	memset(entry, 0, sizeof(*entry));
+}
 
-		/* Is the new range completely covered? */
-		if (entry->addr < start && entry_end > end) {
-			e820__range_add(end, entry_end - end, entry->type);
-			entry->size = start - entry->addr;
-			real_removed_size += size;
-			continue;
-		}
+static void __init remover__new(struct e820_table *table, u64 new_start,
+				u64 new_size, const struct e820_entry *original,
+				const void *data)
+{
+}
 
-		/* Partially covered: */
-		final_start = max(start, entry->addr);
-		final_end = min(end, entry_end);
-		if (final_start >= final_end)
-			continue;
+/**
+ * e820__range_remove() - Remove an address range from e820_table.
+ * @start: Start of the address range.
+ * @size: Size of the address range.
+ * @old_type: Type of the entries that we want to remove.
+ * @check_type: Bool to decide if ignore @old_type or not.
+ *
+ * Remove [@start, @start + @size) from e820_table. If @check_type is
+ * true remove only entries with type @old_type.
+ *
+ * Return: The size removed.
+ */
+u64 __init e820__range_remove(u64 start, u64 size, enum e820_type old_type,
+			      bool check_type)
+{
+	struct e820_entry_updater updater = {
+		.should_update = remover__should_update,
+		.update = remover__update,
+		.new = remover__new
+	};
 
-		real_removed_size += final_end - final_start;
+	struct e820_remover_data data = {
+		.check_type = check_type,
+		.old_type = old_type
+	};
 
-		/*
-		 * Left range could be head or tail, so need to update
-		 * the size first:
-		 */
-		entry->size -= final_end - final_start;
-		if (entry->addr < final_start)
-			continue;
+	printk(KERN_DEBUG "e820: remove [mem %#018Lx-%#018Lx] ", start,
+	       start + size - 1);
+	if (check_type)
+		e820_print_type(old_type);
+	pr_cont("\n");
 
-		entry->addr = final_end;
-	}
-	return real_removed_size;
+	return __e820__handle_range_update(e820_table, start, size, &updater,
+					    &data);
 }
 
 void __init e820__update_table_print(void)
-- 
2.30.2