[MINI-OS PATCH 05/19] mm: refactor init_page_allocator()

[Juergen Gross <jgross@xxxxxxxx>]

Split init_page_allocator() into three functions in order to prepare
for sparing some memory from being added to the buddy allocator.

Use a function pointer for selecting the function used for handling a
memory range, as this will be needed by a future patch. For the same
reason make iterate_memory_range() globally visible.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 include/mm.h |   3 ++
 mm.c         | 111 +++++++++++++++++++++++++++++----------------------
 2 files changed, 66 insertions(+), 48 deletions(-)

diff --git a/include/mm.h b/include/mm.h
index 0a16d56c..1dc89ddb 100644
--- a/include/mm.h
+++ b/include/mm.h
@@ -95,4 +95,7 @@ void fini_mm(void);
 
 void change_readonly(bool readonly);
 
+void iterate_memory_range(unsigned long min, unsigned long max,
+                          void (*func)(unsigned long, unsigned long));
+
 #endif /* _MM_H_ */
diff --git a/mm.c b/mm.c
index 9236db58..858dc108 100644
--- a/mm.c
+++ b/mm.c
@@ -150,16 +150,74 @@ static void dequeue_elem(chunk_head_t *elem)
     elem->next->prev = elem->prev;
 }
 
+static void add_memory_range(unsigned long r_min, unsigned long r_max)
+{
+    unsigned int i;
+    unsigned long range;
+    chunk_head_t *ch;
+
+    printk("    Adding memory range %lx-%lx\n", r_min, r_max);
+
+    /* The buddy lists are addressed in high memory. */
+    r_min = (unsigned long)to_virt(r_min);
+    r_max = (unsigned long)to_virt(r_max);
+    range = r_max - r_min;
+
+    /* Free up the memory we've been given to play with. */
+    map_free(PHYS_PFN(r_min), range >> PAGE_SHIFT);
+
+    while ( range != 0 )
+    {
+        /*
+         * Next chunk is limited by alignment of min, but also
+         * must not be bigger than remaining range.
+         */
+        for ( i = PAGE_SHIFT; (1UL << (i + 1)) <= range; i++ )
+        {
+            if ( r_min & (1UL << i) )
+                break;
+        }
+
+        ch = (chunk_head_t *)r_min;
+        r_min += 1UL << i;
+        range -= 1UL << i;
+        enqueue_elem(ch, i - PAGE_SHIFT);
+    }
+}
+
+void iterate_memory_range(unsigned long min, unsigned long max,
+                          void (*func)(unsigned long, unsigned long))
+{
+    unsigned int m;
+    unsigned long r_min, r_max;
+
+    for ( m = 0; m < e820_entries; m++ )
+    {
+        if ( e820_map[m].type != E820_RAM )
+            continue;
+        if ( e820_map[m].addr + e820_map[m].size >= ULONG_MAX )
+            BUG();
+
+        r_min = e820_map[m].addr;
+        r_max = r_min + e820_map[m].size;
+        if ( r_max <= min || r_min >= max )
+            continue;
+        if ( r_min < min )
+            r_min = min;
+        if ( r_max > max )
+            r_max = max;
+
+        func(r_min, r_max);
+    }
+}
+
 /*
  * Initialise allocator, placing addresses [@min,@max] in free pool.
  * @min and @max are PHYSICAL addresses.
  */
 static void init_page_allocator(unsigned long min, unsigned long max)
 {
-    int i, m;
-    unsigned long range;
-    unsigned long r_min, r_max;
-    chunk_head_t *ch;
+    int i;
 
     printk("MM: Initialise page allocator for %lx(%lx)-%lx(%lx)\n",
            (u_long)to_virt(min), min, (u_long)to_virt(max), max);
@@ -182,50 +240,7 @@ static void init_page_allocator(unsigned long min, 
unsigned long max)
     /* All allocated by default. */
     memset(mm_alloc_bitmap, ~0, mm_alloc_bitmap_size);
 
-    for ( m = 0; m < e820_entries; m++ )
-    {
-        if ( e820_map[m].type != E820_RAM )
-            continue;
-        if ( e820_map[m].addr + e820_map[m].size >= ULONG_MAX )
-            BUG();
-
-        r_min = e820_map[m].addr;
-        r_max = r_min + e820_map[m].size;
-        if ( r_max <= min || r_min >= max )
-            continue;
-        if ( r_min < min )
-            r_min = min;
-        if ( r_max > max )
-            r_max = max;
-
-        printk("    Adding memory range %lx-%lx\n", r_min, r_max);
-
-        /* The buddy lists are addressed in high memory. */
-        r_min = (unsigned long)to_virt(r_min);
-        r_max = (unsigned long)to_virt(r_max);
-        range = r_max - r_min;
-
-        /* Free up the memory we've been given to play with. */
-        map_free(PHYS_PFN(r_min), range >> PAGE_SHIFT);
-
-        while ( range != 0 )
-        {
-            /*
-             * Next chunk is limited by alignment of min, but also
-             * must not be bigger than remaining range.
-             */
-            for ( i = PAGE_SHIFT; (1UL << (i + 1)) <= range; i++ )
-            {
-                if ( r_min & (1UL << i) )
-                    break;
-            }
-
-            ch = (chunk_head_t *)r_min;
-            r_min += 1UL << i;
-            range -= 1UL << i;
-            enqueue_elem(ch, i - PAGE_SHIFT);
-        }
-    }
+    iterate_memory_range(min, max, add_memory_range);
 
     mm_alloc_bitmap_remap();
 }
-- 
2.43.0