页属性初始化时全为MIGRATE_MOVABLE？？

xinghun_4

深入linux架构165页书上说，memap_init_zone函数将所有页最初都标记为可移动的，但是从代码中，我觉得一开始并没用这样设置呀！！！！

1. void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
   
2.                 unsigned long start_pfn, enum memmap_context context)
   
3. {
   
4.         struct page *page;
   
5.         unsigned long end_pfn = start_pfn + size;
   
6.         unsigned long pfn;
   
7. 
   
8.         for (pfn = start_pfn; pfn < end_pfn; pfn++) {
   
9.                 /*
   
10.                  * There can be holes in boot-time mem_map[]s
    
11.                  * handed to this function.  They do not
    
12.                  * exist on hotplugged memory.
    
13.                  */
    
14.                 if (context == MEMMAP_EARLY) {
    
15.                         if (!early_pfn_valid(pfn))
    
16.                                 continue;
    
17.                         if (!early_pfn_in_nid(pfn, nid))
    
18.                                 continue;
    
19.                 }
    
20.                 page = pfn_to_page(pfn);
    
21.                 set_page_links(page, zone, nid, pfn);
    
22.                 init_page_count(page);
    
23.                 reset_page_mapcount(page);
    
24.                 SetPageReserved(page); /*???????????????????????*/
    
25.                          /*
    
26.                  * Mark the block movable so that blocks are reserved for
    
27.                  * movable at startup. This will force kernel allocations
    
28.                  * to reserve their blocks rather than leaking throughout
    
29.                  * the address space during boot when many long-lived
    
30.                  * kernel allocations are made. Later some blocks near
    
31.                  * the start are marked MIGRATE_RESERVE by
    
32.                  * setup_zone_migrate_reserve()
    
33.                  */
    
34.                 if ((pfn & (pageblock_nr_pages-1)))/*???????????????????????????*/
    
35.                         set_pageblock_migratetype(page, MIGRATE_MOVABLE);

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从上面问号的地方可以看出，我倒觉得一开始，所有页都标记为了reserved的了，是吗？求解释？求牛人指教！！！！