Linux Kernel 3.0.8 內存管理函數

相關代碼如下：

#define alloc_pages(gfp_mask, order) alloc_pages_node(numa_node_id(), gfp_mask, order)
#define alloc_page_vma(gfp_mask, vma, addr) alloc_pages(gfp_mask, 0)
#define alloc_page(gfp_mask) alloc_pages(gfp_mask, 0)

#define __get_free_page(gfp_mask) __get_free_pages((gfp_mask),0)
#define __get_dma_pages(gfp_mask, order) __get_free_pages((gfp_mask) | GFP_DMA,(order))

#define pfn_to_page(pfn) (mem_map + ((pfn) - PHYS_PFN_OFFSET))
#define page_to_pfn(page) ((unsigned long)((page) - mem_map) + PHYS_PFN_OFFSET)
#define pfn_valid(pfn) ((pfn) >= PHYS_PFN_OFFSET && (pfn) < (PHYS_PFN_OFFSET + max_mapnr))

#define phys_to_page(phys) (pfn_to_page(phys >> PAGE_SHIFT))
#define page_to_phys(page) (page_to_pfn(page) << PAGE_SHIFT)

#define virt_to_page(kaddr) pfn_to_page(__pa(kaddr) >> PAGE_SHIFT)
#define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT)

1）__get_free_pages實現代碼如下，它返回頁的虛擬地址：

1. unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order)
2. {
3. struct page *page;
5. /*
6. * __get_free_pages() returns a 32-bit address, which cannot represent
7. * a highmem page
8. */
9. VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
11. page = alloc_pages(gfp_mask, order);
12. if (!page)
13. return 0;
14. return (unsigned long) page_address(page);
15. }

1. /**
2. * page_address - get the mapped virtual address of a page
3. * @page: &struct page to get the virtual address of
4. *
5. * Returns the page's virtual address.
6. */
7. void *page_address(struct page *page)
8. {
9. unsigned long flags;
10. void *ret;
11. struct page_address_slot *pas;
13. if (!PageHighMem(page))
14. return lowmem_page_address(page);
16. pas = page_slot(page);
17. ret = NULL;
18. spin_lock_irqsave(&pas->lock, flags);
19. if (!list_empty(&pas->lh)) {
20. struct page_address_map *pam;
22. list_for_each_entry(pam, &pas->lh, list) {
23. if (pam->page == page) {
24. ret = pam->virtual;
25. goto done;
26. }
27. }
28. }
29. done:
30. spin_unlock_irqrestore(&pas->lock, flags);
31. return ret;
32. }

1. static __always_inline void *lowmem_page_address(struct page *page)
2. {
3. return __va(PFN_PHYS(page_to_pfn(page)));
4. }

2）alloc_pages_node

1. static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
2. unsigned int order)
3. {
4. /* Unknown node is current node */
5. if (nid < 0)
6. nid = numa_node_id();
8. return __alloc_pages(gfp_mask, order, node_zonelist(nid, gfp_mask));
9. }