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272 righe
9.8 KiB
272 righe
9.8 KiB
#include <pmm.h>
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#include <list.h>
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#include <string.h>
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#include <default_pmm.h>
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/* In the first fit algorithm, the allocator keeps a list of free blocks (known as the free list) and,
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on receiving a request for memory, scans along the list for the first block that is large enough to
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satisfy the request. If the chosen block is significantly larger than that requested, then it is
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usually split, and the remainder added to the list as another free block.
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Please see Page 196~198, Section 8.2 of Yan Wei Ming's chinese book "Data Structure -- C programming language"
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*/
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// LAB2 EXERCISE 1: YOUR CODE
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// you should rewrite functions: default_init,default_init_memmap,default_alloc_pages, default_free_pages.
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/*
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* Details of FFMA
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* (1) Prepare: In order to implement the First-Fit Mem Alloc (FFMA), we should manage the free mem block use some list.
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* The struct free_area_t is used for the management of free mem blocks. At first you should
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* be familiar to the struct list in list.h. struct list is a simple doubly linked list implementation.
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* You should know howto USE: list_init, list_add(list_add_after), list_add_before, list_del, list_next, list_prev
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* Another tricky method is to transform a general list struct to a special struct (such as struct page):
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* you can find some MACRO: le2page (in memlayout.h), (in future labs: le2vma (in vmm.h), le2proc (in proc.h),etc.)
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* (2) default_init: you can reuse the demo default_init fun to init the free_list and set nr_free to 0.
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* free_list is used to record the free mem blocks. nr_free is the total number for free mem blocks.
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* (3) default_init_memmap: CALL GRAPH: kern_init --> pmm_init-->page_init-->init_memmap--> pmm_manager->init_memmap
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* This fun is used to init a free block (with parameter: addr_base, page_number).
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* First you should init each page (in memlayout.h) in this free block, include:
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* p->flags should be set bit PG_property (means this page is valid. In pmm_init fun (in pmm.c),
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* the bit PG_reserved is setted in p->flags)
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* if this page is free and is not the first page of free block, p->property should be set to 0.
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* if this page is free and is the first page of free block, p->property should be set to total num of block.
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* p->ref should be 0, because now p is free and no reference.
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* We can use p->page_link to link this page to free_list, (such as: list_add_before(&free_list, &(p->page_link)); )
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* Finally, we should sum the number of free mem block: nr_free+=n
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* (4) default_alloc_pages: search find a first free block (block size >=n) in free list and reszie the free block, return the addr
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* of malloced block.
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* (4.1) So you should search freelist like this:
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* list_entry_t le = &free_list;
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* while((le=list_next(le)) != &free_list) {
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* ....
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* (4.1.1) In while loop, get the struct page and check the p->property (record the num of free block) >=n?
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* struct Page *p = le2page(le, page_link);
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* if(p->property >= n){ ...
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* (4.1.2) If we find this p, then it' means we find a free block(block size >=n), and the first n pages can be malloced.
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* Some flag bits of this page should be setted: PG_reserved =1, PG_property =0
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* unlink the pages from free_list
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* (4.1.2.1) If (p->property >n), we should re-caluclate number of the the rest of this free block,
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* (such as: le2page(le,page_link))->property = p->property - n;)
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* (4.1.3) re-caluclate nr_free (number of the the rest of all free block)
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* (4.1.4) return p
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* (4.2) If we can not find a free block (block size >=n), then return NULL
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* (5) default_free_pages: relink the pages into free list, maybe merge small free blocks into big free blocks.
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* (5.1) according the base addr of withdrawed blocks, search free list, find the correct position
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* (from low to high addr), and insert the pages. (may use list_next, le2page, list_add_before)
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* (5.2) reset the fields of pages, such as p->ref, p->flags (PageProperty)
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* (5.3) try to merge low addr or high addr blocks. Notice: should change some pages's p->property correctly.
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*/
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free_area_t free_area;
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#define free_list (free_area.free_list)
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#define nr_free (free_area.nr_free)
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static void
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default_init(void) {
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list_init(&free_list);
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nr_free = 0;
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}
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static void
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default_init_memmap(struct Page *base, size_t n) {
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assert(n > 0);
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struct Page *p = base;
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for (; p != base + n; p ++) {
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assert(PageReserved(p));
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p->flags = p->property = 0;
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set_page_ref(p, 0);
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}
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base->property = n;
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SetPageProperty(base);
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nr_free += n;
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list_add(&free_list, &(base->page_link));
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}
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static struct Page *
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default_alloc_pages(size_t n) {
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assert(n > 0);
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if (n > nr_free) {
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return NULL;
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}
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struct Page *page = NULL;
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list_entry_t *le = &free_list;
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while ((le = list_next(le)) != &free_list) {
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struct Page *p = le2page(le, page_link);
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if (p->property >= n) {
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page = p;
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break;
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}
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}
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if (page != NULL) {
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list_del(&(page->page_link));
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if (page->property > n) {
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struct Page *p = page + n;
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p->property = page->property - n;
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list_add(&free_list, &(p->page_link));
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}
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nr_free -= n;
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ClearPageProperty(page);
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}
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return page;
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}
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static void
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default_free_pages(struct Page *base, size_t n) {
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assert(n > 0);
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struct Page *p = base;
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for (; p != base + n; p ++) {
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assert(!PageReserved(p) && !PageProperty(p));
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p->flags = 0;
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set_page_ref(p, 0);
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}
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base->property = n;
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SetPageProperty(base);
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list_entry_t *le = list_next(&free_list);
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while (le != &free_list) {
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p = le2page(le, page_link);
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le = list_next(le);
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if (base + base->property == p) {
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base->property += p->property;
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ClearPageProperty(p);
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list_del(&(p->page_link));
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}
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else if (p + p->property == base) {
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p->property += base->property;
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ClearPageProperty(base);
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base = p;
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list_del(&(p->page_link));
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}
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}
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nr_free += n;
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list_add(&free_list, &(base->page_link));
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}
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static size_t
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default_nr_free_pages(void) {
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return nr_free;
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}
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static void
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basic_check(void) {
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struct Page *p0, *p1, *p2;
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p0 = p1 = p2 = NULL;
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assert((p0 = alloc_page()) != NULL);
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assert((p1 = alloc_page()) != NULL);
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assert((p2 = alloc_page()) != NULL);
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assert(p0 != p1 && p0 != p2 && p1 != p2);
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assert(page_ref(p0) == 0 && page_ref(p1) == 0 && page_ref(p2) == 0);
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assert(page2pa(p0) < npage * PGSIZE);
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assert(page2pa(p1) < npage * PGSIZE);
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assert(page2pa(p2) < npage * PGSIZE);
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list_entry_t free_list_store = free_list;
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list_init(&free_list);
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assert(list_empty(&free_list));
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unsigned int nr_free_store = nr_free;
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nr_free = 0;
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assert(alloc_page() == NULL);
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free_page(p0);
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free_page(p1);
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free_page(p2);
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assert(nr_free == 3);
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assert((p0 = alloc_page()) != NULL);
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assert((p1 = alloc_page()) != NULL);
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assert((p2 = alloc_page()) != NULL);
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assert(alloc_page() == NULL);
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free_page(p0);
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assert(!list_empty(&free_list));
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struct Page *p;
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assert((p = alloc_page()) == p0);
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assert(alloc_page() == NULL);
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assert(nr_free == 0);
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free_list = free_list_store;
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nr_free = nr_free_store;
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free_page(p);
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free_page(p1);
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free_page(p2);
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}
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// LAB2: below code is used to check the first fit allocation algorithm (your EXERCISE 1)
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// NOTICE: You SHOULD NOT CHANGE basic_check, default_check functions!
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static void
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default_check(void) {
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int count = 0, total = 0;
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list_entry_t *le = &free_list;
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while ((le = list_next(le)) != &free_list) {
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struct Page *p = le2page(le, page_link);
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assert(PageProperty(p));
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count ++, total += p->property;
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}
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assert(total == nr_free_pages());
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basic_check();
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struct Page *p0 = alloc_pages(5), *p1, *p2;
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assert(p0 != NULL);
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assert(!PageProperty(p0));
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list_entry_t free_list_store = free_list;
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list_init(&free_list);
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assert(list_empty(&free_list));
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assert(alloc_page() == NULL);
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unsigned int nr_free_store = nr_free;
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nr_free = 0;
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free_pages(p0 + 2, 3);
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assert(alloc_pages(4) == NULL);
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assert(PageProperty(p0 + 2) && p0[2].property == 3);
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assert((p1 = alloc_pages(3)) != NULL);
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assert(alloc_page() == NULL);
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assert(p0 + 2 == p1);
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p2 = p0 + 1;
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free_page(p0);
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free_pages(p1, 3);
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assert(PageProperty(p0) && p0->property == 1);
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assert(PageProperty(p1) && p1->property == 3);
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assert((p0 = alloc_page()) == p2 - 1);
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free_page(p0);
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assert((p0 = alloc_pages(2)) == p2 + 1);
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free_pages(p0, 2);
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free_page(p2);
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assert((p0 = alloc_pages(5)) != NULL);
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assert(alloc_page() == NULL);
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assert(nr_free == 0);
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nr_free = nr_free_store;
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free_list = free_list_store;
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free_pages(p0, 5);
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le = &free_list;
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while ((le = list_next(le)) != &free_list) {
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struct Page *p = le2page(le, page_link);
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count --, total -= p->property;
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}
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assert(count == 0);
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assert(total == 0);
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}
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const struct pmm_manager default_pmm_manager = {
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.name = "default_pmm_manager",
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.init = default_init,
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.init_memmap = default_init_memmap,
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.alloc_pages = default_alloc_pages,
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.free_pages = default_free_pages,
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.nr_free_pages = default_nr_free_pages,
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.check = default_check,
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};
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