C++ put_page_testzero函数代码示例

static void put_compound_page(struct page *page)
{
	if (unlikely(PageTail(page))) {
		/* __split_huge_page_refcount can run under us */
		struct page *page_head = compound_trans_head(page);

		if (likely(page != page_head &&
			   get_page_unless_zero(page_head))) {
			unsigned long flags;
			/*
			 * page_head wasn't a dangling pointer but it
			 * may not be a head page anymore by the time
			 * we obtain the lock. That is ok as long as it
			 * can't be freed from under us.
			 */
			flags = compound_lock_irqsave(page_head);
			if (unlikely(!PageTail(page))) {
				/* __split_huge_page_refcount run before us */
				compound_unlock_irqrestore(page_head, flags);
				VM_BUG_ON(PageHead(page_head));
				if (put_page_testzero(page_head))
					__put_single_page(page_head);
			out_put_single:
				if (put_page_testzero(page))
					__put_single_page(page);
				return;
			}
			VM_BUG_ON(page_head != page->first_page);
			/*
			 * We can release the refcount taken by
			 * get_page_unless_zero() now that
			 * __split_huge_page_refcount() is blocked on
			 * the compound_lock.
			 */
			if (put_page_testzero(page_head))
				VM_BUG_ON(1);
			/* __split_huge_page_refcount will wait now */
			VM_BUG_ON(page_mapcount(page) <= 0);
			atomic_dec(&page->_mapcount);
			VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
			VM_BUG_ON(atomic_read(&page->_count) != 0);
			compound_unlock_irqrestore(page_head, flags);
			if (put_page_testzero(page_head)) {
				if (PageHead(page_head))
					__put_compound_page(page_head);
				else
					__put_single_page(page_head);
			}
		} else {
			/* page_head is a dangling pointer */
			VM_BUG_ON(PageTail(page));
			goto out_put_single;
		}
	} else if (put_page_testzero(page)) {
		if (PageHead(page))
			__put_compound_page(page);
		else
			__put_single_page(page);
	}
}

void put_page(struct page *page)
{
	if (unlikely(PageCompound(page))) {
		page = (struct page *)page_private(page);
		if (put_page_testzero(page)) {
			void (*dtor)(struct page *page);

			dtor = (void (*)(struct page *))page[1].mapping;
			(*dtor)(page);
		}
		return;
	}
	if (put_page_testzero(page))
		__page_cache_release(page);
}

/* Cleanup a mapping */
static void fb_vma_free(struct pme_fb_vma *node)
{
	int order, num_pages;
	struct page *p;
	if (atomic_dec_and_test(&node->ref_count)) {
		/* This buffer can be recycled
		 * (Buffers can be NULL in the case where
		 * the mapped area is an iovec structure) */
		if (node->buffers)
			pme_fbchain_recycle(node->buffers);

		if (node->iovec_pages) {
			order = get_order(node->kmem_size);
			if (order) {
				p = node->iovec_pages;
				num_pages = 1 << order;
				while (num_pages--) {
					put_page_testzero(p);
					p++;
				}
			}
			__free_pages(node->iovec_pages, order);
		}
		vfree(node);
	}
}

static void vmlfb_free_vram_area(struct vram_area *va)
{
	unsigned long j;

	if (va->logical) {

		/*
		 * Reset the linear kernel map caching policy.
		 */

		set_pages_wb(virt_to_page(va->logical),
				 va->size >> PAGE_SHIFT);

		/*
		 * Decrease the usage count on the pages we've used
		 * to compensate for upping when allocating.
		 */

		for (j = va->logical; j < va->logical + va->size;
		     j += PAGE_SIZE) {
			(void)put_page_testzero(virt_to_page(j));
		}

		printk(KERN_DEBUG MODULE_NAME
		       ": Freeing %ld bytes vram area at 0x%08lx\n",
		       va->size, va->phys);
		free_pages(va->logical, va->order);

		va->logical = 0;
	}

/**
 * Two special cases here: we could avoid taking compound_lock_irqsave
 * and could skip the tail refcounting(in _mapcount).
 *
 * 1. Hugetlbfs page:
 *
 *    PageHeadHuge will remain true until the compound page
 *    is released and enters the buddy allocator, and it could
 *    not be split by __split_huge_page_refcount().
 *
 *    So if we see PageHeadHuge set, and we have the tail page pin,
 *    then we could safely put head page.
 *
 * 2. Slab THP page:
 *
 *    PG_slab is cleared before the slab frees the head page, and
 *    tail pin cannot be the last reference left on the head page,
 *    because the slab code is free to reuse the compound page
 *    after a kfree/kmem_cache_free without having to check if
 *    there's any tail pin left.  In turn all tail pinsmust be always
 *    released while the head is still pinned by the slab code
 *    and so we know PG_slab will be still set too.
 *
 *    So if we see PageSlab set, and we have the tail page pin,
 *    then we could safely put head page.
 */
static __always_inline
void put_unrefcounted_compound_page(struct page *page_head, struct page *page)
{
	/*
	 * If @page is a THP tail, we must read the tail page
	 * flags after the head page flags. The
	 * __split_huge_page_refcount side enforces write memory barriers
	 * between clearing PageTail and before the head page
	 * can be freed and reallocated.
	 */
	smp_rmb();
	if (likely(PageTail(page))) {
		/*
		 * __split_huge_page_refcount cannot race
		 * here, see the comment above this function.
		 */
		VM_BUG_ON_PAGE(!PageHead(page_head), page_head);
		if (put_page_testzero(page_head)) {
			/*
			 * If this is the tail of a slab THP page,
			 * the tail pin must not be the last reference
			 * held on the page, because the PG_slab cannot
			 * be cleared before all tail pins (which skips
			 * the _mapcount tail refcounting) have been
			 * released.
			 *
			 * If this is the tail of a hugetlbfs page,
			 * the tail pin may be the last reference on
			 * the page instead, because PageHeadHuge will
			 * not go away until the compound page enters
			 * the buddy allocator.
			 */
			VM_BUG_ON_PAGE(PageSlab(page_head), page_head);
			__put_compound_page(page_head);
		}
	} else
		/*
		 * __split_huge_page_refcount run before us,
		 * @page was a THP tail. The split @page_head
		 * has been freed and reallocated as slab or
		 * hugetlbfs page of smaller order (only
		 * possible if reallocated as slab on x86).
		 */
		if (put_page_testzero(page))
			__put_single_page(page);
}

void pte_fragment_free(unsigned long *table, int kernel)
{
	struct page *page = virt_to_page(table);
	if (put_page_testzero(page)) {
		if (!kernel)
			pgtable_page_dtor(page);
		free_hot_cold_page(page, 0);
	}
}

/**
 * release_pages:释放pages页框数组(只有count = 0时,才正真的被回收)
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	struct pagevec pages_to_free;
	struct zone *zone = NULL;
	unsigned long uninitialized_var(flags);

	pagevec_init(&pages_to_free, cold);
	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		/*减少page的引用次数*/
		if (!put_page_testzero(page))
			continue;

		/*page的引用次数为0,则page从zone LRU链表中删除*/
		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}
			VM_BUG_ON(!PageLRU(page));
			/*清空页的LRU属性*/
			__ClearPageLRU(page);
			del_page_from_lru(zone, page);
		}

		/*page加入到pages_to_free页缓存中*/
		if (!pagevec_add(&pages_to_free, page)) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			__pagevec_free(&pages_to_free);
			pagevec_reinit(&pages_to_free);
  		}
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	pagevec_free(&pages_to_free);
}

static void put_compound_page(struct page *page)
{
	page = (struct page *)page_private(page);
	if (put_page_testzero(page)) {
		void (*dtor)(struct page *page);

		dtor = (void (*)(struct page *))page[1].lru.next;
		(*dtor)(page);
	}
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_inactive_list(): we recheck
 * the page count inside the lock to see whether shrink_inactive_list()
 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 * will free it.
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	struct pagevec pages_to_free;
	struct zone *zone = NULL;
	unsigned long uninitialized_var(flags);

	pagevec_init(&pages_to_free, cold);
	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		if (!put_page_testzero(page))
			continue;

		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}
			VM_BUG_ON(!PageLRU(page));
			__ClearPageLRU(page);
			del_page_from_lru(zone, page);
		} else if (PageIONBacked(page)) {
			ClearPageActive(page);
			ClearPageUnevictable(page);
		}

		if (!pagevec_add(&pages_to_free, page)) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			__pagevec_free(&pages_to_free);
			pagevec_reinit(&pages_to_free);
  		}
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	pagevec_free(&pages_to_free);
}

void __homecache_free_pages(struct page *page, unsigned int order)
{
	if (put_page_testzero(page)) {
		homecache_change_page_home(page, order, PAGE_HOME_HASH);
		if (order == 0) {
			free_hot_cold_page(page, false);
		} else {
			init_page_count(page);
			__free_pages(page, order);
		}
	}
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_cache(): we recheck the
 * page count inside the lock to see whether shrink_cache grabbed the page
 * via the LRU.  If it did, give up: shrink_cache will free it.
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	struct pagevec pages_to_free;
	struct zone *zone = NULL;
	unsigned long uninitialized_var(flags);

	pagevec_init(&pages_to_free, cold);
	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}
        // dyc: if page->ref not zero, continue
		if (!put_page_testzero(page))
			continue;
        // dyc: if in url, remove from it
		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);
			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}
			VM_BUG_ON(!PageLRU(page));
			__ClearPageLRU(page);
			del_page_from_lru(zone, page);
		}
        // dyc: if no space available after adding
		if (!pagevec_add(&pages_to_free, page)) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
            // dyc: return page to buddy system
			__pagevec_free(&pages_to_free);
			pagevec_reinit(&pages_to_free);
  		}
	} // for (i = 0; i < nr; i++)
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	pagevec_free(&pages_to_free);
}

void homecache_free_pages(unsigned long addr, unsigned int order)
{
	struct page *page;

	if (addr == 0)
		return;

	VM_BUG_ON(!virt_addr_valid((void *)addr));
	page = virt_to_page((void *)addr);
	if (put_page_testzero(page)) {
		int pages = (1 << order);
		homecache_change_page_home(page, order, initial_page_home());
		while (pages--)
			__free_page(page++);
	}
}

/*
 * pagevec_release() for pages which are known to not be on the LRU
 *
 * This function reinitialises the caller's pagevec.
 */
void __pagevec_release_nonlru(struct pagevec *pvec)
{
	int i;
	struct pagevec pages_to_free;

	pagevec_init(&pages_to_free, pvec->cold);
	for (i = 0; i < pagevec_count(pvec); i++) {
		struct page *page = pvec->pages[i];

		VM_BUG_ON(PageLRU(page));
		if (put_page_testzero(page))
			pagevec_add(&pages_to_free, page);
	}
	pagevec_free(&pages_to_free);
	pagevec_reinit(pvec);
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_cache(): we recheck the
 * page count inside the lock to see whether shrink_cache grabbed the page
 * via the LRU.  If it did, give up: shrink_cache will free it.
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	struct pagevec pages_to_free;
	struct zone *zone = NULL;

	pagevec_init(&pages_to_free, cold);
	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];
		struct zone *pagezone;

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irq(&zone->lru_lock);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		if (!put_page_testzero(page))
			continue;

		pagezone = page_zone(page);
		if (pagezone != zone) {
			if (zone)
				spin_unlock_irq(&zone->lru_lock);
			zone = pagezone;
			spin_lock_irq(&zone->lru_lock);
		}
		if (TestClearPageLRU(page))
			del_page_from_lru(zone, page);
		if (page_count(page) == 0) {
			if (!pagevec_add(&pages_to_free, page)) {
				spin_unlock_irq(&zone->lru_lock);
				__pagevec_free(&pages_to_free);
				pagevec_reinit(&pages_to_free);
				zone = NULL;	/* No lock is held */
			}
		}
	}
	if (zone)
		spin_unlock_irq(&zone->lru_lock);

	pagevec_free(&pages_to_free);
}

/*
 * Batched page_cache_release().  Decrement the reference count on all the
 * passed pages.  If it fell to zero then remove the page from the LRU and
 * free it.
 *
 * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 * for the remainder of the operation.
 *
 * The locking in this function is against shrink_inactive_list(): we recheck
 * the page count inside the lock to see whether shrink_inactive_list()
 * grabbed the page via the LRU.  If it did, give up: shrink_inactive_list()
 * will free it.
 */
void release_pages(struct page **pages, int nr, int cold)
{
	int i;
	LIST_HEAD(pages_to_free);
	struct zone *zone = NULL;
	unsigned long uninitialized_var(flags);

	for (i = 0; i < nr; i++) {
		struct page *page = pages[i];

		if (unlikely(PageCompound(page))) {
			if (zone) {
				spin_unlock_irqrestore(&zone->lru_lock, flags);
				zone = NULL;
			}
			put_compound_page(page);
			continue;
		}

		if (!put_page_testzero(page))
			continue;

		if (PageLRU(page)) {
			struct zone *pagezone = page_zone(page);

			if (pagezone != zone) {
				if (zone)
					spin_unlock_irqrestore(&zone->lru_lock,
									flags);
				zone = pagezone;
				spin_lock_irqsave(&zone->lru_lock, flags);
			}
			VM_BUG_ON(!PageLRU(page));
			__ClearPageLRU(page);
			del_page_from_lru_list(zone, page, page_off_lru(page));
		}

		list_add(&page->lru, &pages_to_free);
	}
	if (zone)
		spin_unlock_irqrestore(&zone->lru_lock, flags);

	free_hot_cold_page_list(&pages_to_free, cold);
}