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#ifndef _LINUX_PAGE_REF_H
#define _LINUX_PAGE_REF_H
#include <linux/atomic.h>
#include <linux/mm_types.h>
#include <linux/page-flags.h>
static inline struct page *compound_head_by_tail(struct page *tail)
{
struct page *head = tail->first_page;
/*
* page->first_page may be a dangling pointer to an old
* compound page, so recheck that it is still a tail
* page before returning.
*/
smp_rmb();
if (likely(PageTail(tail)))
return head;
return tail;
}
static inline struct page *compound_head(struct page *page)
{
if (unlikely(PageTail(page)))
return compound_head_by_tail(page);
return page;
}
static inline int page_ref_count(struct page *page)
{
return atomic_read(&page->_count);
}
static inline int page_count(struct page *page)
{
return atomic_read(&compound_head(page)->_count);
}
static inline void set_page_count(struct page *page, int v)
{
atomic_set(&page->_count, v);
}
/*
* Setup the page count before being freed into the page allocator for
* the first time (boot or memory hotplug)
*/
static inline void init_page_count(struct page *page)
{
set_page_count(page, 1);
}
static inline void page_ref_add(struct page *page, int nr)
{
atomic_add(nr, &page->_count);
}
static inline void page_ref_sub(struct page *page, int nr)
{
atomic_sub(nr, &page->_count);
}
static inline void page_ref_inc(struct page *page)
{
atomic_inc(&page->_count);
}
static inline void page_ref_dec(struct page *page)
{
atomic_dec(&page->_count);
}
static inline int page_ref_sub_and_test(struct page *page, int nr)
{
return atomic_sub_and_test(nr, &page->_count);
}
static inline int page_ref_dec_and_test(struct page *page)
{
return atomic_dec_and_test(&page->_count);
}
static inline int page_ref_dec_return(struct page *page)
{
return atomic_dec_return(&page->_count);
}
static inline int page_ref_add_unless(struct page *page, int nr, int u)
{
return atomic_add_unless(&page->_count, nr, u);
}
static inline int page_ref_freeze(struct page *page, int count)
{
return likely(atomic_cmpxchg(&page->_count, count, 0) == count);
}
static inline void page_ref_unfreeze(struct page *page, int count)
{
VM_BUG_ON_PAGE(page_count(page) != 0, page);
VM_BUG_ON(count == 0);
atomic_set(&page->_count, count);
}
#endif
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