/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Macros for manipulating and testing page->flags
 */

#ifndef PAGE_FLAGS_H
#define PAGE_FLAGS_H

#include <linux/types.h>
#include <linux/bug.h>
#include <linux/mmdebug.h>
#ifndef __GENERATING_BOUNDS_H
#include <linux/mm_types.h>
#include <generated/bounds.h>
#endif /* !__GENERATING_BOUNDS_H */

/*
 * Various page->flags bits:
 *
 * PG_reserved is set for special pages, which can never be swapped out. Some
 * of them might not even exist...
 *
 * The PG_private bitflag is set on pagecache pages if they contain filesystem
 * specific data (which is normally at page->private). It can be used by
 * private allocations for its own usage.
 *
 * During initiation of disk I/O, PG_locked is set. This bit is set before I/O
 * and cleared when writeback _starts_ or when read _completes_. PG_writeback
 * is set before writeback starts and cleared when it finishes.
 *
 * PG_locked also pins a page in pagecache, and blocks truncation of the file
 * while it is held.
 *
 * page_waitqueue(page) is a wait queue of all tasks waiting for the page
 * to become unlocked.
 *
 * PG_swapbacked is set when a page uses swap as a backing storage.  This are
 * usually PageAnon or shmem pages but please note that even anonymous pages
 * might lose their PG_swapbacked flag when they simply can be dropped (e.g. as
 * a result of MADV_FREE).
 *
 * PG_uptodate tells whether the page's contents is valid.  When a read
 * completes, the page becomes uptodate, unless a disk I/O error happened.
 *
 * PG_referenced, PG_reclaim are used for page reclaim for anonymous and
 * file-backed pagecache (see mm/vmscan.c).
 *
 * PG_error is set to indicate that an I/O error occurred on this page.
 *
 * PG_arch_1 is an architecture specific page state bit.  The generic code
 * guarantees that this bit is cleared for a page when it first is entered into
 * the page cache.
 *
 * PG_hwpoison indicates that a page got corrupted in hardware and contains
 * data with incorrect ECC bits that triggered a machine check. Accessing is
 * not safe since it may cause another machine check. Don't touch!
 */

/*
 * Don't use the *_dontuse flags.  Use the macros.  Otherwise you'll break
 * locked- and dirty-page accounting.
 *
 * The page flags field is split into two parts, the main flags area
 * which extends from the low bits upwards, and the fields area which
 * extends from the high bits downwards.
 *
 *  | FIELD | ... | FLAGS |
 *  N-1           ^       0
 *               (NR_PAGEFLAGS)
 *
 * The fields area is reserved for fields mapping zone, node (for NUMA) and
 * SPARSEMEM section (for variants of SPARSEMEM that require section ids like
 * SPARSEMEM_EXTREME with !SPARSEMEM_VMEMMAP).
 */
enum pageflags {
        PG_locked,              /* Page is locked. Don't touch. */
        PG_error,
        PG_referenced,
        PG_uptodate,
        PG_dirty,
        PG_lru,
        PG_active,
        PG_waiters,             /* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
        PG_slab,
        PG_owner_priv_1,        /* Owner use. If pagecache, fs may use*/
        PG_arch_1,
        PG_reserved,
        PG_private,             /* If pagecache, has fs-private data */
        PG_private_2,           /* If pagecache, has fs aux data */
        PG_writeback,           /* Page is under writeback */
        PG_head,                /* A head page */
        PG_mappedtodisk,        /* Has blocks allocated on-disk */
        PG_reclaim,             /* To be reclaimed asap */
        PG_swapbacked,          /* Page is backed by RAM/swap */
        PG_unevictable,         /* Page is "unevictable"  */
#ifdef CONFIG_MMU
        PG_mlocked,             /* Page is vma mlocked */
#endif
#ifdef CONFIG_ARCH_USES_PG_UNCACHED
        PG_uncached,            /* Page has been mapped as uncached */
#endif
#ifdef CONFIG_MEMORY_FAILURE
        PG_hwpoison,            /* hardware poisoned page. Don't touch */
#endif
#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
        PG_young,
        PG_idle,
#endif
#ifndef __GENKSYMS__
        /*
         * RHEL8: New page flags should be put here to avoid changing
         * kABI signature.
         */
        PG_workingset,
#endif
        __NR_PAGEFLAGS,

        /* Filesystems */
        PG_checked = PG_owner_priv_1,

        /* SwapBacked */
        PG_swapcache = PG_owner_priv_1, /* Swap page: swp_entry_t in private */

        /* Two page bits are conscripted by FS-Cache to maintain local caching
         * state.  These bits are set on pages belonging to the netfs's inodes
         * when those inodes are being locally cached.
         */
        PG_fscache = PG_private_2,      /* page backed by cache */

        /* XEN */
        /* Pinned in Xen as a read-only pagetable page. */
        PG_pinned = PG_owner_priv_1,
        /* Pinned as part of domain save (see xen_mm_pin_all()). */
        PG_savepinned = PG_dirty,
        /* Has a grant mapping of another (foreign) domain's page. */
        PG_foreign = PG_owner_priv_1,

        /* SLOB */
        PG_slob_free = PG_private,

        /* Compound pages. Stored in first tail page's flags */
        PG_double_map = PG_private_2,

        /* non-lru isolated movable page */
        PG_isolated = PG_reclaim,

        /* Only valid for buddy pages. Used to track pages that are reported */
        PG_reported = PG_uptodate,
};

#ifndef __GENERATING_BOUNDS_H

struct page;    /* forward declaration */

static inline struct page *compound_head(struct page *page)
{
        unsigned long head = READ_ONCE(page->compound_head);

        if (unlikely(head & 1))
                return (struct page *) (head - 1);
        return page;
}

static __always_inline int PageTail(struct page *page)
{
        return READ_ONCE(page->compound_head) & 1;
}

static __always_inline int PageCompound(struct page *page)
{
        return test_bit(PG_head, &page->flags) || PageTail(page);
}

#define PAGE_POISON_PATTERN     -1l
static inline int PagePoisoned(const struct page *page)
{
        return page->flags == PAGE_POISON_PATTERN;
}

#ifdef CONFIG_DEBUG_VM
void page_init_poison(struct page *page, size_t size);
#else
static inline void page_init_poison(struct page *page, size_t size)
{
}
#endif

/*
 * Page flags policies wrt compound pages
 *
 * PF_POISONED_CHECK
 *     check if this struct page poisoned/uninitialized
 *
 * PF_ANY:
 *     the page flag is relevant for small, head and tail pages.
 *
 * PF_HEAD:
 *     for compound page all operations related to the page flag applied to
 *     head page.
 *
 * PF_ONLY_HEAD:
 *     for compound page, callers only ever operate on the head page.
 *
 * PF_NO_TAIL:
 *     modifications of the page flag must be done on small or head pages,
 *     checks can be done on tail pages too.
 *
 * PF_NO_COMPOUND:
 *     the page flag is not relevant for compound pages.
 */
#define PF_POISONED_CHECK(page) ({                                      \
                VM_BUG_ON_PGFLAGS(PagePoisoned(page), page);            \
                page; })
#define PF_ANY(page, enforce)   PF_POISONED_CHECK(page)
#define PF_HEAD(page, enforce)  PF_POISONED_CHECK(compound_head(page))
#define PF_ONLY_HEAD(page, enforce) ({                                  \
                VM_BUG_ON_PGFLAGS(PageTail(page), page);                \
                PF_POISONED_CHECK(page); })
#define PF_NO_TAIL(page, enforce) ({                                    \
                VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page);     \
                PF_POISONED_CHECK(compound_head(page)); })
#define PF_NO_COMPOUND(page, enforce) ({                                \
                VM_BUG_ON_PGFLAGS(enforce && PageCompound(page), page); \
                PF_POISONED_CHECK(page); })

/*
 * Macros to create function definitions for page flags
 */
#define TESTPAGEFLAG(uname, lname, policy)                              \
static __always_inline int Page##uname(struct page *page)               \
        { return test_bit(PG_##lname, &policy(page, 0)->flags); }

#define SETPAGEFLAG(uname, lname, policy)                               \
static __always_inline void SetPage##uname(struct page *page)           \
        { set_bit(PG_##lname, &policy(page, 1)->flags); }

#define CLEARPAGEFLAG(uname, lname, policy)                             \
static __always_inline void ClearPage##uname(struct page *page)         \
        { clear_bit(PG_##lname, &policy(page, 1)->flags); }

#define __SETPAGEFLAG(uname, lname, policy)                             \
static __always_inline void __SetPage##uname(struct page *page)         \
        { __set_bit(PG_##lname, &policy(page, 1)->flags); }

#define __CLEARPAGEFLAG(uname, lname, policy)                           \
static __always_inline void __ClearPage##uname(struct page *page)       \
        { __clear_bit(PG_##lname, &policy(page, 1)->flags); }

#define TESTSETFLAG(uname, lname, policy)                               \
static __always_inline int TestSetPage##uname(struct page *page)        \
        { return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }

#define TESTCLEARFLAG(uname, lname, policy)                             \
static __always_inline int TestClearPage##uname(struct page *page)      \
        { return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }

#define PAGEFLAG(uname, lname, policy)                                  \
        TESTPAGEFLAG(uname, lname, policy)                              \
        SETPAGEFLAG(uname, lname, policy)                               \
        CLEARPAGEFLAG(uname, lname, policy)

#define __PAGEFLAG(uname, lname, policy)                                \
        TESTPAGEFLAG(uname, lname, policy)                              \
        __SETPAGEFLAG(uname, lname, policy)                             \
        __CLEARPAGEFLAG(uname, lname, policy)

#define TESTSCFLAG(uname, lname, policy)                                \
        TESTSETFLAG(uname, lname, policy)                               \
        TESTCLEARFLAG(uname, lname, policy)

#define TESTPAGEFLAG_FALSE(uname)                                       \
static inline int Page##uname(const struct page *page) { return 0; }

#define SETPAGEFLAG_NOOP(uname)                                         \
static inline void SetPage##uname(struct page *page) {  }

#define CLEARPAGEFLAG_NOOP(uname)                                       \
static inline void ClearPage##uname(struct page *page) {  }

#define __CLEARPAGEFLAG_NOOP(uname)                                     \
static inline void __ClearPage##uname(struct page *page) {  }

#define TESTSETFLAG_FALSE(uname)                                        \
static inline int TestSetPage##uname(struct page *page) { return 0; }

#define TESTCLEARFLAG_FALSE(uname)                                      \
static inline int TestClearPage##uname(struct page *page) { return 0; }

#define PAGEFLAG_FALSE(uname) TESTPAGEFLAG_FALSE(uname)                 \
        SETPAGEFLAG_NOOP(uname) CLEARPAGEFLAG_NOOP(uname)

#define TESTSCFLAG_FALSE(uname)                                         \
        TESTSETFLAG_FALSE(uname) TESTCLEARFLAG_FALSE(uname)

__PAGEFLAG(Locked, locked, PF_NO_TAIL)
PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD)
PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND)
PAGEFLAG(Referenced, referenced, PF_HEAD)
        TESTCLEARFLAG(Referenced, referenced, PF_HEAD)
        __SETPAGEFLAG(Referenced, referenced, PF_HEAD)
PAGEFLAG(Dirty, dirty, PF_HEAD) TESTSCFLAG(Dirty, dirty, PF_HEAD)
        __CLEARPAGEFLAG(Dirty, dirty, PF_HEAD)
PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(LRU, lru, PF_HEAD)
        TESTCLEARFLAG(LRU, lru, PF_HEAD)
PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD)
        TESTCLEARFLAG(Active, active, PF_HEAD)
PAGEFLAG(Workingset, workingset, PF_HEAD)
        TESTCLEARFLAG(Workingset, workingset, PF_HEAD)
__PAGEFLAG(Slab, slab, PF_NO_TAIL)
__PAGEFLAG(SlobFree, slob_free, PF_NO_TAIL)
PAGEFLAG(Checked, checked, PF_NO_COMPOUND)         /* Used by some filesystems */

/* Xen */
PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
        TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);

PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
        __CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
        __SETPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
PAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
        __CLEARPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)
        __SETPAGEFLAG(SwapBacked, swapbacked, PF_NO_TAIL)

/*
 * Private page markings that may be used by the filesystem that owns the page
 * for its own purposes.
 * - PG_private and PG_private_2 cause releasepage() and co to be invoked
 */
PAGEFLAG(Private, private, PF_ANY) __SETPAGEFLAG(Private, private, PF_ANY)
        __CLEARPAGEFLAG(Private, private, PF_ANY)
PAGEFLAG(Private2, private_2, PF_ANY) TESTSCFLAG(Private2, private_2, PF_ANY)
PAGEFLAG(OwnerPriv1, owner_priv_1, PF_ANY)
        TESTCLEARFLAG(OwnerPriv1, owner_priv_1, PF_ANY)

/*
 * Only test-and-set exist for PG_writeback.  The unconditional operators are
 * risky: they bypass page accounting.
 */
TESTPAGEFLAG(Writeback, writeback, PF_NO_TAIL)
        TESTSCFLAG(Writeback, writeback, PF_NO_TAIL)
PAGEFLAG(MappedToDisk, mappedtodisk, PF_NO_TAIL)

/* PG_readahead is only used for reads; PG_reclaim is only for writes */
PAGEFLAG(Reclaim, reclaim, PF_NO_TAIL)
        TESTCLEARFLAG(Reclaim, reclaim, PF_NO_TAIL)
PAGEFLAG(Readahead, reclaim, PF_NO_COMPOUND)
        TESTCLEARFLAG(Readahead, reclaim, PF_NO_COMPOUND)

#ifdef CONFIG_HIGHMEM
/*
 * Must use a macro here due to header dependency issues. page_zone() is not
 * available at this point.
 */
#define PageHighMem(__p) is_highmem_idx(page_zonenum(__p))
#else
PAGEFLAG_FALSE(HighMem)
#endif

#ifdef CONFIG_SWAP
static __always_inline int PageSwapCache(struct page *page)
{
#ifdef CONFIG_THP_SWAP
        page = compound_head(page);
#endif
        return PageSwapBacked(page) && test_bit(PG_swapcache, &page->flags);

}
SETPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
CLEARPAGEFLAG(SwapCache, swapcache, PF_NO_TAIL)
#else
PAGEFLAG_FALSE(SwapCache)
#endif

PAGEFLAG(Unevictable, unevictable, PF_HEAD)
        __CLEARPAGEFLAG(Unevictable, unevictable, PF_HEAD)
        TESTCLEARFLAG(Unevictable, unevictable, PF_HEAD)

#ifdef CONFIG_MMU
PAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
        __CLEARPAGEFLAG(Mlocked, mlocked, PF_NO_TAIL)
        TESTSCFLAG(Mlocked, mlocked, PF_NO_TAIL)
#else
PAGEFLAG_FALSE(Mlocked) __CLEARPAGEFLAG_NOOP(Mlocked)
        TESTSCFLAG_FALSE(Mlocked)
#endif

#ifdef CONFIG_ARCH_USES_PG_UNCACHED
PAGEFLAG(Uncached, uncached, PF_NO_COMPOUND)
#else
PAGEFLAG_FALSE(Uncached)
#endif

#ifdef CONFIG_MEMORY_FAILURE
PAGEFLAG(HWPoison, hwpoison, PF_ANY)
TESTSCFLAG(HWPoison, hwpoison, PF_ANY)
#define __PG_HWPOISON (1UL << PG_hwpoison)
extern bool take_page_off_buddy(struct page *page);
#else
PAGEFLAG_FALSE(HWPoison)
#define __PG_HWPOISON 0
#endif

#if defined(CONFIG_IDLE_PAGE_TRACKING) && defined(CONFIG_64BIT)
TESTPAGEFLAG(Young, young, PF_ANY)
SETPAGEFLAG(Young, young, PF_ANY)
TESTCLEARFLAG(Young, young, PF_ANY)
PAGEFLAG(Idle, idle, PF_ANY)
#endif

/*
 * PageReported() is used to track reported free pages within the Buddy
 * allocator. We can use the non-atomic version of the test and set
 * operations as both should be shielded with the zone lock to prevent
 * any possible races on the setting or clearing of the bit.
 */
__PAGEFLAG(Reported, reported, PF_NO_COMPOUND)

/*
 * On an anonymous page mapped into a user virtual memory area,
 * page->mapping points to its anon_vma, not to a struct address_space;
 * with the PAGE_MAPPING_ANON bit set to distinguish it.  See rmap.h.
 *
 * On an anonymous page in a VM_MERGEABLE area, if CONFIG_KSM is enabled,
 * the PAGE_MAPPING_MOVABLE bit may be set along with the PAGE_MAPPING_ANON
 * bit; and then page->mapping points, not to an anon_vma, but to a private
 * structure which KSM associates with that merged page.  See ksm.h.
 *
 * PAGE_MAPPING_KSM without PAGE_MAPPING_ANON is used for non-lru movable
 * page and then page->mapping points a struct address_space.
 *
 * Please note that, confusingly, "page_mapping" refers to the inode
 * address_space which maps the page from disk; whereas "page_mapped"
 * refers to user virtual address space into which the page is mapped.
 */
#define PAGE_MAPPING_ANON       0x1
#define PAGE_MAPPING_MOVABLE    0x2
#define PAGE_MAPPING_KSM        (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)
#define PAGE_MAPPING_FLAGS      (PAGE_MAPPING_ANON | PAGE_MAPPING_MOVABLE)

static __always_inline int PageMappingFlags(struct page *page)
{
        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) != 0;
}

static __always_inline int PageAnon(struct page *page)
{
        page = compound_head(page);
        return ((unsigned long)page->mapping & PAGE_MAPPING_ANON) != 0;
}

static __always_inline int __PageMovable(struct page *page)
{
        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
                                PAGE_MAPPING_MOVABLE;
}

#ifdef CONFIG_KSM
/*
 * A KSM page is one of those write-protected "shared pages" or "merged pages"
 * which KSM maps into multiple mms, wherever identical anonymous page content
 * is found in VM_MERGEABLE vmas.  It's a PageAnon page, pointing not to any
 * anon_vma, but to that page's node of the stable tree.
 */
static __always_inline int PageKsm(struct page *page)
{
        page = compound_head(page);
        return ((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) ==
                                PAGE_MAPPING_KSM;
}
#else
TESTPAGEFLAG_FALSE(Ksm)
#endif

u64 stable_page_flags(struct page *page);

static inline int PageUptodate(struct page *page)
{
        int ret;
        page = compound_head(page);
        ret = test_bit(PG_uptodate, &(page)->flags);
        /*
         * Must ensure that the data we read out of the page is loaded
         * _after_ we've loaded page->flags to check for PageUptodate.
         * We can skip the barrier if the page is not uptodate, because
         * we wouldn't be reading anything from it.
         *
         * See SetPageUptodate() for the other side of the story.
         */
        if (ret)
                smp_rmb();

        return ret;
}

static __always_inline void __SetPageUptodate(struct page *page)
{
        VM_BUG_ON_PAGE(PageTail(page), page);
        smp_wmb();
        __set_bit(PG_uptodate, &page->flags);
}

static __always_inline void SetPageUptodate(struct page *page)
{
        VM_BUG_ON_PAGE(PageTail(page), page);
        /*
         * Memory barrier must be issued before setting the PG_uptodate bit,
         * so that all previous stores issued in order to bring the page
         * uptodate are actually visible before PageUptodate becomes true.
         */
        smp_wmb();
        set_bit(PG_uptodate, &page->flags);
}

CLEARPAGEFLAG(Uptodate, uptodate, PF_NO_TAIL)

int test_clear_page_writeback(struct page *page);
int __test_set_page_writeback(struct page *page, bool keep_write);

#define test_set_page_writeback(page)                   \
        __test_set_page_writeback(page, false)
#define test_set_page_writeback_keepwrite(page) \
        __test_set_page_writeback(page, true)

static inline void set_page_writeback(struct page *page)
{
        test_set_page_writeback(page);
}

static inline void set_page_writeback_keepwrite(struct page *page)
{
        test_set_page_writeback_keepwrite(page);
}

__PAGEFLAG(Head, head, PF_ANY) CLEARPAGEFLAG(Head, head, PF_ANY)

static __always_inline void set_compound_head(struct page *page, struct page *head)
{
        WRITE_ONCE(page->compound_head, (unsigned long)head + 1);
}

static __always_inline void clear_compound_head(struct page *page)
{
        WRITE_ONCE(page->compound_head, 0);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static inline void ClearPageCompound(struct page *page)
{
        BUG_ON(!PageHead(page));
        ClearPageHead(page);
}
#endif

#define PG_head_mask ((1UL << PG_head))

#ifdef CONFIG_HUGETLB_PAGE
int PageHuge(struct page *page);
int PageHeadHuge(struct page *page);
#else
TESTPAGEFLAG_FALSE(Huge)
TESTPAGEFLAG_FALSE(HeadHuge)
#endif


#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/*
 * PageHuge() only returns true for hugetlbfs pages, but not for
 * normal or transparent huge pages.
 *
 * PageTransHuge() returns true for both transparent huge and
 * hugetlbfs pages, but not normal pages. PageTransHuge() can only be
 * called only in the core VM paths where hugetlbfs pages can't exist.
 */
static inline int PageTransHuge(struct page *page)
{
        VM_BUG_ON_PAGE(PageTail(page), page);
        return PageHead(page);
}

/*
 * PageTransCompound returns true for both transparent huge pages
 * and hugetlbfs pages, so it should only be called when it's known
 * that hugetlbfs pages aren't involved.
 */
static inline int PageTransCompound(struct page *page)
{
        return PageCompound(page);
}

/*
 * PageTransCompoundMap is the same as PageTransCompound, but it also
 * guarantees the primary MMU has the entire compound page mapped
 * through pmd_trans_huge, which in turn guarantees the secondary MMUs
 * can also map the entire compound page. This allows the secondary
 * MMUs to call get_user_pages() only once for each compound page and
 * to immediately map the entire compound page with a single secondary
 * MMU fault. If there will be a pmd split later, the secondary MMUs
 * will get an update through the MMU notifier invalidation through
 * split_huge_pmd().
 *
 * Unlike PageTransCompound, this is safe to be called only while
 * split_huge_pmd() cannot run from under us, like if protected by the
 * MMU notifier, otherwise it may result in page->_mapcount check false
 * positives.
 *
 * We have to treat page cache THP differently since every subpage of it
 * would get _mapcount inc'ed once it is PMD mapped.  But, it may be PTE
 * mapped in the current process so comparing subpage's _mapcount to
 * compound_mapcount to filter out PTE mapped case.
 */
static inline int PageTransCompoundMap(struct page *page)
{
        struct page *head;

        if (!PageTransCompound(page))
                return 0;

        if (PageAnon(page))
                return atomic_read(&page->_mapcount) < 0;

        head = compound_head(page);
        /* File THP is PMD mapped and not PTE mapped */
        return atomic_read(&page->_mapcount) ==
               atomic_read(compound_mapcount_ptr(head));
}

/*
 * PageTransTail returns true for both transparent huge pages
 * and hugetlbfs pages, so it should only be called when it's known
 * that hugetlbfs pages aren't involved.
 */
static inline int PageTransTail(struct page *page)
{
        return PageTail(page);
}

/*
 * PageDoubleMap indicates that the compound page is mapped with PTEs as well
 * as PMDs.
 *
 * This is required for optimization of rmap operations for THP: we can postpone
 * per small page mapcount accounting (and its overhead from atomic operations)
 * until the first PMD split.
 *
 * For the page PageDoubleMap means ->_mapcount in all sub-pages is offset up
 * by one. This reference will go away with last compound_mapcount.
 *
 * See also __split_huge_pmd_locked() and page_remove_anon_compound_rmap().
 */
static inline int PageDoubleMap(struct page *page)
{
        return PageHead(page) && test_bit(PG_double_map, &page[1].flags);
}

static inline void SetPageDoubleMap(struct page *page)
{
        VM_BUG_ON_PAGE(!PageHead(page), page);
        set_bit(PG_double_map, &page[1].flags);
}

static inline void ClearPageDoubleMap(struct page *page)
{
        VM_BUG_ON_PAGE(!PageHead(page), page);
        clear_bit(PG_double_map, &page[1].flags);
}
static inline int TestSetPageDoubleMap(struct page *page)
{
        VM_BUG_ON_PAGE(!PageHead(page), page);
        return test_and_set_bit(PG_double_map, &page[1].flags);
}

static inline int TestClearPageDoubleMap(struct page *page)
{
        VM_BUG_ON_PAGE(!PageHead(page), page);
        return test_and_clear_bit(PG_double_map, &page[1].flags);
}

#else
TESTPAGEFLAG_FALSE(TransHuge)
TESTPAGEFLAG_FALSE(TransCompound)
TESTPAGEFLAG_FALSE(TransCompoundMap)
TESTPAGEFLAG_FALSE(TransTail)
PAGEFLAG_FALSE(DoubleMap)
        TESTSETFLAG_FALSE(DoubleMap)
        TESTCLEARFLAG_FALSE(DoubleMap)
#endif

/*
 * For pages that are never mapped to userspace (and aren't PageSlab),
 * page_type may be used.  Because it is initialised to -1, we invert the
 * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and
 * __ClearPageFoo *sets* the bit used for PageFoo.  We reserve a few high and
 * low bits so that an underflow or overflow of page_mapcount() won't be
 * mistaken for a page type value.
 */

#define PAGE_TYPE_BASE  0xf0000000
/* Reserve              0x0000007f to catch underflows of page_mapcount */
#define PAGE_MAPCOUNT_RESERVE   -128
#define PG_buddy        0x00000080
#define PG_offline      0x00000100
#define PG_table        0x00000200
#define PG_guard        0x00000400

#define PageType(page, flag)                                            \
        ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)

static inline int page_has_type(struct page *page)
{
        return (int)page->page_type < PAGE_MAPCOUNT_RESERVE;
}

#define PAGE_TYPE_OPS(uname, lname)                                     \
static __always_inline int Page##uname(struct page *page)               \
{                                                                       \
        return PageType(page, PG_##lname);                              \
}                                                                       \
static __always_inline void __SetPage##uname(struct page *page)         \
{                                                                       \
        VM_BUG_ON_PAGE(!PageType(page, 0), page);                       \
        page->page_type &= ~PG_##lname;                                 \
}                                                                       \
static __always_inline void __ClearPage##uname(struct page *page)       \
{                                                                       \
        VM_BUG_ON_PAGE(!Page##uname(page), page);                       \
        page->page_type |= PG_##lname;                                  \
}

/*
 * PageBuddy() indicates that the page is free and in the buddy system
 * (see mm/page_alloc.c).
 */
PAGE_TYPE_OPS(Buddy, buddy)

/*
 * PageOffline() indicates that the page is logically offline although the
 * containing section is online. (e.g. inflated in a balloon driver or
 * not onlined when onlining the section).
 * The content of these pages is effectively stale. Such pages should not
 * be touched (read/write/dump/save) except by their owner.
 *
 * If a driver wants to allow to offline unmovable PageOffline() pages without
 * putting them back to the buddy, it can do so via the memory notifier by
 * decrementing the reference count in MEM_GOING_OFFLINE and incrementing the
 * reference count in MEM_CANCEL_OFFLINE. When offlining, the PageOffline()
 * pages (now with a reference count of zero) are treated like free pages,
 * allowing the containing memory block to get offlined. A driver that
 * relies on this feature is aware that re-onlining the memory block will
 * require to re-set the pages PageOffline() and not giving them to the
 * buddy via online_page_callback_t.
 */
PAGE_TYPE_OPS(Offline, offline)

/*
 * Marks pages in use as page tables.
 */
PAGE_TYPE_OPS(Table, table)

/*
 * Marks guardpages used with debug_pagealloc.
 */
PAGE_TYPE_OPS(Guard, guard)

extern bool is_free_buddy_page(struct page *page);

__PAGEFLAG(Isolated, isolated, PF_ANY);

/*
 * If network-based swap is enabled, sl*b must keep track of whether pages
 * were allocated from pfmemalloc reserves.
 */
static inline int PageSlabPfmemalloc(struct page *page)
{
        VM_BUG_ON_PAGE(!PageSlab(page), page);
        return PageActive(page);
}

static inline void SetPageSlabPfmemalloc(struct page *page)
{
        VM_BUG_ON_PAGE(!PageSlab(page), page);
        SetPageActive(page);
}

static inline void __ClearPageSlabPfmemalloc(struct page *page)
{
        VM_BUG_ON_PAGE(!PageSlab(page), page);
        __ClearPageActive(page);
}

static inline void ClearPageSlabPfmemalloc(struct page *page)
{
        VM_BUG_ON_PAGE(!PageSlab(page), page);
        ClearPageActive(page);
}

#ifdef CONFIG_MMU
#define __PG_MLOCKED            (1UL << PG_mlocked)
#else
#define __PG_MLOCKED            0
#endif

/*
 * Flags checked when a page is freed.  Pages being freed should not have
 * these flags set.  It they are, there is a problem.
 */
#define PAGE_FLAGS_CHECK_AT_FREE                                \
        (1UL << PG_lru          | 1UL << PG_locked      |       \
         1UL << PG_private      | 1UL << PG_private_2   |       \
         1UL << PG_writeback    | 1UL << PG_reserved    |       \
         1UL << PG_slab         | 1UL << PG_active      |       \
         1UL << PG_unevictable  | __PG_MLOCKED)

/*
 * Flags checked when a page is prepped for return by the page allocator.
 * Pages being prepped should not have these flags set.  It they are set,
 * there has been a kernel bug or struct page corruption.
 *
 * __PG_HWPOISON is exceptional because it needs to be kept beyond page's
 * alloc-free cycle to prevent from reusing the page.
 */
#define PAGE_FLAGS_CHECK_AT_PREP        \
        (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON)

#define PAGE_FLAGS_PRIVATE                              \
        (1UL << PG_private | 1UL << PG_private_2)
/**
 * page_has_private - Determine if page has private stuff
 * @page: The page to be checked
 *
 * Determine if a page has private stuff, indicating that release routines
 * should be invoked upon it.
 */
static inline int page_has_private(struct page *page)
{
        return !!(page->flags & PAGE_FLAGS_PRIVATE);
}

#undef PF_ANY
#undef PF_HEAD
#undef PF_ONLY_HEAD
#undef PF_NO_TAIL
#undef PF_NO_COMPOUND
#endif /* !__GENERATING_BOUNDS_H */

#endif  /* PAGE_FLAGS_H */