diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 74bee8c..1bf83c8 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -17,8 +17,37 @@
 /*
  * Various page->flags bits:
  *
- * PG_reserved is set for special pages, which can never be swapped out. Some
- * of them might not even exist...
+ * PG_reserved is set for special pages. The "struct page" of such a page
+ * should in general not be touched (e.g. set dirty) except by its owner.
+ * Pages marked as PG_reserved include:
+ * - Pages part of the kernel image (including vDSO) and similar (e.g. BIOS,
+ *   initrd, HW tables)
+ * - Pages reserved or allocated early during boot (before the page allocator
+ *   was initialized). This includes (depending on the architecture) the
+ *   initial vmemmap, initial page tables, crashkernel, elfcorehdr, and much
+ *   much more. Once (if ever) freed, PG_reserved is cleared and they will
+ *   be given to the page allocator.
+ * - Pages falling into physical memory gaps - not IORESOURCE_SYSRAM. Trying
+ *   to read/write these pages might end badly. Don't touch!
+ * - The zero page(s)
+ * - Pages not added to the page allocator when onlining a section because
+ *   they were excluded via the online_page_callback() or because they are
+ *   PG_hwpoison.
+ * - Pages allocated in the context of kexec/kdump (loaded kernel image,
+ *   control pages, vmcoreinfo)
+ * - MMIO/DMA pages. Some architectures don't allow to ioremap pages that are
+ *   not marked PG_reserved (as they might be in use by somebody else who does
+ *   not respect the caching strategy).
+ * - Pages part of an offline section (struct pages of offline sections should
+ *   not be trusted as they will be initialized when first onlined).
+ * - MCA pages on ia64
+ * - Pages holding CPU notes for POWER Firmware Assisted Dump
+ * - Device memory (e.g. PMEM, DAX, HMM)
+ * Some PG_reserved pages will be excluded from the hibernation image.
+ * PG_reserved does in general not hinder anybody from dumping or swapping
+ * and is no longer required for remap_pfn_range(). ioremap might require it.
+ * Consequently, PG_reserved for a page mapped into user space can indicate
+ * the zero page, the vDSO, MMIO pages or device memory.
  *
  * 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
@@ -69,13 +98,14 @@
  */
 enum pageflags {
 	PG_locked,		/* Page is locked. Don't touch. */
-	PG_error,
 	PG_referenced,
 	PG_uptodate,
 	PG_dirty,
 	PG_lru,
 	PG_active,
+	PG_workingset,
 	PG_waiters,		/* Page has waiters, check its waitqueue. Must be bit #7 and in the same byte as "PG_locked" */
+	PG_error,
 	PG_slab,
 	PG_owner_priv_1,	/* Owner use. If pagecache, fs may use*/
 	PG_arch_1,
@@ -122,6 +152,8 @@
 	PG_savepinned = PG_dirty,
 	/* Has a grant mapping of another (foreign) domain's page. */
 	PG_foreign = PG_owner_priv_1,
+	/* Remapped by swiotlb-xen. */
+	PG_xen_remapped = PG_owner_priv_1,
 
 	/* SLOB */
 	PG_slob_free = PG_private,
@@ -162,6 +194,14 @@
 	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
  *
@@ -280,6 +320,8 @@
 PAGEFLAG(LRU, lru, PF_HEAD) __CLEARPAGEFLAG(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 */
@@ -289,9 +331,12 @@
 	TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
 PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
 PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
+PAGEFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND)
+	TESTCLEARFLAG(XenRemapped, xen_remapped, 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)
@@ -577,12 +622,28 @@
  *
  * 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 < 0 false
+ * 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)
 {
-	return PageTransCompound(page) && atomic_read(&page->_mapcount) < 0;
+	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));
 }
 
 /*
@@ -657,14 +718,21 @@
 
 #define PAGE_TYPE_BASE	0xf0000000
 /* Reserve		0x0000007f to catch underflows of page_mapcount */
+#define PAGE_MAPCOUNT_RESERVE	-128
 #define PG_buddy	0x00000080
-#define PG_balloon	0x00000100
+#define PG_offline	0x00000100
 #define PG_kmemcg	0x00000200
 #define PG_table	0x00000400
+#define PG_guard	0x00000800
 
 #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)		\
 {									\
@@ -688,10 +756,13 @@
 PAGE_TYPE_OPS(Buddy, buddy)
 
 /*
- * PageBalloon() is true for pages that are on the balloon page list
- * (see mm/balloon_compaction.c).
+ * 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.
  */
-PAGE_TYPE_OPS(Balloon, balloon)
+PAGE_TYPE_OPS(Offline, offline)
 
 /*
  * If kmemcg is enabled, the buddy allocator will set PageKmemcg() on
@@ -704,6 +775,11 @@
  */
 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);