[v7,1/1] mm: report per-page metadata information

diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
index 49ef12df631b..d5901d04e082 100644
--- a/Documentation/filesystems/proc.rst
+++ b/Documentation/filesystems/proc.rst
@@ -993,6 +993,7 @@  Example output. You may not have all of these fields.
     AnonPages:       4654780 kB
     Mapped:           266244 kB
     Shmem:              9976 kB
+    PageMetadata:     513419 kB
     KReclaimable:     517708 kB
     Slab:             660044 kB
     SReclaimable:     517708 kB
@@ -1095,6 +1096,8 @@  Mapped
               files which have been mmapped, such as libraries
 Shmem
               Total memory used by shared memory (shmem) and tmpfs
+PageMetadata
+              Memory used for per-page metadata
 KReclaimable
               Kernel allocations that the kernel will attempt to reclaim
               under memory pressure. Includes SReclaimable (below), and other
diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 45af9a989d40..e0bde16717fd 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -39,6 +39,7 @@  static int meminfo_proc_show(struct seq_file *m, void *v)
 	long available;
 	unsigned long pages[NR_LRU_LISTS];
 	unsigned long sreclaimable, sunreclaim;
+	unsigned long nr_page_metadata;
 	int lru;
 
 	si_meminfo(&i);
@@ -57,6 +58,8 @@  static int meminfo_proc_show(struct seq_file *m, void *v)
 	sreclaimable = global_node_page_state_pages(NR_SLAB_RECLAIMABLE_B);
 	sunreclaim = global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B);
 
+	nr_page_metadata = global_node_page_state_pages(NR_PAGE_METADATA);
+
 	show_val_kb(m, "MemTotal:       ", i.totalram);
 	show_val_kb(m, "MemFree:        ", i.freeram);
 	show_val_kb(m, "MemAvailable:   ", available);
@@ -104,6 +107,7 @@  static int meminfo_proc_show(struct seq_file *m, void *v)
 	show_val_kb(m, "Mapped:         ",
 		    global_node_page_state(NR_FILE_MAPPED));
 	show_val_kb(m, "Shmem:          ", i.sharedram);
+	show_val_kb(m, "PageMetadata:   ", nr_page_metadata);
 	show_val_kb(m, "KReclaimable:   ", sreclaimable +
 		    global_node_page_state(NR_KERNEL_MISC_RECLAIMABLE));
 	show_val_kb(m, "Slab:           ", sreclaimable + sunreclaim);
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 3c25226beeed..ef176152be7c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -207,6 +207,10 @@  enum node_stat_item {
 	PGPROMOTE_SUCCESS,	/* promote successfully */
 	PGPROMOTE_CANDIDATE,	/* candidate pages to promote */
 #endif
+	NR_PAGE_METADATA,	/* Page metadata size (struct page and page_ext)
+				 * in pages
+				 */
+	NR_PAGE_METADATA_BOOT,	/* NR_PAGE_METADATA for bootmem */
 	NR_VM_NODE_STAT_ITEMS
 };
 
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index fed855bae6d8..af096a881f03 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -656,4 +656,8 @@  static inline void lruvec_stat_sub_folio(struct folio *folio,
 {
 	lruvec_stat_mod_folio(folio, idx, -folio_nr_pages(folio));
 }
+
+void __init mod_node_early_perpage_metadata(int nid, long delta);
+void __init store_early_perpage_metadata(void);
+
 #endif /* _LINUX_VMSTAT_H */
diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
index 87818ee7f01d..5b10d8d2b471 100644
--- a/mm/hugetlb_vmemmap.c
+++ b/mm/hugetlb_vmemmap.c
@@ -230,10 +230,14 @@  static int vmemmap_remap_range(unsigned long start, unsigned long end,
  */
 static inline void free_vmemmap_page(struct page *page)
 {
-	if (PageReserved(page))
+	if (PageReserved(page)) {
 		free_bootmem_page(page);
-	else
+		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA_BOOT,
+				    -1);
+	} else {
 		__free_page(page);
+		mod_node_page_state(page_pgdat(page), NR_PAGE_METADATA, -1);
+	}
 }
 
 /* Free a list of the vmemmap pages */
@@ -389,6 +393,7 @@  static int vmemmap_remap_free(unsigned long start, unsigned long end,
 		copy_page(page_to_virt(walk.reuse_page),
 			  (void *)walk.reuse_addr);
 		list_add(&walk.reuse_page->lru, vmemmap_pages);
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, 1);
 	}
 
 	/*
@@ -437,14 +442,20 @@  static int alloc_vmemmap_page_list(unsigned long start, unsigned long end,
 	unsigned long nr_pages = (end - start) >> PAGE_SHIFT;
 	int nid = page_to_nid((struct page *)start);
 	struct page *page, *next;
+	int i;
 
-	while (nr_pages--) {
+	for (i = 0; i < nr_pages; i++) {
 		page = alloc_pages_node(nid, gfp_mask, 0);
-		if (!page)
+		if (!page) {
+			mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+					    i);
 			goto out;
+		}
 		list_add(&page->lru, list);
 	}
 
+	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA, nr_pages);
+
 	return 0;
 out:
 	list_for_each_entry_safe(page, next, list, lru)
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 077bfe393b5e..38f8e1f454a0 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -26,6 +26,7 @@ 
 #include <linux/pgtable.h>
 #include <linux/swap.h>
 #include <linux/cma.h>
+#include <linux/vmstat.h>
 #include "internal.h"
 #include "slab.h"
 #include "shuffle.h"
@@ -1656,6 +1657,8 @@  static void __init alloc_node_mem_map(struct pglist_data *pgdat)
 			panic("Failed to allocate %ld bytes for node %d memory map\n",
 			      size, pgdat->node_id);
 		pgdat->node_mem_map = map + offset;
+		mod_node_early_perpage_metadata(pgdat->node_id,
+						DIV_ROUND_UP(size, PAGE_SIZE));
 	}
 	pr_debug("%s: node %d, pgdat %08lx, node_mem_map %08lx\n",
 				__func__, pgdat->node_id, (unsigned long)pgdat,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 733732e7e0ba..dd78017105b0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5636,6 +5636,7 @@  void __init setup_per_cpu_pageset(void)
 	for_each_online_pgdat(pgdat)
 		pgdat->per_cpu_nodestats =
 			alloc_percpu(struct per_cpu_nodestat);
+	store_early_perpage_metadata();
 }
 
 __meminit void zone_pcp_init(struct zone *zone)
diff --git a/mm/page_ext.c b/mm/page_ext.c
index 4548fcc66d74..4ca9f298f34e 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -201,6 +201,8 @@  static int __init alloc_node_page_ext(int nid)
 		return -ENOMEM;
 	NODE_DATA(nid)->node_page_ext = base;
 	total_usage += table_size;
+	mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+			    DIV_ROUND_UP(table_size, PAGE_SIZE));
 	return 0;
 }
 
@@ -255,12 +257,15 @@  static void *__meminit alloc_page_ext(size_t size, int nid)
 	void *addr = NULL;
 
 	addr = alloc_pages_exact_nid(nid, size, flags);
-	if (addr) {
+	if (addr)
 		kmemleak_alloc(addr, size, 1, flags);
-		return addr;
-	}
+	else
+		addr = vzalloc_node(size, nid);
 
-	addr = vzalloc_node(size, nid);
+	if (addr) {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+				    DIV_ROUND_UP(size, PAGE_SIZE));
+	}
 
 	return addr;
 }
@@ -303,18 +308,27 @@  static int __meminit init_section_page_ext(unsigned long pfn, int nid)
 
 static void free_page_ext(void *addr)
 {
+	size_t table_size;
+	struct page *page;
+	struct pglist_data *pgdat;
+
+	table_size = page_ext_size * PAGES_PER_SECTION;
+
 	if (is_vmalloc_addr(addr)) {
+		page = vmalloc_to_page(addr);
+		pgdat = page_pgdat(page);
 		vfree(addr);
 	} else {
-		struct page *page = virt_to_page(addr);
-		size_t table_size;
-
-		table_size = page_ext_size * PAGES_PER_SECTION;
-
+		page = virt_to_page(addr);
+		pgdat = page_pgdat(page);
 		BUG_ON(PageReserved(page));
 		kmemleak_free(addr);
 		free_pages_exact(addr, table_size);
 	}
+
+	mod_node_page_state(pgdat, NR_PAGE_METADATA,
+			    -1L * (DIV_ROUND_UP(table_size, PAGE_SIZE)));
+
 }
 
 static void __free_page_ext(unsigned long pfn)
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index a2cbe44c48e1..054b49539843 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -469,5 +469,13 @@  struct page * __meminit __populate_section_memmap(unsigned long pfn,
 	if (r < 0)
 		return NULL;
 
+	if (system_state == SYSTEM_BOOTING) {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+				    DIV_ROUND_UP(end - start, PAGE_SIZE));
+	} else {
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA,
+				    DIV_ROUND_UP(end - start, PAGE_SIZE));
+	}
+
 	return pfn_to_page(pfn);
 }
diff --git a/mm/sparse.c b/mm/sparse.c
index 77d91e565045..0c100ae1cf8b 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -14,7 +14,7 @@ 
 #include <linux/swap.h>
 #include <linux/swapops.h>
 #include <linux/bootmem_info.h>
-
+#include <linux/vmstat.h>
 #include "internal.h"
 #include <asm/dma.h>
 
@@ -465,6 +465,9 @@  static void __init sparse_buffer_init(unsigned long size, int nid)
 	 */
 	sparsemap_buf = memmap_alloc(size, section_map_size(), addr, nid, true);
 	sparsemap_buf_end = sparsemap_buf + size;
+#ifndef CONFIG_SPARSEMEM_VMEMMAP
+	mod_node_early_perpage_metadata(nid, DIV_ROUND_UP(size, PAGE_SIZE));
+#endif
 }
 
 static void __init sparse_buffer_fini(void)
@@ -641,6 +644,8 @@  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
 	unsigned long start = (unsigned long) pfn_to_page(pfn);
 	unsigned long end = start + nr_pages * sizeof(struct page);
 
+	mod_node_page_state(page_pgdat(pfn_to_page(pfn)), NR_PAGE_METADATA,
+			    -1L * (DIV_ROUND_UP(end - start, PAGE_SIZE)));
 	vmemmap_free(start, end, altmap);
 }
 static void free_map_bootmem(struct page *memmap)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 359460deb377..23e88d8c21b7 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1249,7 +1249,8 @@  const char * const vmstat_text[] = {
 	"pgpromote_success",
 	"pgpromote_candidate",
 #endif
-
+	"nr_page_metadata",
+	"nr_page_metadata_boot",
 	/* enum writeback_stat_item counters */
 	"nr_dirty_threshold",
 	"nr_dirty_background_threshold",
@@ -2278,4 +2279,27 @@  static int __init extfrag_debug_init(void)
 }
 
 module_init(extfrag_debug_init);
+
 #endif
+
+/*
+ * Page metadata size (struct page and page_ext) in pages
+ */
+static unsigned long early_perpage_metadata[MAX_NUMNODES] __initdata;
+
+void __init mod_node_early_perpage_metadata(int nid, long delta)
+{
+	early_perpage_metadata[nid] += delta;
+}
+
+void __init store_early_perpage_metadata(void)
+{
+	int nid;
+	struct pglist_data *pgdat;
+
+	for_each_online_pgdat(pgdat) {
+		nid = pgdat->node_id;
+		mod_node_page_state(NODE_DATA(nid), NR_PAGE_METADATA_BOOT,
+				    early_perpage_metadata[nid]);
+	}
+}