mm: mark pages in use for page tables

Matthew Wilcox · torvalds · commit 1d40a5ea01d5 · 2018-06-07T17:34:37.000-07:00
Define a new PageTable bit in the page_type and use it to mark pages in use as page tables. This can be helpful when debugging crashdumps or analysing memory fragmentation. Add a KPF flag to report these pages to userspace and update page-types.c to interpret that flag. Note that only pages currently accounted as NR_PAGETABLES are tracked as PageTable; this does not include pgd/p4d/pud/pmd pages. Those will be the subject of a later patch. Link: http://lkml.kernel.org/r/20180518194519.3820-4-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Jérôme Glisse <jglisse@redhat.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/page.c b/fs/proc/page.c
@@ -154,6 +154,8 @@ u64 stable_page_flags(struct page *page)
 
 	if (PageBalloon(page))
 		u |= 1 << KPF_BALLOON;
+	if (PageTable(page))
+		u |= 1 << KPF_PGTABLE;
 
 	if (page_is_idle(page))
 		u |= 1 << KPF_IDLE;
diff --git a/include/linux/mm.h b/include/linux/mm.h
@@ -1851,13 +1851,15 @@ static inline bool pgtable_page_ctor(struct page *page)
 {
 	if (!ptlock_init(page))
 		return false;
+	__SetPageTable(page);
 	inc_zone_page_state(page, NR_PAGETABLE);
 	return true;
 }
 
 static inline void pgtable_page_dtor(struct page *page)
 {
 	pte_lock_deinit(page);
+	__ClearPageTable(page);
 	dec_zone_page_state(page, NR_PAGETABLE);
 }
 
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
@@ -655,6 +655,7 @@ PAGEFLAG_FALSE(DoubleMap)
 #define PG_buddy	0x00000080
 #define PG_balloon	0x00000100
 #define PG_kmemcg	0x00000200
+#define PG_table	0x00000400
 
 #define PageType(page, flag)						\
 	((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE)
@@ -693,6 +694,11 @@ PAGE_TYPE_OPS(Balloon, balloon)
  */
 PAGE_TYPE_OPS(Kmemcg, kmemcg)
 
+/*
+ * Marks pages in use as page tables.
+ */
+PAGE_TYPE_OPS(Table, table)
+
 extern bool is_free_buddy_page(struct page *page);
 
 __PAGEFLAG(Isolated, isolated, PF_ANY);
diff --git a/include/uapi/linux/kernel-page-flags.h b/include/uapi/linux/kernel-page-flags.h
@@ -35,6 +35,6 @@
 #define KPF_BALLOON		23
 #define KPF_ZERO_PAGE		24
 #define KPF_IDLE		25
-
+#define KPF_PGTABLE		26
 
 #endif /* _UAPILINUX_KERNEL_PAGE_FLAGS_H */
diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c
@@ -131,6 +131,7 @@ static const char * const page_flag_names[] = {
 	[KPF_KSM]		= "x:ksm",
 	[KPF_THP]		= "t:thp",
 	[KPF_BALLOON]		= "o:balloon",
+	[KPF_PGTABLE]		= "g:pgtable",
 	[KPF_ZERO_PAGE]		= "z:zero_page",
 	[KPF_IDLE]              = "i:idle_page",
 

Original file line number	Diff line number	Diff line change
`@@ -1851,13 +1851,15 @@ static inline bool pgtable_page_ctor(struct page *page)`
`1851`	`1851`	`{`
`1852`	`1852`	`if (!ptlock_init(page))`
`1853`	`1853`	`return false;`
	`1854`	`+ __SetPageTable(page);`
`1854`	`1855`	`inc_zone_page_state(page, NR_PAGETABLE);`
`1855`	`1856`	`return true;`
`1856`	`1857`	`}`
`1857`	`1858`
`1858`	`1859`	`static inline void pgtable_page_dtor(struct page *page)`
`1859`	`1860`	`{`
`1860`	`1861`	`pte_lock_deinit(page);`
	`1862`	`+ __ClearPageTable(page);`
`1861`	`1863`	`dec_zone_page_state(page, NR_PAGETABLE);`
`1862`	`1864`	`}`
`1863`	`1865`