From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
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.
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
fs/proc/page.c | 2 ++
include/linux/mm.h | 2 ++
include/linux/page-flags.h | 6 ++++++
include/uapi/linux/kernel-page-flags.h | 2 +-
tools/vm/page-types.c | 1 +
5 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/fs/proc/page.c b/fs/proc/page.c
index 1491918a33c3..792c78a49174 100644
--- 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
index 974e8f8ffe03..5c6069219425 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1819,6 +1819,7 @@ 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;
}
@@ -1826,6 +1827,7 @@ static inline bool pgtable_page_ctor(struct page *page)
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
index 8c25b28a35aa..901943e4754b 100644
--- 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
index fa139841ec18..21b9113c69da 100644
--- 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
index a8783f48f77f..cce853dca691 100644
--- 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",
--
2.17.0
