[PATCH v2 5/9] mm/mshare: Add vm flag for shared PTE

Khalid Aziz
2022-06-29T22:56:43Z

Add a bit to vm_flags to indicate a vma shares PTEs with others. Add
a function to determine if a vma shares PTE by checking this flag.
This is to be used to find the shared page table entries on page fault
for vmas sharing PTE.

Signed-off-by: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
include/linux/mm.h | 8 ++++++++
include/trace/events/mmflags.h | 3 ++-
mm/internal.h | 5 +++++
3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index bc8f326be0ce..0ddc3057f73b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -310,11 +310,13 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit architectures */
+#define VM_HIGH_ARCH_BIT_5 37 /* bit only usable on 64-bit architectures */
#define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
#define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
#define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
#define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
+#define VM_HIGH_ARCH_5 BIT(VM_HIGH_ARCH_BIT_5)
#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */

#ifdef CONFIG_ARCH_HAS_PKEYS
@@ -356,6 +358,12 @@ extern unsigned int kobjsize(const void *objp);
# define VM_MTE_ALLOWED VM_NONE
#endif

+#ifdef CONFIG_ARCH_USES_HIGH_VMA_FLAGS
+#define VM_SHARED_PT VM_HIGH_ARCH_5
+#else
+#define VM_SHARED_PT 0
+#endif
+
#ifndef VM_GROWSUP
# define VM_GROWSUP VM_NONE
#endif
diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h
index e87cb2b80ed3..30e56cbac99b 100644
--- a/include/trace/events/mmflags.h
+++ b/include/trace/events/mmflags.h
@@ -194,7 +194,8 @@ IF_HAVE_VM_SOFTDIRTY(VM_SOFTDIRTY, "softdirty" ) \
{VM_MIXEDMAP, "mixedmap" }, \
{VM_HUGEPAGE, "hugepage" }, \
{VM_NOHUGEPAGE, "nohugepage" }, \
- {VM_MERGEABLE, "mergeable" } \
+ {VM_MERGEABLE, "mergeable" }, \
+ {VM_SHARED_PT, "sharedpt" } \

#define show_vma_flags(flags) \
(flags) ? __print_flags(flags, "|", \
diff --git a/mm/internal.h b/mm/internal.h
index c0f8fbe0445b..3f2790aea918 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -861,4 +861,9 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags);

DECLARE_PER_CPU(struct per_cpu_nodestat, boot_nodestats);

+static inline bool vma_is_shared(const struct vm_area_struct *vma)
+{
+ return vma->vm_flags & VM_SHARED_PT;
+}
+
#endif /* __MM_INTERNAL_H */
--
2.32.0