[RFC PATCH 5/8] mm: add reserved THP vma flag

[Qi Zheng]

From: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>

Introduce the VM_RESERVED_THP VMA flag to mark Virtual Memory Areas (VMAs)
that have the reserved THP policy enabled.

Also, add the "rt" (reserved THP) flag indicator to the output of
/proc/<pid>/smaps to facilitate monitoring and debugging the status of
the corresponding VMAs from userspace.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
 fs/proc/task_mmu.c              | 3 +++
 include/linux/mm.h              | 7 +++++++
 tools/testing/vma/include/dup.h | 1 +
 3 files changed, 11 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index d32408f7cd5ed..65c4b2a61aeac 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1245,6 +1245,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 #endif
 #ifdef CONFIG_64BIT
 		[ilog2(VM_SEALED)] = "sl",
+#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+		[ilog2(VM_RESERVED_THP)] = "rt",
 #endif
 	};
 	size_t i;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 485df9c2dbddb..278cf4bfd4ec5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -353,6 +353,7 @@ enum {
 #endif
 	DECLARE_VMA_BIT(UFFD_MINOR, 41),
 	DECLARE_VMA_BIT(SEALED, 42),
+	DECLARE_VMA_BIT(RESERVED_THP, 43),
 	/* Flags that reuse flags above. */
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT0, HIGH_ARCH_0),
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT1, HIGH_ARCH_1),
@@ -526,6 +527,12 @@ enum {
 #define VMA_DROPPABLE		EMPTY_VMA_FLAGS
 #endif
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#define VM_RESERVED_THP		INIT_VM_FLAG(RESERVED_THP)
+#else
+#define VM_RESERVED_THP		VM_NONE
+#endif
+
 /* Bits set in the VMA until the stack is in its final location */
 #define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ | VM_STACK_EARLY)
 
diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index cf73bcd9bb9d5..022b7a56b6a9f 100644
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h
@@ -160,6 +160,7 @@ enum {
 #endif
 	DECLARE_VMA_BIT(UFFD_MINOR, 41),
 	DECLARE_VMA_BIT(SEALED, 42),
+	DECLARE_VMA_BIT(RESERVED_THP, 43),
 	/* Flags that reuse flags above. */
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT0, HIGH_ARCH_0),
 	DECLARE_VMA_BIT_ALIAS(PKEY_BIT1, HIGH_ARCH_1),
-- 
2.54.0