[PATCH v2 01/13] mm: introduce vma_flags_can_grow() and vma_can_grow()

[Lorenzo Stoakes <ljs@kernel.org>]

These test whether the VMA has stack semantics, i.e. is able to grow
upwards or downwards depending on the architecture.

In order to account for arches which do not support upward-growing stacks,
introduce VMA_GROWSUP whose definition depends on the architecture
supporting it, and use vma_flags_test_single_mask() in vma_flags_can_grow()
to account for this.

No functional change intended.

Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
---
 include/linux/mm.h | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 32bb723ffbb9..7a7f559b3df0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -474,6 +474,7 @@ enum {
 #define VM_SAO		INIT_VM_FLAG(SAO)
 #elif defined(CONFIG_PARISC)
 #define VM_GROWSUP	INIT_VM_FLAG(GROWSUP)
+#define VMA_GROWSUP	mk_vma_flags(VMA_GROWSUP_BIT)
 #elif defined(CONFIG_SPARC64)
 #define VM_SPARC_ADI	INIT_VM_FLAG(SPARC_ADI)
 #define VM_ARCH_CLEAR	INIT_VM_FLAG(ARCH_CLEAR)
@@ -485,6 +486,7 @@ enum {
 #endif
 #ifndef VM_GROWSUP
 #define VM_GROWSUP	VM_NONE
+#define VMA_GROWSUP	EMPTY_VMA_FLAGS
 #endif
 #ifdef CONFIG_ARM64_MTE
 #define VM_MTE		INIT_VM_FLAG(MTE)
@@ -1578,11 +1580,24 @@ static inline bool vma_is_initial_stack(const struct vm_area_struct *vma)
 		vma->vm_end >= vma->vm_mm->start_stack;
 }
 
-static inline bool vma_is_temporary_stack(const struct vm_area_struct *vma)
+static inline bool vma_flags_can_grow(const vma_flags_t *flags)
 {
-	int maybe_stack = vma->vm_flags & (VM_GROWSDOWN | VM_GROWSUP);
+	if (vma_flags_test_single_mask(flags, VMA_GROWSUP))
+		return true;
+	if (vma_flags_test(flags, VMA_GROWSDOWN_BIT))
+		return true;
+
+	return false;
+}
 
-	if (!maybe_stack)
+static inline bool vma_can_grow(const struct vm_area_struct *vma)
+{
+	return vma_flags_can_grow(&vma->flags);
+}
+
+static inline bool vma_is_temporary_stack(const struct vm_area_struct *vma)
+{
+	if (!vma_can_grow(vma))
 		return false;
 
 	if ((vma->vm_flags & VM_STACK_INCOMPLETE_SETUP) ==

-- 
2.55.0