[PATCH v4 11/25] mm/vma: introduce [vma_flags,legacy]_to_[legacy,vma_flags]() helpers

Lorenzo Stoakes (Oracle)
2026-03-20T19:39:17Z

While we are still converting VMA flags from vma_flags_t to vm_flags_t,
introduce helpers to convert between the two to allow for iterative
development without having to 'change the world' in a single commit'.

Also update VMA flags tests to reflect the change.

Finally, refresh vma_flags_overwrite_word(),
vma_flag_overwrite_word_once(), vma_flags_set_word() and
vma_flags_clear_word() in the VMA tests to reflect current kernel
implementations - this should make no functional difference, but keeps the
logic consistent between the two.

Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
---
include/linux/mm_types.h | 26 ++++++++++++++++++++++++
tools/testing/vma/include/dup.h | 36 +++++++++++++++++++++++++++++----
2 files changed, 58 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 47d64057b74c..c5ad55b8a45b 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1069,6 +1069,18 @@ static __always_inline void vma_flags_clear_all(vma_flags_t *flags)
bitmap_zero(flags->__vma_flags, NUM_VMA_FLAG_BITS);
}

+/*
+ * Helper function which converts a vma_flags_t value to a legacy vm_flags_t
+ * value. This is only valid if the input flags value can be expressed in a
+ * system word.
+ *
+ * Will be removed once the conversion to VMA flags is complete.
+ */
+static __always_inline vm_flags_t vma_flags_to_legacy(vma_flags_t flags)
+{
+ return (vm_flags_t)flags.__vma_flags[0];
+}
+
/*
* Copy value to the first system word of VMA flags, non-atomically.
*
@@ -1082,6 +1094,20 @@ static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long va
bitmap[0] = value;
}

+/*
+ * Helper function which converts a legacy vm_flags_t value to a vma_flags_t
+ * value.
+ *
+ * Will be removed once the conversion to VMA flags is complete.
+ */
+static __always_inline vma_flags_t legacy_to_vma_flags(vm_flags_t flags)
+{
+ vma_flags_t ret = EMPTY_VMA_FLAGS;
+
+ vma_flags_overwrite_word(&ret, flags);
+ return ret;
+}
+
/*
* Copy value to the first system word of VMA flags ONCE, non-atomically.
*
diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index 65f630923461..f49af21319ba 100644
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h
@@ -766,7 +766,9 @@ static inline bool mm_flags_test(int flag, const struct mm_struct *mm)
*/
static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long value)
{
- *ACCESS_PRIVATE(flags, __vma_flags) = value;
+ unsigned long *bitmap = flags->__vma_flags;
+
+ bitmap[0] = value;
}

/*
@@ -777,7 +779,7 @@ static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long va
*/
static inline void vma_flags_overwrite_word_once(vma_flags_t *flags, unsigned long value)
{
- unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
+ unsigned long *bitmap = flags->__vma_flags;

WRITE_ONCE(*bitmap, value);
}
@@ -785,7 +787,7 @@ static inline void vma_flags_overwrite_word_once(vma_flags_t *flags, unsigned lo
/* Update the first system word of VMA flags setting bits, non-atomically. */
static inline void vma_flags_set_word(vma_flags_t *flags, unsigned long value)
{
- unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
+ unsigned long *bitmap = flags->__vma_flags;

*bitmap |= value;
}
@@ -793,7 +795,7 @@ static inline void vma_flags_set_word(vma_flags_t *flags, unsigned long value)
/* Update the first system word of VMA flags clearing bits, non-atomically. */
static inline void vma_flags_clear_word(vma_flags_t *flags, unsigned long value)
{
- unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);
+ unsigned long *bitmap = flags->__vma_flags;

*bitmap &= ~value;
}
@@ -803,6 +805,32 @@ static __always_inline void vma_flags_clear_all(vma_flags_t *flags)
bitmap_zero(ACCESS_PRIVATE(flags, __vma_flags), NUM_VMA_FLAG_BITS);
}

+/*
+ * Helper function which converts a vma_flags_t value to a legacy vm_flags_t
+ * value. This is only valid if the input flags value can be expressed in a
+ * system word.
+ *
+ * Will be removed once the conversion to VMA flags is complete.
+ */
+static __always_inline vm_flags_t vma_flags_to_legacy(vma_flags_t flags)
+{
+ return (vm_flags_t)flags.__vma_flags[0];
+}
+
+/*
+ * Helper function which converts a legacy vm_flags_t value to a vma_flags_t
+ * value.
+ *
+ * Will be removed once the conversion to VMA flags is complete.
+ */
+static __always_inline vma_flags_t legacy_to_vma_flags(vm_flags_t flags)
+{
+ vma_flags_t ret = EMPTY_VMA_FLAGS;
+
+ vma_flags_overwrite_word(&ret, flags);
+ return ret;
+}
+
static __always_inline void vma_flags_set_flag(vma_flags_t *flags,
vma_flag_t bit)
{
--
2.53.0