vm_flags are among VMA attributes which affect decisions like VMA merging
and splitting. Therefore all vm_flags modifications are performed after
taking exclusive mmap_lock to prevent vm_flags updates racing with such
operations. Introduce modifier functions for vm_flags to be used whenever
flags are updated. This way we can better check and control correct
locking behavior during these updates.
Signed-off-by: Suren Baghdasaryan <sur...@google.com>
---
include/linux/mm.h | 37 +++++++++++++++++++++++++++++++++++++
include/linux/mm_types.h | 10 +++++++++-
2 files changed, 46 insertions(+), 1 deletion(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c2f62bdce134..bf16ddd544a5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -627,6 +627,43 @@ static inline void vma_init(struct vm_area_struct *vma,
struct mm_struct *mm)
INIT_LIST_HEAD(&vma->anon_vma_chain);
}
+/* Use when VMA is not part of the VMA tree and needs no locking */
+static inline void init_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ ACCESS_PRIVATE(vma, __vm_flags) = flags;
+}
+
+/* Use when VMA is part of the VMA tree and modifications need coordination */
+static inline void reset_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ init_vm_flags(vma, flags);
+}
+
+static inline void set_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ ACCESS_PRIVATE(vma, __vm_flags) |= flags;
+}
+
+static inline void clear_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
+}
+
+static inline void mod_vm_flags(struct vm_area_struct *vma,
+ vm_flags_t set, vm_flags_t clear)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ ACCESS_PRIVATE(vma, __vm_flags) |= set;
+ ACCESS_PRIVATE(vma, __vm_flags) &= ~clear;
+}
+
static inline void vma_set_anonymous(struct vm_area_struct *vma)
{
vma->vm_ops = NULL;
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 2d6d790d9bed..bccbd5896850 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -491,7 +491,15 @@ struct vm_area_struct {
* See vmf_insert_mixed_prot() for discussion.
*/
pgprot_t vm_page_prot;
- unsigned long vm_flags; /* Flags, see mm.h. */
+
+ /*
+ * Flags, see mm.h.
+ * To modify use {init|reset|set|clear|mod}_vm_flags() functions.
+ */
+ union {
+ const vm_flags_t vm_flags;
+ vm_flags_t __private __vm_flags;
+ };
/*
* For areas with an address space and backing store,
--
2.39.1
