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 <surenb@xxxxxxxxxx>
Reviewed-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 40 ++++++++++++++++++++++++++++++++++++++++
include/linux/mm_types.h | 10 +++++++++-
2 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8d636e895ee9..abb31103d060 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -627,6 +627,46 @@ 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 vm_flags_init(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 vm_flags_reset(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ vm_flags_init(vma, flags);
+}
+
+static inline void vm_flags_set(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 vm_flags_clear(struct vm_area_struct *vma,
+ vm_flags_t flags)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ ACCESS_PRIVATE(vma, __vm_flags) &= ~flags;
+}
+
+/*
+ * Use only when the order of set/clear operations is unimportant, otherwise
+ * use vm_flags_{set|clear} explicitly.
+ */
+static inline void vm_flags_mod(struct vm_area_struct *vma,
+ vm_flags_t set, vm_flags_t clear)
+{
+ mmap_assert_write_locked(vma->vm_mm);
+ vm_flags_init(vma, (vma->vm_flags | set) & ~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..da983aedb741 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 vm_flags_{init|reset|set|clear|mod} 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
