This prepares for speculative page faults looking up and copying vmas
under protection of an rcu read lock, instead of the usual mmap read lock.
Signed-off-by: Michel Lespinasse <michel@xxxxxxxxxxxxxx>
---
include/linux/mm_types.h | 16 +++++++++++-----
kernel/fork.c | 11 ++++++++++-
2 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 70882e628908..024970635921 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -304,12 +304,18 @@ struct vm_userfaultfd_ctx {};
struct vm_area_struct {
/* The first cache line has the info for VMA tree walking. */
- unsigned long vm_start; /* Our start address within vm_mm. */
- unsigned long vm_end; /* The first byte after our end address
- within vm_mm. */
+ union {
+ struct {
+ /* VMA covers [vm_start; vm_end) addresses within mm */
+ unsigned long vm_start, vm_end;
- /* linked list of VM areas per task, sorted by address */
- struct vm_area_struct *vm_next, *vm_prev;
+ /* linked list of VMAs per task, sorted by address */
+ struct vm_area_struct *vm_next, *vm_prev;
+ };
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+ struct rcu_head vm_rcu; /* Used for deferred freeing. */
+#endif
+ };
struct rb_node vm_rb;
diff --git a/kernel/fork.c b/kernel/fork.c
index 426cd0c51f9e..b6078e546114 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -369,11 +369,20 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
return new;
}
-void vm_area_free(struct vm_area_struct *vma)
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+static void __vm_area_free(struct rcu_head *head)
{
+ struct vm_area_struct *vma = container_of(head, struct vm_area_struct,
+ vm_rcu);
kmem_cache_free(vm_area_cachep, vma);
}
+void vm_area_free(struct vm_area_struct *vma)
+{
+ call_rcu(&vma->vm_rcu, __vm_area_free);
+}
+#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */
+
static void account_kernel_stack(struct task_struct *tsk, int account)
{
void *stack = task_stack_page(tsk);
--
2.20.1
