From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Wed, 20 Oct 2021 18:54:18 +0000 (-0400)
Subject: fixy-fixy
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=47b21587dc902192d13b3a0ae58e2c9b836618fe;p=users%2Fwilly%2Flinux.git

fixy-fixy
---

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 87f4f53a3d7d..2ca7cc6c903b 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -50,6 +50,8 @@ static inline void mmdrop(struct mm_struct *mm)
 		__mmdrop(mm);
 }
 
+void mm_set_in_rcu(struct mm_struct *mm);
+
 /**
  * mmget() - Pin the address space associated with a &struct mm_struct.
  * @mm: The address space to pin.
@@ -68,7 +70,8 @@ static inline void mmdrop(struct mm_struct *mm)
  */
 static inline void mmget(struct mm_struct *mm)
 {
-	mt_set_in_rcu(&mm->mm_mt);
+	if (!mt_in_rcu(&mm->mm_mt))
+		mm_set_in_rcu(mm);
 	atomic_inc(&mm->mm_users);
 }
 
@@ -80,7 +83,8 @@ static inline bool mmget_not_zero(struct mm_struct *mm)
 	 * happens, the result would be that the maple tree nodes would remain
 	 * active for an extra RCU read cycle.
 	 */
-	mt_set_in_rcu(&mm->mm_mt);
+	if (!mt_in_rcu(&mm->mm_mt))
+		mm_set_in_rcu(mm);
 	return atomic_inc_not_zero(&mm->mm_users);
 }
 
diff --git a/kernel/fork.c b/kernel/fork.c
index 3b0b0e1fe164..08a3c9f3861c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -617,11 +617,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 		rb_parent = &tmp->vm_rb;
 
 		/* Link the vma into the MT */
-		mas_lock(&mas);
 		mas.index = tmp->vm_start;
 		mas.last = tmp->vm_end - 1;
 		mas_store(&mas, tmp);
-		mas_unlock(&mas);
 
 		mm->map_count++;
 		if (!(tmp->vm_flags & VM_WIPEONFORK))
diff --git a/mm/mmap.c b/mm/mmap.c
index 7c011dd96e5a..83cb19763d90 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -309,6 +309,15 @@ static inline unsigned long vma_compute_gap(struct vm_area_struct *vma)
 	return gap;
 }
 
+void mm_set_in_rcu(struct mm_struct *mm)
+{
+	if (!mt_in_rcu(&mm->mm_mt))
+		return;
+	mmap_write_lock(mm);
+	mm->mm_mt.ma_flags |= MT_FLAGS_USE_RCU;
+	mmap_write_unlock(mm);
+}
+
 #ifdef CONFIG_DEBUG_VM_RB
 static unsigned long vma_compute_subtree_gap(struct vm_area_struct *vma)
 {
@@ -3192,7 +3201,6 @@ void exit_mmap(struct mm_struct *mm)
 	mmap_write_lock(mm);
 	__mt_destroy(&mm->mm_mt);
 	mmap_write_unlock(mm);
-
 	vm_unacct_memory(nr_accounted);
 }