File _service:download_files:vma-detached.diff of Package linux-px

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File _service:download_files:vma-detached.diff of Package linux-px (Revision accc70307e72cfe71a163f911055545d)

Currently displaying revision accc70307e72cfe71a163f911055545d , Show latest

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3494d49b0dd7aa..ef9a94d076fa4e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -247,7 +247,7 @@ void setup_initial_init_mm(void *start_code, void *end_code,
 struct vm_area_struct *vm_area_alloc(struct mm_struct *);
 struct vm_area_struct *vm_area_dup(struct vm_area_struct *);
 void vm_area_free(struct vm_area_struct *);
-/* Use only if VMA has no other users */
+/* Use only if VMA has no other users and might still be attached to a tree */
 void __vm_area_free(struct vm_area_struct *vma);
 
 #ifndef CONFIG_MMU
@@ -639,23 +639,24 @@ static inline void vma_numab_state_free(struct vm_area_struct *vma) {}
  */
 static inline bool vma_start_read(struct vm_area_struct *vma)
 {
-	/* Check before locking. A race might cause false locked result. */
-	if (vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq))
+	int vm_lock_seq = READ_ONCE(vma->vm_lock_seq);
+
+	/*
+	 * Check if VMA is locked before taking vma->vm_lock. A race or
+	 * mm_lock_seq overflow might cause false locked result.
+	 */
+	if (vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq))
 		return false;
 
 	if (unlikely(down_read_trylock(&vma->vm_lock->lock) == 0))
 		return false;
 
-	/*
-	 * Overflow might produce false locked result.
-	 * False unlocked result is impossible because we modify and check
-	 * vma->vm_lock_seq under vma->vm_lock protection and mm->mm_lock_seq
-	 * modification invalidates all existing locks.
-	 */
-	if (unlikely(vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq))) {
+	/* Fail if VMA is detached or was write-locked after we checked it earlier */
+	if (unlikely(vma->detached || vm_lock_seq != READ_ONCE(vma->vm_lock_seq))) {
 		up_read(&vma->vm_lock->lock);
 		return false;
 	}
+
 	return true;
 }
 
@@ -749,7 +750,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 	vma->vm_mm = mm;
 	vma->vm_ops = &dummy_vm_ops;
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
-	vma_mark_detached(vma, false);
+	vma->detached = true;
 	vma_numab_state_init(vma);
 }
 
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 8abfa124004003..e741098954ff8c 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -154,7 +154,6 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
 		VMA_LOCK_SUCCESS,
 		VMA_LOCK_ABORT,
 		VMA_LOCK_RETRY,
-		VMA_LOCK_MISS,
 #endif
 		NR_VM_EVENT_ITEMS
 };
diff --git a/kernel/fork.c b/kernel/fork.c
index d17995934eb483..630410fc0d6bd7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -536,6 +536,7 @@ static void vm_area_free_rcu_cb(struct rcu_head *head)
 
 	/* The vma should not be locked while being destroyed. */
 	VM_BUG_ON_VMA(rwsem_is_locked(&vma->vm_lock->lock), vma);
+	WARN_ON_ONCE(!vma->detached);
 	__vm_area_free(vma);
 }
 #endif
@@ -545,6 +546,7 @@ void vm_area_free(struct vm_area_struct *vma)
 #ifdef CONFIG_PER_VMA_LOCK
 	call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb);
 #else
+	WARN_ON_ONCE(!vma->detached);
 	__vm_area_free(vma);
 #endif
 }
diff --git a/mm/internal.h b/mm/internal.h
index b0d8778dd91023..7e9c69a792a0f7 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1077,6 +1077,7 @@ static inline void vma_iter_store(struct vma_iterator *vmi,
 	vmi->mas.index = vma->vm_start;
 	vmi->mas.last = vma->vm_end - 1;
 	mas_store_prealloc(&vmi->mas, vma);
+	vma_mark_detached(vma, false);
 }
 
 static inline int vma_iter_store_gfp(struct vma_iterator *vmi,
diff --git a/mm/memory.c b/mm/memory.c
index 0a6ec8da275308..6ccf0199e6e7d7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5260,7 +5260,7 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
 	struct vm_area_struct *vma;
 
 	rcu_read_lock();
-retry:
+
 	vma = mas_walk(&mas);
 	if (!vma)
 		goto inval;
@@ -5291,14 +5291,6 @@ struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
 		goto inval;
 	}
 
-	/* Check if the VMA got isolated after we found it */
-	if (vma->detached) {
-		vma_end_read(vma);
-		count_vm_vma_lock_event(VMA_LOCK_MISS);
-		/* The area was replaced with another one */
-		goto retry;
-	}
-
 	rcu_read_unlock();
 	return vma;
 inval:
diff --git a/mm/vmstat.c b/mm/vmstat.c
index c7499e3ee9d551..d7287cb75aa60e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1404,7 +1404,6 @@ const char * const vmstat_text[] = {
 	"vma_lock_success",
 	"vma_lock_abort",
 	"vma_lock_retry",
-	"vma_lock_miss",
 #endif
 #endif /* CONFIG_VM_EVENT_COUNTERS || CONFIG_MEMCG */
 };

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File _service:download_files:vma-detached.diff of Package linux-px (Revision accc70307e72cfe71a163f911055545d)

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