[PATCH] mm/rmap: remove unnecessary page_table_lock

[Yajun Deng]

page_table_lock is a lock that for page table, we won't change page
table in __anon_vma_prepare(). As we can see, it works well in
anon_vma_clone(). They do the same operation.

Remove unnecessary page_table_lock in __anon_vma_prepare().

Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
---
 mm/rmap.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 2608c40dffad..e894640a9327 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -187,7 +187,6 @@ static void anon_vma_chain_link(struct vm_area_struct *vma,
  */
 int __anon_vma_prepare(struct vm_area_struct *vma)
 {
-	struct mm_struct *mm = vma->vm_mm;
 	struct anon_vma *anon_vma, *allocated;
 	struct anon_vma_chain *avc;
 
@@ -208,8 +207,6 @@ int __anon_vma_prepare(struct vm_area_struct *vma)
 	}
 
 	anon_vma_lock_write(anon_vma);
-	/* page_table_lock to protect against threads */
-	spin_lock(&mm->page_table_lock);
 	if (likely(!vma->anon_vma)) {
 		vma->anon_vma = anon_vma;
 		anon_vma_chain_link(vma, avc, anon_vma);
@@ -217,7 +214,6 @@ int __anon_vma_prepare(struct vm_area_struct *vma)
 		allocated = NULL;
 		avc = NULL;
 	}
-	spin_unlock(&mm->page_table_lock);
 	anon_vma_unlock_write(anon_vma);
 
 	if (unlikely(allocated))
-- 
2.25.1