When we traverse anon_vma, we need to take a read-side anon_lock.
But there is subtle difference in the situation so that we can't use
same method to take a lock in each cases. Therefore, we need to make
rmap_walk_anon() taking difference lock function.
This patch is the first step, factoring lock function for anon_lock out
of rmap_walk_anon(). It will be used in case of removing migration entry
and in default of rmap_walk_anon().
Signed-off-by: Joonsoo Kim <iamjoonsoo....@lge.com>
diff --git a/mm/rmap.c b/mm/rmap.c
index e6d532c..916f2ed 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1683,6 +1683,24 @@ void __put_anon_vma(struct anon_vma *anon_vma)
}
#ifdef CONFIG_MIGRATION
+static struct anon_vma *rmap_walk_anon_lock(struct page *page)
+{
+ struct anon_vma *anon_vma;
+
+ /*
+ * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
+ * because that depends on page_mapped(); but not all its usages
+ * are holding mmap_sem. Users without mmap_sem are required to
+ * take a reference count to prevent the anon_vma disappearing
+ */
+ anon_vma = page_anon_vma(page);
+ if (!anon_vma)
+ return NULL;
+
+ anon_vma_lock_read(anon_vma);
+ return anon_vma;
+}
+
/*
* rmap_walk() and its helpers rmap_walk_anon() and rmap_walk_file():
* Called by migrate.c to remove migration ptes, but might be used more later.
@@ -1695,16 +1713,10 @@ static int rmap_walk_anon(struct page *page, int
(*rmap_one)(struct page *,
struct anon_vma_chain *avc;
int ret = SWAP_AGAIN;
- /*
- * Note: remove_migration_ptes() cannot use page_lock_anon_vma_read()
- * because that depends on page_mapped(); but not all its usages
- * are holding mmap_sem. Users without mmap_sem are required to
- * take a reference count to prevent the anon_vma disappearing
- */
- anon_vma = page_anon_vma(page);
+ anon_vma = rmap_walk_anon_lock(page);
if (!anon_vma)
return ret;
- anon_vma_lock_read(anon_vma);
+
anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
struct vm_area_struct *vma = avc->vma;
unsigned long address = vma_address(page, vma);
--
1.7.9.5
--
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