[PATCH] remove_from_swap: fix locking
remove_from_swap() currently attempts to use page_lock_anon_vma to obtain
an anon_vma lock. That is not working since the page may have been
remapped via swap ptes in order to move the page.
However, do_migrate_pages() obtain the mmap_sem lock and therefore there is
a guarantee that the anonymous vma will not vanish from under us. There is
therefore no need to use page_lock_anon_vma.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/rmap.c b/mm/rmap.c
index df2c41c..d8ce5ff 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -212,25 +212,33 @@
* through real pte's pointing to valid pages and then releasing
* the page from the swap cache.
*
- * Must hold page lock on page.
+ * Must hold page lock on page and mmap_sem of one vma that contains
+ * the page.
*/
void remove_from_swap(struct page *page)
{
struct anon_vma *anon_vma;
struct vm_area_struct *vma;
+ unsigned long mapping;
- if (!PageAnon(page) || !PageSwapCache(page))
+ if (!PageSwapCache(page))
return;
- anon_vma = page_lock_anon_vma(page);
- if (!anon_vma)
+ mapping = (unsigned long)page->mapping;
+
+ if (!mapping || (mapping & PAGE_MAPPING_ANON) == 0)
return;
+ /*
+ * We hold the mmap_sem lock. So no need to call page_lock_anon_vma.
+ */
+ anon_vma = (struct anon_vma *) (mapping - PAGE_MAPPING_ANON);
+ spin_lock(&anon_vma->lock);
+
list_for_each_entry(vma, &anon_vma->head, anon_vma_node)
remove_vma_swap(vma, page);
spin_unlock(&anon_vma->lock);
-
delete_from_swap_cache(page);
}
EXPORT_SYMBOL(remove_from_swap);