mm: more checks on free_pages_prepare() for tail pages
Although it was not called, destroy_compound_page() did some potentially
useful checks. Let's re-introduce them in free_pages_prepare(), where
they can be actually triggered when CONFIG_DEBUG_VM=y.
compound_order() assert is already in free_pages_prepare(). We have few
checks for tail pages left.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 12d55b8..0081228 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -764,21 +764,40 @@
spin_unlock(&zone->lock);
}
+static int free_tail_pages_check(struct page *head_page, struct page *page)
+{
+ if (!IS_ENABLED(CONFIG_DEBUG_VM))
+ return 0;
+ if (unlikely(!PageTail(page))) {
+ bad_page(page, "PageTail not set", 0);
+ return 1;
+ }
+ if (unlikely(page->first_page != head_page)) {
+ bad_page(page, "first_page not consistent", 0);
+ return 1;
+ }
+ return 0;
+}
+
static bool free_pages_prepare(struct page *page, unsigned int order)
{
- int i;
- int bad = 0;
+ bool compound = PageCompound(page);
+ int i, bad = 0;
VM_BUG_ON_PAGE(PageTail(page), page);
- VM_BUG_ON_PAGE(PageHead(page) && compound_order(page) != order, page);
+ VM_BUG_ON_PAGE(compound && compound_order(page) != order, page);
trace_mm_page_free(page, order);
kmemcheck_free_shadow(page, order);
if (PageAnon(page))
page->mapping = NULL;
- for (i = 0; i < (1 << order); i++)
+ bad += free_pages_check(page);
+ for (i = 1; i < (1 << order); i++) {
+ if (compound)
+ bad += free_tail_pages_check(page, page + i);
bad += free_pages_check(page + i);
+ }
if (bad)
return false;