On 13.09.21 13:50, Miaohe Lin wrote:
If __isolate_free_page() failed, due to zone watermark check, the page is
still on the free list. But this page will be put back to free list again
via __putback_isolated_page() now. This may trigger page->flags checks in
__free_one_page() if PageReported is set. Or we will corrupt the free list
because list_add() will be called for pages already on another list.
Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
v1->v2:
Add VM_WARN_ON to catch unexpected isolating failure.
---
mm/page_isolation.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index f93cc63d8fa1..f67c4c70f17f 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
buddy = page + (buddy_pfn - pfn);
if (!is_migrate_isolate_page(buddy)) {
- __isolate_free_page(page, order);
- isolated_page = true;
+ isolated_page = !!__isolate_free_page(page, order);
+ /*
+ * Isolating a free page in an isolated pageblock
+ * is expected to always work as watermarks don't
+ * apply here.
+ */
+ VM_WARN_ON(!isolated_page);
Didn't we discuss that this can never happen?
In that case, the patch description+subject needs updating and the
"Fixes" line would be wrong.
}
}
}
--
Thanks,
David / dhildenb
