[PATCH 5/8] thp, mm: locking tail page is a bug

[Kirill A. Shutemov]

From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

Locking head page means locking entire compound page.
If we try to lock tail page, something went wrong.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
---
 mm/filemap.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/filemap.c b/mm/filemap.c
index f7c4ed5..e59049c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -639,6 +639,7 @@ void __lock_page(struct page *page)
 {
 	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 
+	VM_BUG_ON(PageTail(page));
 	__wait_on_bit_lock(page_waitqueue(page), &wait, sleep_on_page,
 							TASK_UNINTERRUPTIBLE);
 }
@@ -648,6 +649,7 @@ int __lock_page_killable(struct page *page)
 {
 	DEFINE_WAIT_BIT(wait, &page->flags, PG_locked);
 
+	VM_BUG_ON(PageTail(page));
 	return __wait_on_bit_lock(page_waitqueue(page), &wait,
 					sleep_on_page_killable, TASK_KILLABLE);
 }
-- 
1.8.3.2

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