[PATCH] mm: fix panic caused by __page_handle_poison()

[王贇]

By commit 510d25c92ec4 ("mm/hwpoison: disable pcp for
page_handle_poison()"), __page_handle_poison() was
introduced, and if we mark:

RET_A = dissolve_free_huge_page();
RET_B = take_page_off_buddy();

then __page_handle_poison was supposed to return TRUE When
RET_A == 0 && RET_B == TRUE

But since it failed to take care the case when RET_A is
-EBUSY or -ENOMEM, and just return the ret as a bool which
actually become TRUE, it break the original logical.

The following result is a huge page in freelist but was
referenced as poisoned, and lead into the final panic:

  kernel BUG at mm/internal.h:95!
  invalid opcode: 0000 [#1] SMP PTI
  skip...
  RIP: 0010:set_page_refcounted mm/internal.h:95 [inline]
  RIP: 0010:remove_hugetlb_page+0x23c/0x240 mm/hugetlb.c:1371
  skip...
  Call Trace:
   remove_pool_huge_page+0xe4/0x110 mm/hugetlb.c:1892
   return_unused_surplus_pages+0x8d/0x150 mm/hugetlb.c:2272
   hugetlb_acct_memory.part.91+0x524/0x690 mm/hugetlb.c:4017

This patch replace 'bool' with 'int' to handle RET_A correctly.

Reported-by: Abaci <abaci@xxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Wang <yun.wang@xxxxxxxxxxxxxxxxx>
---
 mm/memory-failure.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 470400c..0fff717 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -68,7 +68,7 @@

 static bool __page_handle_poison(struct page *page)
 {
-	bool ret;
+	int ret;

 	zone_pcp_disable(page_zone(page));
 	ret = dissolve_free_huge_page(page);
@@ -76,7 +76,7 @@ static bool __page_handle_poison(struct page *page)
 		ret = take_page_off_buddy(page);
 	zone_pcp_enable(page_zone(page));

-	return ret;
+	return ret > 0;
 }

 static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
-- 
1.8.3.1