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From:   Wei Yang <richard.weiyang@linux.alibaba.com>
To:     mike.kravetz@oracle.com, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Wei Yang <richard.weiyang@linux.alibaba.com>
Subject: [PATCH 02/10] mm/hugetlb: make sure to get NULL when list is empty
Date:   Fri,  7 Aug 2020 17:12:43 +0800
Message-Id: <20200807091251.12129-3-richard.weiyang@linux.alibaba.com>
In-Reply-To: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com>
References: <20200807091251.12129-1-richard.weiyang@linux.alibaba.com>
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list_first_entry() may not return NULL even when the list is empty.

Let's make sure the behavior by using list_first_entry_or_null(),
otherwise it would corrupt the list.

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
---
 mm/hugetlb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 62ec74f6d03f..0a2f3851b828 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -237,7 +237,8 @@ get_file_region_entry_from_cache(struct resv_map *resv, long from, long to)
 	VM_BUG_ON(resv->region_cache_count <= 0);
 
 	resv->region_cache_count--;
-	nrg = list_first_entry(&resv->region_cache, struct file_region, link);
+	nrg = list_first_entry_or_null(&resv->region_cache,
+			struct file_region, link);
 	VM_BUG_ON(!nrg);
 	list_del(&nrg->link);
 
-- 
2.20.1 (Apple Git-117)