linux-kernel - [PATCH] zsmalloc: fix linking bug in init

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Date:   Thu,  9 Aug 2018 20:28:17 -0400
From:   zhouxianrong <zhouxianrong@....com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, minchan@...nel.org,
        ngupta@...are.org, sergey.senozhatsky.work@...il.com,
        zhouxianrong@....com, zhouxianrong <zhouxianrong@...wei.com>
Subject: [PATCH] zsmalloc: fix linking bug in init_zspage

From: zhouxianrong <zhouxianrong@...wei.com>

The last partial object in last subpage of zspage should not be linked
in allocation list. Otherwise it could trigger BUG_ON explicitly at
function zs_map_object. But it happened rarely.

Signed-off-by: zhouxianrong <zhouxianrong@...wei.com>
---
 mm/zsmalloc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 8d87e973a4f5..24dd8da0aa59 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1040,6 +1040,8 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
 			 * Reset OBJ_TAG_BITS bit to last link to tell
 			 * whether it's allocated object or not.
 			 */
+			if (off > PAGE_SIZE)
+				link -= class->size / sizeof(*link);
 			link->next = -1UL << OBJ_TAG_BITS;
 		}
 		kunmap_atomic(vaddr);
-- 
2.13.6