The patch titled
Subject: zsmalloc: fix obj_to_head use page_private(page) as value but not pointer
has been added to the -mm tree. Its filename is
zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer.patch
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------------------------------------------------------
From: Hui Zhu <zhuhui@xxxxxxxxxx>
Subject: zsmalloc: fix obj_to_head use page_private(page) as value but not pointer
In obj_malloc():
if (!class->huge)
/* record handle in the header of allocated chunk */
link->handle = handle;
else
/* record handle in first_page->private */
set_page_private(first_page, handle);
In the hugepage we save handle to private directly.
But in obj_to_head():
if (class->huge) {
VM_BUG_ON(!is_first_page(page));
return *(unsigned long *)page_private(page);
} else
return *(unsigned long *)obj;
It is used as a pointer.
The reason why there is no problem until now is huge-class page is born
with ZS_FULL so it can't be migrated. However, we need this patch for
future work: "VM-aware zsmalloced page migration" to reduce external
fragmentation.
Signed-off-by: Hui Zhu <zhuhui@xxxxxxxxxx>
Acked-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/zsmalloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/zsmalloc.c~zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer mm/zsmalloc.c
--- a/mm/zsmalloc.c~zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer
+++ a/mm/zsmalloc.c
@@ -825,7 +825,7 @@ static unsigned long obj_to_head(struct
{
if (class->huge) {
VM_BUG_ON(!is_first_page(page));
- return *(unsigned long *)page_private(page);
+ return page_private(page);
} else
return *(unsigned long *)obj;
}
_
Patches currently in -mm which might be from zhuhui@xxxxxxxxxx are
zsmalloc-add-comments-for-inuse-to-zspage.patch
zsmalloc-fix-obj_to_head-use-page_privatepage-as-value-but-not-pointer.patch
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