* re: zsmalloc: zs_compact refactoring
@ 2016-04-04 20:39 Dan Carpenter
2016-04-07 2:39 ` Minchan Kim
0 siblings, 1 reply; 2+ messages in thread
From: Dan Carpenter @ 2016-04-04 20:39 UTC (permalink / raw)
To: minchan; +Cc: Sergey Senozhatsky, linux-mm
Hello Minchan Kim,
The patch 9a0346061ab8: "zsmalloc: zs_compact refactoring" from Apr
2, 2016, leads to the following static checker warning:
mm/zsmalloc.c:1851 handle_from_obj()
warn: bit shifter 'OBJ_ALLOCATED_TAG' used for logical '&'
mm/zsmalloc.c
1622 static unsigned long obj_malloc(struct size_class *class,
1623 struct page *first_page, unsigned long handle)
1624 {
1625 unsigned long obj;
1626 struct link_free *link;
1627
1628 struct page *m_page;
1629 unsigned long m_offset;
1630 void *vaddr;
1631
1632 obj = get_freeobj(first_page);
1633 objidx_to_page_and_offset(class, first_page, obj,
1634 &m_page, &m_offset);
1635
1636 vaddr = kmap_atomic(m_page);
1637 link = (struct link_free *)vaddr + m_offset / sizeof(*link);
1638 set_freeobj(first_page, link->next >> OBJ_ALLOCATED_TAG);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
OBJ_ALLOCATED_TAG is 1. Here it's used as a shifter.
1639 if (!class->huge)
1640 /* record handle in the header of allocated chunk */
1641 link->handle = handle | OBJ_ALLOCATED_TAG;
Here it's a bit mask. It's sort of confusing to re-use it like this.
It's done through out the file.
1642 else
1643 /* record handle in first_page->private */
1644 set_page_private(first_page, handle | OBJ_ALLOCATED_TAG);
1645 kunmap_atomic(vaddr);
1646 mod_zspage_inuse(first_page, 1);
1647
1648 obj = location_to_obj(m_page, obj);
1649
1650 return obj;
1651 }
regards,
dan carpenter
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^ permalink raw reply [flat|nested] 2+ messages in thread* Re: zsmalloc: zs_compact refactoring
2016-04-04 20:39 zsmalloc: zs_compact refactoring Dan Carpenter
@ 2016-04-07 2:39 ` Minchan Kim
0 siblings, 0 replies; 2+ messages in thread
From: Minchan Kim @ 2016-04-07 2:39 UTC (permalink / raw)
To: Dan Carpenter; +Cc: Sergey Senozhatsky, linux-mm
Hello Dan,
On Mon, Apr 04, 2016 at 11:39:52PM +0300, Dan Carpenter wrote:
> Hello Minchan Kim,
>
> The patch 9a0346061ab8: "zsmalloc: zs_compact refactoring" from Apr
> 2, 2016, leads to the following static checker warning:
>
> mm/zsmalloc.c:1851 handle_from_obj()
> warn: bit shifter 'OBJ_ALLOCATED_TAG' used for logical '&'
>
> mm/zsmalloc.c
> 1622 static unsigned long obj_malloc(struct size_class *class,
> 1623 struct page *first_page, unsigned long handle)
> 1624 {
> 1625 unsigned long obj;
> 1626 struct link_free *link;
> 1627
> 1628 struct page *m_page;
> 1629 unsigned long m_offset;
> 1630 void *vaddr;
> 1631
> 1632 obj = get_freeobj(first_page);
> 1633 objidx_to_page_and_offset(class, first_page, obj,
> 1634 &m_page, &m_offset);
> 1635
> 1636 vaddr = kmap_atomic(m_page);
> 1637 link = (struct link_free *)vaddr + m_offset / sizeof(*link);
> 1638 set_freeobj(first_page, link->next >> OBJ_ALLOCATED_TAG);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> OBJ_ALLOCATED_TAG is 1. Here it's used as a shifter.
>
> 1639 if (!class->huge)
> 1640 /* record handle in the header of allocated chunk */
> 1641 link->handle = handle | OBJ_ALLOCATED_TAG;
>
> Here it's a bit mask. It's sort of confusing to re-use it like this.
> It's done through out the file.
I will send clean up patch.
Thanks.
>
> 1642 else
> 1643 /* record handle in first_page->private */
> 1644 set_page_private(first_page, handle | OBJ_ALLOCATED_TAG);
> 1645 kunmap_atomic(vaddr);
> 1646 mod_zspage_inuse(first_page, 1);
> 1647
> 1648 obj = location_to_obj(m_page, obj);
> 1649
> 1650 return obj;
> 1651 }
>
> regards,
> dan carpenter
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