On Mon, Jun 06, 2016 at 11:11:51PM +0300, Dan Carpenter wrote:
> Hello Minchan Kim,
>
> The patch 312fcae22703: "zsmalloc: support compaction" from Apr 15,
> 2015, leads to the following static checker warning:
>
> mm/zsmalloc.c:1521 obj_malloc()
> warn: 'OBJ_ALLOCATED_TAG' is a shifter (not for '|=').
>
> mm/zsmalloc.c
> 1510 static unsigned long obj_malloc(struct size_class *class,
> 1511 struct zspage *zspage, unsigned long handle)
> 1512 {
> 1513 int i, nr_page, offset;
> 1514 unsigned long obj;
> 1515 struct link_free *link;
> 1516
> 1517 struct page *m_page;
> 1518 unsigned long m_offset;
> 1519 void *vaddr;
> 1520
> 1521 handle |= OBJ_ALLOCATED_TAG;
> ^^^^^^^^^^^^^^^^^
> It's weird to use the same define for a bit number
>
> 1522 obj = get_freeobj(zspage);
> 1523
> 1524 offset = obj * class->size;
> 1525 nr_page = offset >> PAGE_SHIFT;
> 1526 m_offset = offset & ~PAGE_MASK;
> 1527 m_page = get_first_page(zspage);
> 1528
> 1529 for (i = 0; i < nr_page; i++)
> 1530 m_page = get_next_page(m_page);
> 1531
> 1532 vaddr = kmap_atomic(m_page);
> 1533 link = (struct link_free *)vaddr + m_offset / sizeof(*link);
> 1534 set_freeobj(zspage, link->next >> OBJ_ALLOCATED_TAG);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> And also a bit shifter. TAG normally implies it is a bit and not a
> shift?
Thanks for the report, Dan!
>From 42d08096ad7ea255fad36da215fea4c148b919f8 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@xxxxxxxxxx>
Date: Tue, 7 Jun 2016 13:46:09 +0900
Subject: [PATCH] zsmalloc: use OBJ_TAG_BIT for bit shifter
Static check warns using tag as bit shifter. It doesn't break
current working but not good for redability.
Let's use OBJ_TAG_BIT as bit shifter instead of OBJ_ALLOCATED_TAG.
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
---
mm/zsmalloc.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index a575b47e6c92..aec70d741503 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1065,7 +1065,7 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
link = (struct link_free *)vaddr + off / sizeof(*link);
while ((off += class->size) < PAGE_SIZE) {
- link->next = freeobj++ << OBJ_ALLOCATED_TAG;
+ link->next = freeobj++ << OBJ_TAG_BITS;
link += class->size / sizeof(*link);
}
@@ -1076,13 +1076,13 @@ static void init_zspage(struct size_class *class, struct zspage *zspage)
*/
next_page = get_next_page(page);
if (next_page) {
- link->next = freeobj++ << OBJ_ALLOCATED_TAG;
+ link->next = freeobj++ << OBJ_TAG_BITS;
} else {
/*
- * Reset OBJ_ALLOCATED_TAG bit to last link to tell
+ * Reset OBJ_TAG_BITS bit to last link to tell
* whether it's allocated object or not.
*/
- link->next = -1 << OBJ_ALLOCATED_TAG;
+ link->next = -1 << OBJ_TAG_BITS;
}
kunmap_atomic(vaddr);
page = next_page;
@@ -1531,7 +1531,7 @@ static unsigned long obj_malloc(struct size_class *class,
vaddr = kmap_atomic(m_page);
link = (struct link_free *)vaddr + m_offset / sizeof(*link);
- set_freeobj(zspage, link->next >> OBJ_ALLOCATED_TAG);
+ set_freeobj(zspage, link->next >> OBJ_TAG_BITS);
if (likely(!PageHugeObject(m_page)))
/* record handle in the header of allocated chunk */
link->handle = handle;
@@ -1633,7 +1633,7 @@ static void obj_free(struct size_class *class, unsigned long obj)
/* Insert this object in containing zspage's freelist */
link = (struct link_free *)(vaddr + f_offset);
- link->next = get_freeobj(zspage) << OBJ_ALLOCATED_TAG;
+ link->next = get_freeobj(zspage) << OBJ_TAG_BITS;
kunmap_atomic(vaddr);
set_freeobj(zspage, f_objidx);
mod_zspage_inuse(zspage, -1);
--
1.9.1
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