[ 31/82] mm: setup pageblock_order before its used by sparsemem

From: Greg Kroah-Hartman
Date: Mon Aug 13 2012 - 16:39:02 EST


From: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>

3.5-stable review patch. If anyone has any objections, please let me know.

------------------

From: Xishi Qiu <qiuxishi@xxxxxxxxxx>

commit ca57df79d4f64e1a4886606af4289d40636189c5 upstream.

On architectures with CONFIG_HUGETLB_PAGE_SIZE_VARIABLE set, such as
Itanium, pageblock_order is a variable with default value of 0. It's set
to the right value by set_pageblock_order() in function
free_area_init_core().

But pageblock_order may be used by sparse_init() before free_area_init_core()
is called along path:
sparse_init()
->sparse_early_usemaps_alloc_node()
->usemap_size()
->SECTION_BLOCKFLAGS_BITS
->((1UL << (PFN_SECTION_SHIFT - pageblock_order)) *
NR_PAGEBLOCK_BITS)

The uninitialized pageblock_size will cause memory wasting because
usemap_size() returns a much bigger value then it's really needed.

For example, on an Itanium platform,
sparse_init() pageblock_order=0 usemap_size=24576
free_area_init_core() before pageblock_order=0, usemap_size=24576
free_area_init_core() after pageblock_order=12, usemap_size=8

That means 24K memory has been wasted for each section, so fix it by calling
set_pageblock_order() from sparse_init().

Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Signed-off-by: Jiang Liu <liuj97@xxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Keping Chen <chenkeping@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
mm/internal.h | 2 ++
mm/page_alloc.c | 4 ++--
mm/sparse.c | 3 +++
3 files changed, 7 insertions(+), 2 deletions(-)

--- a/mm/internal.h
+++ b/mm/internal.h
@@ -347,3 +347,5 @@ extern u32 hwpoison_filter_enable;
extern unsigned long vm_mmap_pgoff(struct file *, unsigned long,
unsigned long, unsigned long,
unsigned long, unsigned long);
+
+extern void set_pageblock_order(void);
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4301,7 +4301,7 @@ static inline void setup_usemap(struct p
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE

/* Initialise the number of pages represented by NR_PAGEBLOCK_BITS */
-static inline void __init set_pageblock_order(void)
+void __init set_pageblock_order(void)
{
unsigned int order;

@@ -4329,7 +4329,7 @@ static inline void __init set_pageblock_
* include/linux/pageblock-flags.h for the values of pageblock_order based on
* the kernel config
*/
-static inline void set_pageblock_order(void)
+void __init set_pageblock_order(void)
{
}

--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -493,6 +493,9 @@ void __init sparse_init(void)
struct page **map_map;
#endif

+ /* Setup pageblock_order for HUGETLB_PAGE_SIZE_VARIABLE */
+ set_pageblock_order();
+
/*
* map is using big page (aka 2M in x86 64 bit)
* usemap is less one page (aka 24 bytes)


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