[PATCH 1/2] mm/sparsemem: Use PAGES_PER_SECTION to remove redundant nr_pages parameter

[PATCH 1/2] mm/sparsemem: Use PAGES_PER_SECTION to remove redundant nr_pages parameter

[Zhang Yanfei]

From: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>

For below functions,
- sparse_add_one_section()
- kmalloc_section_memmap()
- __kmalloc_section_memmap()
- __kfree_section_memmap()
they are always invoked to operate on one memory section, so it is
redundant to always pass a nr_pages parameter, which is the page
numbers in one section. So we can directly use predefined marco
PAGES_PER_SECTION instead of passing the parameter.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
---
 include/linux/memory_hotplug.h |    3 +--
 mm/memory_hotplug.c            |    3 +--
 mm/sparse.c                    |   33 +++++++++++++++------------------
 3 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index dd38e62..57ac2a9 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -262,8 +262,7 @@ extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern bool is_memblock_offlined(struct memory_block *mem);
 extern void remove_memory(int nid, u64 start, u64 size);
-extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
-								int nr_pages);
+extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn);
 extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);
 extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map,
 					  unsigned long pnum);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index ed85fe3..d457bf8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -402,13 +402,12 @@ static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
 static int __meminit __add_section(int nid, struct zone *zone,
 					unsigned long phys_start_pfn)
 {
-	int nr_pages = PAGES_PER_SECTION;
 	int ret;
 
 	if (pfn_valid(phys_start_pfn))
 		return -EEXIST;
 
-	ret = sparse_add_one_section(zone, phys_start_pfn, nr_pages);
+	ret = sparse_add_one_section(zone, phys_start_pfn);
 
 	if (ret < 0)
 		return ret;
diff --git a/mm/sparse.c b/mm/sparse.c
index 4ac1d7e..fbb9dbc 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -590,16 +590,15 @@ void __init sparse_init(void)
 
 #ifdef CONFIG_MEMORY_HOTPLUG
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
-						 unsigned long nr_pages)
+static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid)
 {
 	/* This will make the necessary allocations eventually. */
 	return sparse_mem_map_populate(pnum, nid);
 }
-static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
+static void __kfree_section_memmap(struct page *memmap)
 {
 	unsigned long start = (unsigned long)memmap;
-	unsigned long end = (unsigned long)(memmap + nr_pages);
+	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
 
 	vmemmap_free(start, end);
 }
@@ -613,10 +612,10 @@ static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 #else
-static struct page *__kmalloc_section_memmap(unsigned long nr_pages)
+static struct page *__kmalloc_section_memmap(void)
 {
 	struct page *page, *ret;
-	unsigned long memmap_size = sizeof(struct page) * nr_pages;
+	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
 
 	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
 	if (page)
@@ -634,19 +633,18 @@ got_map_ptr:
 	return ret;
 }
 
-static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid,
-						  unsigned long nr_pages)
+static inline struct page *kmalloc_section_memmap(unsigned long pnum, int nid)
 {
-	return __kmalloc_section_memmap(nr_pages);
+	return __kmalloc_section_memmap();
 }
 
-static void __kfree_section_memmap(struct page *memmap, unsigned long nr_pages)
+static void __kfree_section_memmap(struct page *memmap)
 {
 	if (is_vmalloc_addr(memmap))
 		vfree(memmap);
 	else
 		free_pages((unsigned long)memmap,
-			   get_order(sizeof(struct page) * nr_pages));
+			   get_order(sizeof(struct page) * PAGES_PER_SECTION));
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
@@ -684,8 +682,7 @@ static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
  * set.  If this is <=0, then that means that the passed-in
  * map was not consumed and must be freed.
  */
-int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
-			   int nr_pages)
+int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn)
 {
 	unsigned long section_nr = pfn_to_section_nr(start_pfn);
 	struct pglist_data *pgdat = zone->zone_pgdat;
@@ -702,12 +699,12 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
 	ret = sparse_index_init(section_nr, pgdat->node_id);
 	if (ret < 0 && ret != -EEXIST)
 		return ret;
-	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, nr_pages);
+	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id);
 	if (!memmap)
 		return -ENOMEM;
 	usemap = __kmalloc_section_usemap();
 	if (!usemap) {
-		__kfree_section_memmap(memmap, nr_pages);
+		__kfree_section_memmap(memmap);
 		return -ENOMEM;
 	}
 
@@ -719,7 +716,7 @@ int __meminit sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
 		goto out;
 	}
 
-	memset(memmap, 0, sizeof(struct page) * nr_pages);
+	memset(memmap, 0, sizeof(struct page) * PAGES_PER_SECTION);
 
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 
@@ -729,7 +726,7 @@ out:
 	pgdat_resize_unlock(pgdat, &flags);
 	if (ret <= 0) {
 		kfree(usemap);
-		__kfree_section_memmap(memmap, nr_pages);
+		__kfree_section_memmap(memmap);
 	}
 	return ret;
 }
@@ -771,7 +768,7 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 	if (PageSlab(usemap_page) || PageCompound(usemap_page)) {
 		kfree(usemap);
 		if (memmap)
-			__kfree_section_memmap(memmap, PAGES_PER_SECTION);
+			__kfree_section_memmap(memmap);
 		return;
 	}
 
-- 
1.7.1

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[PATCH 2/2] mm/sparsemem: Fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

[Zhang Yanfei]

From: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>

We pass the number of pages which hold page structs of a memory
section to function free_map_bootmem. This is right when
!CONFIG_SPARSEMEM_VMEMMAP but wrong when CONFIG_SPARSEMEM_VMEMMAP.
When CONFIG_SPARSEMEM_VMEMMAP, we should pass the number of pages
of a memory section to free_map_bootmem.

So the fix is removing the nr_pages parameter. When
CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
PAGES_PER_SECTION in free_map_bootmem. When !CONFIG_SPARSEMEM_VMEMMAP,
we calculate page numbers needed to hold the page structs for a
memory section and use the value in free_map_bootmem.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
---
 mm/sparse.c |   17 +++++++----------
 1 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index fbb9dbc..908c134 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -603,10 +603,10 @@ static void __kfree_section_memmap(struct page *memmap)
 	vmemmap_free(start, end);
 }
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
+static void free_map_bootmem(struct page *memmap)
 {
 	unsigned long start = (unsigned long)memmap;
-	unsigned long end = (unsigned long)(memmap + nr_pages);
+	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
 
 	vmemmap_free(start, end);
 }
@@ -648,11 +648,13 @@ static void __kfree_section_memmap(struct page *memmap)
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
+static void free_map_bootmem(struct page *memmap)
 {
 	unsigned long maps_section_nr, removing_section_nr, i;
 	unsigned long magic;
 	struct page *page = virt_to_page(memmap);
+	unsigned long nr_pages = get_order(sizeof(struct page) *
+					   PAGES_PER_SECTION);
 
 	for (i = 0; i < nr_pages; i++, page++) {
 		magic = (unsigned long) page->lru.next;
@@ -756,7 +758,6 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
 static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 {
 	struct page *usemap_page;
-	unsigned long nr_pages;
 
 	if (!usemap)
 		return;
@@ -777,12 +778,8 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
 	 * on the section which has pgdat at boot time. Just keep it as is now.
 	 */
 
-	if (memmap) {
-		nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
-			>> PAGE_SHIFT;
-
-		free_map_bootmem(memmap, nr_pages);
-	}
+	if (memmap)
+		free_map_bootmem(memmap);
 }
 
 void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)
-- 
1.7.1

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Re: [PATCH 2/2] mm/sparsemem: Fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

[Andrew Morton]

On Thu, 03 Oct 2013 11:32:02 +0800 Zhang Yanfei <zhangyanfei.yes@gmail.com> wrote:

> We pass the number of pages which hold page structs of a memory
> section to function free_map_bootmem. This is right when
> !CONFIG_SPARSEMEM_VMEMMAP but wrong when CONFIG_SPARSEMEM_VMEMMAP.
> When CONFIG_SPARSEMEM_VMEMMAP, we should pass the number of pages
> of a memory section to free_map_bootmem.
> 
> So the fix is removing the nr_pages parameter. When
> CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
> PAGES_PER_SECTION in free_map_bootmem. When !CONFIG_SPARSEMEM_VMEMMAP,
> we calculate page numbers needed to hold the page structs for a
> memory section and use the value in free_map_bootmem.

What were the runtime user-visible effects of that bug?

Please always include this information when fixing a bug.

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Re: [PATCH 2/2] mm/sparsemem: Fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

[Wanpeng Li]

Hi Yanfei,
On Thu, Oct 03, 2013 at 11:32:02AM +0800, Zhang Yanfei wrote:
>From: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>
>We pass the number of pages which hold page structs of a memory
>section to function free_map_bootmem. This is right when
>!CONFIG_SPARSEMEM_VMEMMAP but wrong when CONFIG_SPARSEMEM_VMEMMAP.
>When CONFIG_SPARSEMEM_VMEMMAP, we should pass the number of pages
>of a memory section to free_map_bootmem.
>
>So the fix is removing the nr_pages parameter. When
>CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
>PAGES_PER_SECTION in free_map_bootmem. When !CONFIG_SPARSEMEM_VMEMMAP,
>we calculate page numbers needed to hold the page structs for a
>memory section and use the value in free_map_bootmem.
>
>Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>---
> mm/sparse.c |   17 +++++++----------
> 1 files changed, 7 insertions(+), 10 deletions(-)
>
>diff --git a/mm/sparse.c b/mm/sparse.c
>index fbb9dbc..908c134 100644
>--- a/mm/sparse.c
>+++ b/mm/sparse.c
>@@ -603,10 +603,10 @@ static void __kfree_section_memmap(struct page *memmap)
> 	vmemmap_free(start, end);
> }
> #ifdef CONFIG_MEMORY_HOTREMOVE
>-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
>+static void free_map_bootmem(struct page *memmap)
> {
> 	unsigned long start = (unsigned long)memmap;
>-	unsigned long end = (unsigned long)(memmap + nr_pages);
>+	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
>
> 	vmemmap_free(start, end);
> }
>@@ -648,11 +648,13 @@ static void __kfree_section_memmap(struct page *memmap)
> }
>
> #ifdef CONFIG_MEMORY_HOTREMOVE
>-static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
>+static void free_map_bootmem(struct page *memmap)
> {
> 	unsigned long maps_section_nr, removing_section_nr, i;
> 	unsigned long magic;
> 	struct page *page = virt_to_page(memmap);
>+	unsigned long nr_pages = get_order(sizeof(struct page) *
>+					   PAGES_PER_SECTION);

Why replace PAGE_ALIGN(XXX) >> PAGE_SHIFT by get_order(XXX)? This will result 
in memory leak.

Regards,
Wanpeng Li 

>
> 	for (i = 0; i < nr_pages; i++, page++) {
> 		magic = (unsigned long) page->lru.next;
>@@ -756,7 +758,6 @@ static inline void clear_hwpoisoned_pages(struct page *memmap, int nr_pages)
> static void free_section_usemap(struct page *memmap, unsigned long *usemap)
> {
> 	struct page *usemap_page;
>-	unsigned long nr_pages;
>
> 	if (!usemap)
> 		return;
>@@ -777,12 +778,8 @@ static void free_section_usemap(struct page *memmap, unsigned long *usemap)
> 	 * on the section which has pgdat at boot time. Just keep it as is now.
> 	 */
>
>-	if (memmap) {
>-		nr_pages = PAGE_ALIGN(PAGES_PER_SECTION * sizeof(struct page))
>-			>> PAGE_SHIFT;
>-
>-		free_map_bootmem(memmap, nr_pages);
>-	}
>+	if (memmap)
>+		free_map_bootmem(memmap);
> }
>
> void sparse_remove_one_section(struct zone *zone, struct mem_section *ms)
>-- 
>1.7.1

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Re: [PATCH 2/2] mm/sparsemem: Fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

[Zhang Yanfei]

Hello wanpeng,

On 10/05/2013 01:54 PM, Wanpeng Li wrote:
> Hi Yanfei,
> On Thu, Oct 03, 2013 at 11:32:02AM +0800, Zhang Yanfei wrote:
>> From: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>>
>> We pass the number of pages which hold page structs of a memory
>> section to function free_map_bootmem. This is right when
>> !CONFIG_SPARSEMEM_VMEMMAP but wrong when CONFIG_SPARSEMEM_VMEMMAP.
>> When CONFIG_SPARSEMEM_VMEMMAP, we should pass the number of pages
>> of a memory section to free_map_bootmem.
>>
>> So the fix is removing the nr_pages parameter. When
>> CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
>> PAGES_PER_SECTION in free_map_bootmem. When !CONFIG_SPARSEMEM_VMEMMAP,
>> we calculate page numbers needed to hold the page structs for a
>> memory section and use the value in free_map_bootmem.
>>
>> Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
>> ---
>> mm/sparse.c |   17 +++++++----------
>> 1 files changed, 7 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index fbb9dbc..908c134 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -603,10 +603,10 @@ static void __kfree_section_memmap(struct page *memmap)
>> 	vmemmap_free(start, end);
>> }
>> #ifdef CONFIG_MEMORY_HOTREMOVE
>> -static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
>> +static void free_map_bootmem(struct page *memmap)
>> {
>> 	unsigned long start = (unsigned long)memmap;
>> -	unsigned long end = (unsigned long)(memmap + nr_pages);
>> +	unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
>>
>> 	vmemmap_free(start, end);
>> }
>> @@ -648,11 +648,13 @@ static void __kfree_section_memmap(struct page *memmap)
>> }
>>
>> #ifdef CONFIG_MEMORY_HOTREMOVE
>> -static void free_map_bootmem(struct page *memmap, unsigned long nr_pages)
>> +static void free_map_bootmem(struct page *memmap)
>> {
>> 	unsigned long maps_section_nr, removing_section_nr, i;
>> 	unsigned long magic;
>> 	struct page *page = virt_to_page(memmap);
>> +	unsigned long nr_pages = get_order(sizeof(struct page) *
>> +					   PAGES_PER_SECTION);
> 
> Why replace PAGE_ALIGN(XXX) >> PAGE_SHIFT by get_order(XXX)? This will result 
> in memory leak.

oops... I will correct this by sending a new version.

Thanks.


-- 
Thanks.
Zhang Yanfei

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Re: [PATCH 2/2] mm/sparsemem: Fix a bug in free_map_bootmem when CONFIG_SPARSEMEM_VMEMMAP

[Zhang Yanfei]

Hello andrew,

On 10/04/2013 04:42 AM, Andrew Morton wrote:
> On Thu, 03 Oct 2013 11:32:02 +0800 Zhang Yanfei <zhangyanfei.yes@gmail.com> wrote:
> 
>> We pass the number of pages which hold page structs of a memory
>> section to function free_map_bootmem. This is right when
>> !CONFIG_SPARSEMEM_VMEMMAP but wrong when CONFIG_SPARSEMEM_VMEMMAP.
>> When CONFIG_SPARSEMEM_VMEMMAP, we should pass the number of pages
>> of a memory section to free_map_bootmem.
>>
>> So the fix is removing the nr_pages parameter. When
>> CONFIG_SPARSEMEM_VMEMMAP, we directly use the prefined marco
>> PAGES_PER_SECTION in free_map_bootmem. When !CONFIG_SPARSEMEM_VMEMMAP,
>> we calculate page numbers needed to hold the page structs for a
>> memory section and use the value in free_map_bootmem.
> 
> What were the runtime user-visible effects of that bug?
> 
> Please always include this information when fixing a bug.


Sorry....This was found by reading the code. And I have no machine that
support memory hot-remove to test the bug now. But I believe it is a bug.

BTW, I've made a mistake in this patch which was found by wanpeng. I'll
send v2.

-- 
Thanks.
Zhang Yanfei

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