[PATCH 0/3] minor cleanups for page_ext

[PATCH 0/3] minor cleanups for page_ext

[Kemeng Shi]

Hi all, this series contains some random minor cleanups for page_ext.
More details can be found in respective patches. Thanks!

Kemeng Shi (3):
  mm/page_ext: remove unused return value of offline_page_ext
  mm/page_ext: remove rollback for untouched mem_section in
    online_page_ext
  mm/page_ext: move functions around for minor cleanups to page_ext

 mm/page_ext.c | 101 ++++++++++++++++++++++++--------------------------
 1 file changed, 48 insertions(+), 53 deletions(-)

-- 
2.30.0

[PATCH 1/3] mm/page_ext: remove unused return value of offline_page_ext

[Kemeng Shi]

offline_page_ext always returns 0 and no caller checks the return value.
Just remove unused return value of offline_page_ext.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 mm/page_ext.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index dc1626be458b..096451df1c87 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -430,7 +430,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
 	return -ENOMEM;
 }
 
-static int __meminit offline_page_ext(unsigned long start_pfn,
+static void __meminit offline_page_ext(unsigned long start_pfn,
 				unsigned long nr_pages)
 {
 	unsigned long start, end, pfn;
@@ -454,8 +454,6 @@ static int __meminit offline_page_ext(unsigned long start_pfn,
 
 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 		__free_page_ext(pfn);
-	return 0;
-
 }
 
 static int __meminit page_ext_callback(struct notifier_block *self,
-- 
2.30.0

[PATCH 2/3] mm/page_ext: remove rollback for untouched mem_section in online_page_ext

[Kemeng Shi]

If init_section_page_ext failed, we only need rollback for mem_section
before failed mem_section. Make rollback end point to failed mem_section
to remove unnecessary rollback.

As pfn += PAGES_PER_SECTION will be executed even if init_section_page_ext
failed. So pfn points to mem_section after failed mem_section. Subtract
one mem_section from pfn to get failed mem_section.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 mm/page_ext.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index 096451df1c87..f052397dc70f 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -424,6 +424,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
 		return 0;
 
 	/* rollback */
+	end = pfn - PAGES_PER_SECTION;
 	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
 		__free_page_ext(pfn);
 
-- 
2.30.0

[PATCH 3/3] mm/page_ext: move functions around for minor cleanups to page_ext

[Kemeng Shi]

1. move page_ext_get and page_ext_put down to remove forward declaration
of lookup_page_ext.
2. move page_ext_init_flatmem_late down to existing non SPARS block
to remove a new non SPARS block and to keep code for non SPARS tight.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
---
 mm/page_ext.c | 96 ++++++++++++++++++++++++---------------------------
 1 file changed, 46 insertions(+), 50 deletions(-)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index f052397dc70f..4548fcc66d74 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -90,7 +90,6 @@ static struct page_ext_operations *page_ext_ops[] __initdata = {
 unsigned long page_ext_size;
 
 static unsigned long total_usage;
-static struct page_ext *lookup_page_ext(const struct page *page);
 
 bool early_page_ext __meminitdata;
 static int __init setup_early_page_ext(char *str)
@@ -137,62 +136,16 @@ static void __init invoke_init_callbacks(void)
 	}
 }
 
-#ifndef CONFIG_SPARSEMEM
-void __init page_ext_init_flatmem_late(void)
-{
-	invoke_init_callbacks();
-}
-#endif
-
 static inline struct page_ext *get_entry(void *base, unsigned long index)
 {
 	return base + page_ext_size * index;
 }
 
-/**
- * page_ext_get() - Get the extended information for a page.
- * @page: The page we're interested in.
- *
- * Ensures that the page_ext will remain valid until page_ext_put()
- * is called.
- *
- * Return: NULL if no page_ext exists for this page.
- * Context: Any context.  Caller may not sleep until they have called
- * page_ext_put().
- */
-struct page_ext *page_ext_get(struct page *page)
-{
-	struct page_ext *page_ext;
-
-	rcu_read_lock();
-	page_ext = lookup_page_ext(page);
-	if (!page_ext) {
-		rcu_read_unlock();
-		return NULL;
-	}
-
-	return page_ext;
-}
-
-/**
- * page_ext_put() - Working with page extended information is done.
- * @page_ext: Page extended information received from page_ext_get().
- *
- * The page extended information of the page may not be valid after this
- * function is called.
- *
- * Return: None.
- * Context: Any context with corresponding page_ext_get() is called.
- */
-void page_ext_put(struct page_ext *page_ext)
+#ifndef CONFIG_SPARSEMEM
+void __init page_ext_init_flatmem_late(void)
 {
-	if (unlikely(!page_ext))
-		return;
-
-	rcu_read_unlock();
+	invoke_init_callbacks();
 }
-#ifndef CONFIG_SPARSEMEM
-
 
 void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 {
@@ -536,3 +489,46 @@ void __meminit pgdat_page_ext_init(struct pglist_data *pgdat)
 }
 
 #endif
+
+/**
+ * page_ext_get() - Get the extended information for a page.
+ * @page: The page we're interested in.
+ *
+ * Ensures that the page_ext will remain valid until page_ext_put()
+ * is called.
+ *
+ * Return: NULL if no page_ext exists for this page.
+ * Context: Any context.  Caller may not sleep until they have called
+ * page_ext_put().
+ */
+struct page_ext *page_ext_get(struct page *page)
+{
+	struct page_ext *page_ext;
+
+	rcu_read_lock();
+	page_ext = lookup_page_ext(page);
+	if (!page_ext) {
+		rcu_read_unlock();
+		return NULL;
+	}
+
+	return page_ext;
+}
+
+/**
+ * page_ext_put() - Working with page extended information is done.
+ * @page_ext: Page extended information received from page_ext_get().
+ *
+ * The page extended information of the page may not be valid after this
+ * function is called.
+ *
+ * Return: None.
+ * Context: Any context with corresponding page_ext_get() is called.
+ */
+void page_ext_put(struct page_ext *page_ext)
+{
+	if (unlikely(!page_ext))
+		return;
+
+	rcu_read_unlock();
+}
-- 
2.30.0

Re: [PATCH 2/3] mm/page_ext: remove rollback for untouched mem_section in online_page_ext

[Andrew Morton]

On Fri, 14 Jul 2023 19:47:48 +0800 Kemeng Shi <shikemeng@huaweicloud.com> wrote:

> If init_section_page_ext failed, we only need rollback for mem_section
> before failed mem_section. Make rollback end point to failed mem_section
> to remove unnecessary rollback.
> 
> As pfn += PAGES_PER_SECTION will be executed even if init_section_page_ext
> failed. So pfn points to mem_section after failed mem_section. Subtract
> one mem_section from pfn to get failed mem_section.
> 
> ...
>
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -424,6 +424,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
>  		return 0;
>  
>  	/* rollback */
> +	end = pfn - PAGES_PER_SECTION;
>  	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
>  		__free_page_ext(pfn);
>  

This is a bugfix, yes?

I guess init_section_page_ext() never fails for anyone...

Re: [PATCH 2/3] mm/page_ext: remove rollback for untouched mem_section in online_page_ext

[Kemeng Shi]

on 7/15/2023 1:54 AM, Andrew Morton wrote:
> On Fri, 14 Jul 2023 19:47:48 +0800 Kemeng Shi <shikemeng@huaweicloud.com> wrote:
> 
>> If init_section_page_ext failed, we only need rollback for mem_section
>> before failed mem_section. Make rollback end point to failed mem_section
>> to remove unnecessary rollback.
>>
>> As pfn += PAGES_PER_SECTION will be executed even if init_section_page_ext
>> failed. So pfn points to mem_section after failed mem_section. Subtract
>> one mem_section from pfn to get failed mem_section.
>>
>> ...
>>
>> --- a/mm/page_ext.c
>> +++ b/mm/page_ext.c
>> @@ -424,6 +424,7 @@ static int __meminit online_page_ext(unsigned long start_pfn,
>>  		return 0;
>>  
>>  	/* rollback */
>> +	end = pfn - PAGES_PER_SECTION;
>>  	for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION)
>>  		__free_page_ext(pfn);
>>  
> 
> This is a bugfix, yes?
> 
> I guess init_section_page_ext() never fails for anyone...
I marked this as cleanup because __free_page_ext can handle NULL page_ext
from uninitialized mem_section. Then no real bug will be triggered even
if init_section_page_ext failed.
-- 
Best wishes
Kemeng Shi