[PATCH 1/3] mm/page_alloc: fix a terrible misleading comment

[PATCH 1/3] mm/page_alloc: fix a terrible misleading comment

[Yaowei Bai]

The comment says that the per-cpu batchsize and zone watermarks
are determined by present_pages which is definitely wrong, they
are both calculated from managed_pages. Fix it.

Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b5240b..c22b133 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6003,7 +6003,7 @@ void __init mem_init_print_info(const char *str)
  * set_dma_reserve - set the specified number of pages reserved in the first zone
  * @new_dma_reserve: The number of pages to mark reserved
  *
- * The per-cpu batchsize and zone watermarks are determined by present_pages.
+ * The per-cpu batchsize and zone watermarks are determined by managed_pages.
  * In the DMA zone, a significant percentage may be consumed by kernel image
  * and other unfreeable allocations which can skew the watermarks badly. This
  * function may optionally be used to account for unfreeable pages in the
-- 
1.9.1


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[PATCH 2/3] mm/page_alloc: add a helper function to check page before alloc/free

[Yaowei Bai]

The major portion of check_new_page() and free_pages_check() are same,
introduce a helper function check_one_page() for readablity.

Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
---
 mm/page_alloc.c | 54 +++++++++++++++++++++++-------------------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c22b133..a0839de 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -707,7 +707,7 @@ out:
 	zone->free_area[order].nr_free++;
 }
 
-static inline int free_pages_check(struct page *page)
+static inline int check_one_page(struct page *page, bool free)
 {
 	const char *bad_reason = NULL;
 	unsigned long bad_flags = 0;
@@ -718,10 +718,16 @@ static inline int free_pages_check(struct page *page)
 		bad_reason = "non-NULL mapping";
 	if (unlikely(atomic_read(&page->_count) != 0))
 		bad_reason = "nonzero _count";
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
-		bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
-		bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
-	}
+	if (free)
+		if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
+			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
+			bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
+		}
+	else
+		if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
+			bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
+			bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
+		}
 #ifdef CONFIG_MEMCG
 	if (unlikely(page->mem_cgroup))
 		bad_reason = "page still charged to cgroup";
@@ -730,6 +736,17 @@ static inline int free_pages_check(struct page *page)
 		bad_page(page, bad_reason, bad_flags);
 		return 1;
 	}
+	return 0;
+}
+
+static inline int free_pages_check(struct page *page)
+{
+	int ret=0;
+
+	ret=check_one_page(page, true);
+	if (ret)
+		return ret;
+
 	page_cpupid_reset_last(page);
 	if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
 		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
@@ -1287,32 +1304,7 @@ static inline void expand(struct zone *zone, struct page *page,
  */
 static inline int check_new_page(struct page *page)
 {
-	const char *bad_reason = NULL;
-	unsigned long bad_flags = 0;
-
-	if (unlikely(page_mapcount(page)))
-		bad_reason = "nonzero mapcount";
-	if (unlikely(page->mapping != NULL))
-		bad_reason = "non-NULL mapping";
-	if (unlikely(atomic_read(&page->_count) != 0))
-		bad_reason = "nonzero _count";
-	if (unlikely(page->flags & __PG_HWPOISON)) {
-		bad_reason = "HWPoisoned (hardware-corrupted)";
-		bad_flags = __PG_HWPOISON;
-	}
-	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
-		bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
-		bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
-	}
-#ifdef CONFIG_MEMCG
-	if (unlikely(page->mem_cgroup))
-		bad_reason = "page still charged to cgroup";
-#endif
-	if (unlikely(bad_reason)) {
-		bad_page(page, bad_reason, bad_flags);
-		return 1;
-	}
-	return 0;
+	return check_one_page(page, false);
 }
 
 static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
-- 
1.9.1


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Re: [PATCH 2/3] mm/page_alloc: add a helper function to check page before alloc/free

[Michal Hocko]

On Sat 22-08-15 15:40:11, Yaowei Bai wrote:
> The major portion of check_new_page() and free_pages_check() are same,
> introduce a helper function check_one_page() for readablity.
> 
> Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
> ---
>  mm/page_alloc.c | 54 +++++++++++++++++++++++-------------------------------
>  1 file changed, 23 insertions(+), 31 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index c22b133..a0839de 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -707,7 +707,7 @@ out:
>  	zone->free_area[order].nr_free++;
>  }
>  
> -static inline int free_pages_check(struct page *page)
> +static inline int check_one_page(struct page *page, bool free)
>  {
>  	const char *bad_reason = NULL;
>  	unsigned long bad_flags = 0;
> @@ -718,10 +718,16 @@ static inline int free_pages_check(struct page *page)
>  		bad_reason = "non-NULL mapping";
>  	if (unlikely(atomic_read(&page->_count) != 0))
>  		bad_reason = "nonzero _count";
> -	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
> -		bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
> -		bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
> -	}
> +	if (free)
> +		if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_FREE)) {
> +			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
> +			bad_flags = PAGE_FLAGS_CHECK_AT_FREE;
> +		}
> +	else
> +		if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
> +			bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
> +			bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
> +		}

Wouldn't it be easier to simply give bad_flags as another parameter?

>  #ifdef CONFIG_MEMCG
>  	if (unlikely(page->mem_cgroup))
>  		bad_reason = "page still charged to cgroup";
> @@ -730,6 +736,17 @@ static inline int free_pages_check(struct page *page)
>  		bad_page(page, bad_reason, bad_flags);
>  		return 1;
>  	}
> +	return 0;
> +}
> +
> +static inline int free_pages_check(struct page *page)
> +{
> +	int ret=0;
> +
> +	ret=check_one_page(page, true);
> +	if (ret)
> +		return ret;
> +
>  	page_cpupid_reset_last(page);
>  	if (page->flags & PAGE_FLAGS_CHECK_AT_PREP)
>  		page->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
> @@ -1287,32 +1304,7 @@ static inline void expand(struct zone *zone, struct page *page,
>   */
>  static inline int check_new_page(struct page *page)
>  {
> -	const char *bad_reason = NULL;
> -	unsigned long bad_flags = 0;
> -
> -	if (unlikely(page_mapcount(page)))
> -		bad_reason = "nonzero mapcount";
> -	if (unlikely(page->mapping != NULL))
> -		bad_reason = "non-NULL mapping";
> -	if (unlikely(atomic_read(&page->_count) != 0))
> -		bad_reason = "nonzero _count";
> -	if (unlikely(page->flags & __PG_HWPOISON)) {
> -		bad_reason = "HWPoisoned (hardware-corrupted)";
> -		bad_flags = __PG_HWPOISON;
> -	}
> -	if (unlikely(page->flags & PAGE_FLAGS_CHECK_AT_PREP)) {
> -		bad_reason = "PAGE_FLAGS_CHECK_AT_PREP flag set";
> -		bad_flags = PAGE_FLAGS_CHECK_AT_PREP;
> -	}
> -#ifdef CONFIG_MEMCG
> -	if (unlikely(page->mem_cgroup))
> -		bad_reason = "page still charged to cgroup";
> -#endif
> -	if (unlikely(bad_reason)) {
> -		bad_page(page, bad_reason, bad_flags);
> -		return 1;
> -	}
> -	return 0;
> +	return check_one_page(page, false);
>  }
>  
>  static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
> -- 
> 1.9.1
> 
> 
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-- 
Michal Hocko
SUSE Labs

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[PATCH 3/3] mm/memblock: fix memblock comment

[Yaowei Bai]

's/amd/and/'

Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
---
 include/linux/memblock.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index cc4b019..273aad7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -304,7 +304,7 @@ static inline void __init memblock_set_bottom_up(bool enable) {}
 static inline bool memblock_bottom_up(void) { return false; }
 #endif
 
-/* Flags for memblock_alloc_base() amd __memblock_alloc_base() */
+/* Flags for memblock_alloc_base() and __memblock_alloc_base() */
 #define MEMBLOCK_ALLOC_ANYWHERE	(~(phys_addr_t)0)
 #define MEMBLOCK_ALLOC_ACCESSIBLE	0
 
-- 
1.9.1


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Re: [PATCH 3/3] mm/memblock: fix memblock comment

[Michal Hocko]

On Sat 22-08-15 15:40:12, Yaowei Bai wrote:
> 's/amd/and/'

Is this really worth it? It doesn't help grepability and just churns the
history.

> 
> Signed-off-by: Yaowei Bai <bywxiaobai@163.com>
> ---
>  include/linux/memblock.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index cc4b019..273aad7 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -304,7 +304,7 @@ static inline void __init memblock_set_bottom_up(bool enable) {}
>  static inline bool memblock_bottom_up(void) { return false; }
>  #endif
>  
> -/* Flags for memblock_alloc_base() amd __memblock_alloc_base() */
> +/* Flags for memblock_alloc_base() and __memblock_alloc_base() */
>  #define MEMBLOCK_ALLOC_ANYWHERE	(~(phys_addr_t)0)
>  #define MEMBLOCK_ALLOC_ACCESSIBLE	0
>  
> -- 
> 1.9.1
> 
> 
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-- 
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SUSE Labs

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Re: [PATCH 1/3] mm/page_alloc: fix a terrible misleading comment

[Michal Hocko]

On Sat 22-08-15 15:40:10, Yaowei Bai wrote:
> The comment says that the per-cpu batchsize and zone watermarks
> are determined by present_pages which is definitely wrong, they
> are both calculated from managed_pages. Fix it.

This seems to be missed in b40da04946aa ("mm: use zone->present_pages
instead of zone->managed_pages where appropriate")
> 
> Signed-off-by: Yaowei Bai <bywxiaobai@163.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5b5240b..c22b133 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6003,7 +6003,7 @@ void __init mem_init_print_info(const char *str)
>   * set_dma_reserve - set the specified number of pages reserved in the first zone
>   * @new_dma_reserve: The number of pages to mark reserved
>   *
> - * The per-cpu batchsize and zone watermarks are determined by present_pages.
> + * The per-cpu batchsize and zone watermarks are determined by managed_pages.
>   * In the DMA zone, a significant percentage may be consumed by kernel image
>   * and other unfreeable allocations which can skew the watermarks badly. This
>   * function may optionally be used to account for unfreeable pages in the
> -- 
> 1.9.1
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/

-- 
Michal Hocko
SUSE Labs

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