linux-kernel - Re: [PATCH v2 3/5] kernel/power: allow hibernation with page

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Date:   Thu, 12 Nov 2020 15:39:05 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Alexander Potapenko <glider@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mateusz Nosek <mateusznosek0@...il.com>,
        Laura Abbott <labbott@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v2 3/5] kernel/power: allow hibernation with page_poison
 sanity checking

On 11/11/20 4:42 PM, David Hildenbrand wrote:
...
>> @@ -1152,12 +1152,18 @@ void clear_free_pages(void)
>>   	if (WARN_ON(!(free_pages_map)))
>>   		return;
>>   
>> -	if (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) || want_init_on_free()) {
>> +	if (page_poisoning_enabled() || want_init_on_free()) {
>>   		memory_bm_position_reset(bm);
>>   		pfn = memory_bm_next_pfn(bm);
>>   		while (pfn != BM_END_OF_MAP) {
>> -			if (pfn_valid(pfn))
>> -				clear_highpage(pfn_to_page(pfn));
>> +			if (pfn_valid(pfn)) {
>> +				struct page *page = pfn_to_page(pfn);
> 
> ^ empty line missing. And at least I prefer to declare all variables in
> the function header.
> 
> I'd even suggest to move this into a separate function like
> 
> clear_or_poison_free_page(struct page *page)
> 
> 

Ok, fixup below.

----8<----
 From cae1e8ccfa57c28ed1b2f5f8a47319b86cbdcfbf Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Thu, 12 Nov 2020 15:33:07 +0100
Subject: [PATCH] kernel/power: allow hibernation with page_poison sanity
  checking-fix

Adapt to __kernel_unpoison_pages fixup. Split out clear_or_poison_free_page()
per David Hildenbrand.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
  include/linux/mm.h      |  1 +
  kernel/power/snapshot.c | 18 ++++++++++--------
  2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 861b9392b5dc..d4cfb06a611e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2896,6 +2896,7 @@ static inline void kernel_unpoison_pages(struct page *page, int numpages)
  #else
  static inline bool page_poisoning_enabled(void) { return false; }
  static inline bool page_poisoning_enabled_static(void) { return false; }
+static inline void __kernel_poison_pages(struct page *page, int nunmpages) { }
  static inline void kernel_poison_pages(struct page *page, int numpages) { }
  static inline void kernel_unpoison_pages(struct page *page, int numpages) { }
  #endif
diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 6b1c84afa891..a3491b29c5cc 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1144,6 +1144,14 @@ void free_basic_memory_bitmaps(void)
  	pr_debug("Basic memory bitmaps freed\n");
  }
  
+static void clear_or_poison_free_page(struct page *page)
+{
+	if (page_poisoning_enabled_static())
+		__kernel_poison_pages(page, 1);
+	else if (want_init_on_free())
+		clear_highpage(page);
+}
+
  void clear_or_poison_free_pages(void)
  {
  	struct memory_bitmap *bm = free_pages_map;
@@ -1156,14 +1164,8 @@ void clear_or_poison_free_pages(void)
  		memory_bm_position_reset(bm);
  		pfn = memory_bm_next_pfn(bm);
  		while (pfn != BM_END_OF_MAP) {
-			if (pfn_valid(pfn)) {
-				struct page *page = pfn_to_page(pfn);
-				if (page_poisoning_enabled_static())
-					kernel_poison_pages(page, 1);
-				else if (want_init_on_free())
-					clear_highpage(page);
-
-			}
+			if (pfn_valid(pfn))
+				clear_or_poison_free_page(pfn_to_page(pfn));
  
  			pfn = memory_bm_next_pfn(bm);
  		}
-- 
2.29.1