Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Minchan Kim <minchan@kernel.org>
To: Yang Shi <yang.shi@linaro.org>
Cc: akpm@linux-foundation.org, iamjoonsoo.kim@lge.com,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linaro-kernel@lists.linaro.org
Subject: Re: [PATCH] mm: check the return value of lookup_page_ext for all call sites
Date: Mon, 30 May 2016 15:17:53 +0900
Message-ID: <20160530061753.GC28624@bbox> (raw)
In-Reply-To: <1464023768-31025-1-git-send-email-yang.shi@linaro.org>

On Mon, May 23, 2016 at 10:16:08AM -0700, Yang Shi wrote:
> Per the discussion with Joonsoo Kim [1], we need check the return value of
> lookup_page_ext() for all call sites since it might return NULL in some cases,
> although it is unlikely, i.e. memory hotplug.
> 
> Tested with ltp with "page_owner=0".
> 
> [1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE
> 
> Signed-off-by: Yang Shi <yang.shi@linaro.org>
> ---
>  include/linux/page_idle.h | 43 ++++++++++++++++++++++++++++++++++++-------
>  mm/page_alloc.c           |  6 ++++++
>  mm/page_owner.c           | 27 +++++++++++++++++++++++++++
>  mm/page_poison.c          |  8 +++++++-
>  mm/vmstat.c               |  2 ++
>  5 files changed, 78 insertions(+), 8 deletions(-)
> 
> diff --git a/include/linux/page_idle.h b/include/linux/page_idle.h
> index bf268fa..8f5d4ad 100644
> --- a/include/linux/page_idle.h
> +++ b/include/linux/page_idle.h
> @@ -46,33 +46,62 @@ extern struct page_ext_operations page_idle_ops;
>  
>  static inline bool page_is_young(struct page *page)
>  {
> -	return test_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return false;
> +
> +	return test_bit(PAGE_EXT_YOUNG, &page_ext->flags);
>  }
>  
>  static inline void set_page_young(struct page *page)
>  {
> -	set_bit(PAGE_EXT_YOUNG, &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return;
> +
> +	set_bit(PAGE_EXT_YOUNG, &page_ext->flags);
>  }
>  
>  static inline bool test_and_clear_page_young(struct page *page)
>  {
> -	return test_and_clear_bit(PAGE_EXT_YOUNG,
> -				  &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return false;
> +
> +	return test_and_clear_bit(PAGE_EXT_YOUNG, &page_ext->flags);
>  }
>  
>  static inline bool page_is_idle(struct page *page)
>  {
> -	return test_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return false;
> +
> +	return test_bit(PAGE_EXT_IDLE, &page_ext->flags);
>  }
>  
>  static inline void set_page_idle(struct page *page)
>  {
> -	set_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return;
> +
> +	set_bit(PAGE_EXT_IDLE, &page_ext->flags);
>  }
>  
>  static inline void clear_page_idle(struct page *page)
>  {
> -	clear_bit(PAGE_EXT_IDLE, &lookup_page_ext(page)->flags);
> +	struct page_ext *page_ext;
> +	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)
> +		return;
> +
> +	clear_bit(PAGE_EXT_IDLE, &page_ext->flags);
>  }
>  #endif /* CONFIG_64BIT */
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f8f3bfc..d27e8b9 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -656,6 +656,9 @@ static inline void set_page_guard(struct zone *zone, struct page *page,
>  		return;
>  
>  	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		return;
> +
>  	__set_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
>  
>  	INIT_LIST_HEAD(&page->lru);
> @@ -673,6 +676,9 @@ static inline void clear_page_guard(struct zone *zone, struct page *page,
>  		return;
>  
>  	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		return;
> +
>  	__clear_bit(PAGE_EXT_DEBUG_GUARD, &page_ext->flags);
>  
>  	set_page_private(page, 0);
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 792b56d..902e398 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -55,6 +55,8 @@ void __reset_page_owner(struct page *page, unsigned int order)
>  
>  	for (i = 0; i < (1 << order); i++) {
>  		page_ext = lookup_page_ext(page + i);
> +		if (unlikely(!page_ext))
> +			continue;
>  		__clear_bit(PAGE_EXT_OWNER, &page_ext->flags);
>  	}
>  }
> @@ -62,6 +64,10 @@ void __reset_page_owner(struct page *page, unsigned int order)
>  void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
>  {
>  	struct page_ext *page_ext = lookup_page_ext(page);
> +
> +	if (unlikely(!page_ext))
> +		return;
> +
>  	struct stack_trace trace = {
>  		.nr_entries = 0,
>  		.max_entries = ARRAY_SIZE(page_ext->trace_entries),
> @@ -82,6 +88,8 @@ void __set_page_owner(struct page *page, unsigned int order, gfp_t gfp_mask)
>  void __set_page_owner_migrate_reason(struct page *page, int reason)
>  {
>  	struct page_ext *page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		return;
>  
>  	page_ext->last_migrate_reason = reason;
>  }
> @@ -89,6 +97,12 @@ void __set_page_owner_migrate_reason(struct page *page, int reason)
>  gfp_t __get_page_owner_gfp(struct page *page)
>  {
>  	struct page_ext *page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		/*
> +		 * The caller just returns 0 if no valid gfp
> +		 * So return 0 here too.
> +		 */
> +		return 0;
>  
>  	return page_ext->gfp_mask;
>  }
> @@ -97,6 +111,10 @@ void __copy_page_owner(struct page *oldpage, struct page *newpage)
>  {
>  	struct page_ext *old_ext = lookup_page_ext(oldpage);
>  	struct page_ext *new_ext = lookup_page_ext(newpage);
> +
> +	if (unlikely(!old_ext || !new_ext))
> +		return;
> +
>  	int i;
>  
>  	new_ext->order = old_ext->order;
> @@ -186,6 +204,11 @@ err:
>  void __dump_page_owner(struct page *page)
>  {
>  	struct page_ext *page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext)) {
> +		pr_alert("There is not page extension available.\n");
> +		return;
> +	}
> +
>  	struct stack_trace trace = {
>  		.nr_entries = page_ext->nr_entries,
>  		.entries = &page_ext->trace_entries[0],
> @@ -251,6 +274,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
>  		}
>  
>  		page_ext = lookup_page_ext(page);
> +		if (unlikely(!page_ext))
> +			continue;
>  
>  		/*
>  		 * Some pages could be missed by concurrent allocation or free,
> @@ -317,6 +342,8 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
>  				continue;
>  
>  			page_ext = lookup_page_ext(page);
> +			if (unlikely(!page_ext))
> +				continue;
>  
>  			/* Maybe overraping zone */
>  			if (test_bit(PAGE_EXT_OWNER, &page_ext->flags))
> diff --git a/mm/page_poison.c b/mm/page_poison.c
> index 1eae5fa..2e647c6 100644
> --- a/mm/page_poison.c
> +++ b/mm/page_poison.c
> @@ -54,6 +54,9 @@ static inline void set_page_poison(struct page *page)
>  	struct page_ext *page_ext;
>  
>  	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		return;
> +
>  	__set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
>  }
>  
> @@ -62,6 +65,9 @@ static inline void clear_page_poison(struct page *page)
>  	struct page_ext *page_ext;
>  
>  	page_ext = lookup_page_ext(page);
> +	if (unlikely(!page_ext))
> +		return;
> +
>  	__clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
>  }
>  
> @@ -70,7 +76,7 @@ bool page_is_poisoned(struct page *page)
>  	struct page_ext *page_ext;
>  
>  	page_ext = lookup_page_ext(page);
> -	if (!page_ext)
> +	if (unlikely(!page_ext))
>  		return false;
>  
>  	return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 77e42ef..cb2a67b 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1061,6 +1061,8 @@ static void pagetypeinfo_showmixedcount_print(struct seq_file *m,
>  				continue;
>  
>  			page_ext = lookup_page_ext(page);
> +			if (unlikely(!page_ext))
> +				continue;
>  
>  			if (!test_bit(PAGE_EXT_OWNER, &page_ext->flags))
>  				continue;
> -- 

There is another race with here.


                                        init_section_page_ext
                                        < reordering >
                                        section->page_ext = base - pfn

lookup_page_ext
if (section->page_ext)
  section->page_ext + pfn
                                        base = alloc_page_ext

I guess alloc_page_ext doesn't make sure to prevent such reordering so
caller of memory allocating APIB should provide right memory barrier.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

      parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-23 17:16 Yang Shi
2016-05-24  2:58 ` Minchan Kim
2016-05-26  0:37   ` Minchan Kim
2016-05-26 23:15     ` Shi, Yang
2016-05-27  5:14       ` Minchan Kim
2016-05-27  6:08         ` Joonsoo Kim
2016-05-27  8:11           ` Minchan Kim
2016-05-27 18:16             ` Shi, Yang
2016-05-30  6:11               ` Minchan Kim
2016-06-01 20:40                 ` Shi, Yang
2016-06-02  5:00                   ` Minchan Kim
2016-06-02 23:15                     ` Shi, Yang
2016-05-30  5:39             ` Joonsoo Kim
2016-05-30  6:08               ` Minchan Kim
2016-06-01 20:52                 ` Shi, Yang
2016-05-27 20:02       ` Andrew Morton
2016-05-27 20:17         ` Shi, Yang
2016-05-27 20:30           ` Andrew Morton
2016-05-24 10:08 ` [PATCH] mm: fix build problems from lookup_page_ext Arnd Bergmann
2016-05-24 16:33   ` Shi, Yang
2016-05-25  7:12 ` [PATCH] mm: check the return value of lookup_page_ext for all call sites shakil
2016-05-30  6:17 ` Minchan Kim [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20160530061753.GC28624@bbox \
    --to=minchan@kernel.org \
    --cc=akpm@linux-foundation.org \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=linaro-kernel@lists.linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=yang.shi@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git