linux-kernel - Re: [PATCH v3 14/14] mm, debug: move bad flags printing to bad

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Message-ID: <20160107131000.GM27868@dhcp22.suse.cz>
Date:	Thu, 7 Jan 2016 14:10:00 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <iamjoonsoo.kim@....com>,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v3 14/14] mm, debug: move bad flags printing to bad_page()

On Fri 18-12-15 10:03:26, Vlastimil Babka wrote:
> Since bad_page() is the only user of the badflags parameter of
> dump_page_badflags(), we can move the code to bad_page() and simplify a bit.
> 
> The dump_page_badflags() function is renamed to __dump_page() and can still be
> called separately from dump_page() for temporary debug prints where page_owner
> info is not desired.
> 
> The only user-visible change is that page->mem_cgroup is printed before the bad
> flags.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Minchan Kim <minchan@...nel.org>
> Cc: Sasha Levin <sasha.levin@...cle.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Michal Hocko <mhocko@...e.cz>

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

> ---
>  include/linux/mmdebug.h |  3 +--
>  mm/debug.c              | 10 +++-------
>  mm/page_alloc.c         | 10 +++++++---
>  3 files changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
> index 2c8286cf162e..9b0dc2161f7a 100644
> --- a/include/linux/mmdebug.h
> +++ b/include/linux/mmdebug.h
> @@ -14,8 +14,7 @@ extern const struct trace_print_flags vmaflag_names[];
>  extern const struct trace_print_flags gfpflag_names[];
>  
>  extern void dump_page(struct page *page, const char *reason);
> -extern void dump_page_badflags(struct page *page, const char *reason,
> -			       unsigned long badflags);
> +extern void __dump_page(struct page *page, const char *reason);
>  void dump_vma(const struct vm_area_struct *vma);
>  void dump_mm(const struct mm_struct *mm);
>  
> diff --git a/mm/debug.c b/mm/debug.c
> index 7260644d8cc1..4c03b6d07c82 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -40,8 +40,7 @@ const struct trace_print_flags vmaflag_names[] = {
>  	{0, NULL}
>  };
>  
> -void dump_page_badflags(struct page *page, const char *reason,
> -		unsigned long badflags)
> +void __dump_page(struct page *page, const char *reason)
>  {
>  	pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
>  		  page, atomic_read(&page->_count), page_mapcount(page),
> @@ -50,15 +49,12 @@ void dump_page_badflags(struct page *page, const char *reason,
>  		pr_cont(" compound_mapcount: %d", compound_mapcount(page));
>  	pr_cont("\n");
>  	BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1);
> +
>  	pr_emerg("flags: %#lx(%pgp)\n", page->flags, &page->flags);
>  
>  	if (reason)
>  		pr_alert("page dumped because: %s\n", reason);
>  
> -	badflags &= page->flags;
> -	if (badflags)
> -		pr_alert("bad because of flags: %#lx(%pgp)\n", badflags,
> -								&badflags);
>  #ifdef CONFIG_MEMCG
>  	if (page->mem_cgroup)
>  		pr_alert("page->mem_cgroup:%p\n", page->mem_cgroup);
> @@ -67,7 +63,7 @@ void dump_page_badflags(struct page *page, const char *reason,
>  
>  void dump_page(struct page *page, const char *reason)
>  {
> -	dump_page_badflags(page, reason, 0);
> +	__dump_page(page, reason);
>  	dump_page_owner(page);
>  }
>  EXPORT_SYMBOL(dump_page);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 7718ee40726a..bac8842d4fcf 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -428,7 +428,7 @@ static void bad_page(struct page *page, const char *reason,
>  			goto out;
>  		}
>  		if (nr_unshown) {
> -			printk(KERN_ALERT
> +			pr_alert(
>  			      "BUG: Bad page state: %lu messages suppressed\n",
>  				nr_unshown);
>  			nr_unshown = 0;
> @@ -438,9 +438,13 @@ static void bad_page(struct page *page, const char *reason,
>  	if (nr_shown++ == 0)
>  		resume = jiffies + 60 * HZ;
>  
> -	printk(KERN_ALERT "BUG: Bad page state in process %s  pfn:%05lx\n",
> +	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>  		current->comm, page_to_pfn(page));
> -	dump_page_badflags(page, reason, bad_flags);
> +	__dump_page(page, reason);
> +	bad_flags &= page->flags;
> +	if (bad_flags)
> +		pr_alert("bad because of flags: %#lx(%pgp)\n",
> +						bad_flags, &bad_flags);
>  	dump_page_owner(page);
>  
>  	print_modules();
> -- 
> 2.6.3

-- 
Michal Hocko
SUSE Labs
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