[v2,1/4] mm: enable dump several reasons for __dump_page()
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Message ID 20200120030415.15925-2-richardw.yang@linux.intel.com
State New
Headers show
Series
  • mm/page_alloc.c: cleanup on check page
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Commit Message

Wei Yang Jan. 20, 2020, 3:04 a.m. UTC
This is a preparation to dump all reasons during check page.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 include/linux/mmdebug.h |  2 +-
 mm/debug.c              | 11 ++++++-----
 mm/page_alloc.c         |  2 +-
 3 files changed, 8 insertions(+), 7 deletions(-)

Comments

Anshuman Khandual Jan. 20, 2020, 6:12 a.m. UTC | #1
On 01/20/2020 08:34 AM, Wei Yang wrote:
> This is a preparation to dump all reasons during check page.

This really makes sense rather then just picking the reason from
the last "if" statement.

> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
>  include/linux/mmdebug.h |  2 +-
>  mm/debug.c              | 11 ++++++-----
>  mm/page_alloc.c         |  2 +-
>  3 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
> index 2ad72d2c8cc5..f0a612db8bae 100644
> --- a/include/linux/mmdebug.h
> +++ b/include/linux/mmdebug.h
> @@ -10,7 +10,7 @@ struct vm_area_struct;
>  struct mm_struct;
>  
>  extern void dump_page(struct page *page, const char *reason);
> -extern void __dump_page(struct page *page, const char *reason);
> +extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
> --- a/mm/debug.c
> +++ b/mm/debug.c
> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
>  	{0, NULL}
>  };
>  
> -void __dump_page(struct page *page, const char *reason)
> +void __dump_page(struct page *page, int num, const char **reason)
>  {
>  	struct address_space *mapping;
>  	bool page_poisoned = PagePoisoned(page);
> -	int mapcount;
> +	int mapcount, i;
>  
>  	/*
>  	 * If struct page is poisoned don't access Page*() functions as that
> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason)
>  			sizeof(unsigned long), page,
>  			sizeof(struct page), false);
>  
> -	if (reason)
> -		pr_warn("page dumped because: %s\n", reason);
> +	pr_warn("page dumped because:\n");
> +	for (i = 0; i < num; i++)
> +		pr_warn("\t%s\n", reason[i]);

We should have a NR_BAD_PAGE_REASONS or something to cap this iteration
and also check reason[i] for non-NULL before trying to print the array.
There might be call sites like the following which will be problematic
otherwise.

split_huge_page_to_list() -> dump_page(head, NULL)

>  
>  #ifdef CONFIG_MEMCG
>  	if (!page_poisoned && page->mem_cgroup)

While here, will it be better to move the above debug print block after
mem_cgroup block instead ?

> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason)
>  
>  void dump_page(struct page *page, const char *reason)
>  {
> -	__dump_page(page, reason);
> +	__dump_page(page, 1, &reason);
>  	dump_page_owner(page);
>  }
>  EXPORT_SYMBOL(dump_page);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d047bf7d8fd4..0cf6218aaba7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason,
>  
>  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>  		current->comm, page_to_pfn(page));
> -	__dump_page(page, reason);
> +	__dump_page(page, 1, &reason);
>  	bad_flags &= page->flags;
>  	if (bad_flags)
>  		pr_alert("bad because of flags: %#lx(%pGp)\n",
> 

Do we still need to have bad_flags ? After consolidating all reasons making
a page bad should not we just print page->flags unconditionally each time and
let the user decipher it instead. __dump_page() will print page->flags for
each case (atleast after the new patch from Vlastimil). AFAICS, the only
place currently consuming bad_flags is bad_page() which seems redundant after
first calling __dump_page().
Wei Yang Jan. 20, 2020, 8:55 a.m. UTC | #2
On Mon, Jan 20, 2020 at 11:42:30AM +0530, Anshuman Khandual wrote:
>
>
>On 01/20/2020 08:34 AM, Wei Yang wrote:
>> This is a preparation to dump all reasons during check page.
>
>This really makes sense rather then just picking the reason from
>the last "if" statement.
>
>> 
>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>> ---
>>  include/linux/mmdebug.h |  2 +-
>>  mm/debug.c              | 11 ++++++-----
>>  mm/page_alloc.c         |  2 +-
>>  3 files changed, 8 insertions(+), 7 deletions(-)
>> 
>> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
>> index 2ad72d2c8cc5..f0a612db8bae 100644
>> --- a/include/linux/mmdebug.h
>> +++ b/include/linux/mmdebug.h
>> @@ -10,7 +10,7 @@ struct vm_area_struct;
>>  struct mm_struct;
>>  
>>  extern void dump_page(struct page *page, const char *reason);
>> -extern void __dump_page(struct page *page, const char *reason);
>> +extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
>> --- a/mm/debug.c
>> +++ b/mm/debug.c
>> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
>>  	{0, NULL}
>>  };
>>  
>> -void __dump_page(struct page *page, const char *reason)
>> +void __dump_page(struct page *page, int num, const char **reason)
>>  {
>>  	struct address_space *mapping;
>>  	bool page_poisoned = PagePoisoned(page);
>> -	int mapcount;
>> +	int mapcount, i;
>>  
>>  	/*
>>  	 * If struct page is poisoned don't access Page*() functions as that
>> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason)
>>  			sizeof(unsigned long), page,
>>  			sizeof(struct page), false);
>>  
>> -	if (reason)
>> -		pr_warn("page dumped because: %s\n", reason);
>> +	pr_warn("page dumped because:\n");
>> +	for (i = 0; i < num; i++)
>> +		pr_warn("\t%s\n", reason[i]);
>
>We should have a NR_BAD_PAGE_REASONS or something to cap this iteration
>and also check reason[i] for non-NULL before trying to print the array.
>There might be call sites like the following which will be problematic
>otherwise.
>
>split_huge_page_to_list() -> dump_page(head, NULL)
>

You are right, I missed this case.

>>  
>>  #ifdef CONFIG_MEMCG
>>  	if (!page_poisoned && page->mem_cgroup)
>
>While here, will it be better to move the above debug print block after
>mem_cgroup block instead ?
>

Not sure, let's see whether others have some idea.

>> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason)
>>  
>>  void dump_page(struct page *page, const char *reason)
>>  {
>> -	__dump_page(page, reason);
>> +	__dump_page(page, 1, &reason);
>>  	dump_page_owner(page);
>>  }
>>  EXPORT_SYMBOL(dump_page);
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index d047bf7d8fd4..0cf6218aaba7 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason,
>>  
>>  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>>  		current->comm, page_to_pfn(page));
>> -	__dump_page(page, reason);
>> +	__dump_page(page, 1, &reason);
>>  	bad_flags &= page->flags;
>>  	if (bad_flags)
>>  		pr_alert("bad because of flags: %#lx(%pGp)\n",
>> 
>
>Do we still need to have bad_flags ? After consolidating all reasons making
>a page bad should not we just print page->flags unconditionally each time and
>let the user decipher it instead. __dump_page() will print page->flags for
>each case (atleast after the new patch from Vlastimil). AFAICS, the only
>place currently consuming bad_flags is bad_page() which seems redundant after
>first calling __dump_page().

Hmm... I don't catch this. The work in __dump_page() seems a little different
from this one. Not sure we could remove it.
Anshuman Khandual Jan. 21, 2020, 5:20 a.m. UTC | #3
On 01/20/2020 02:25 PM, Wei Yang wrote:
> On Mon, Jan 20, 2020 at 11:42:30AM +0530, Anshuman Khandual wrote:
>>
>>
>> On 01/20/2020 08:34 AM, Wei Yang wrote:
>>> This is a preparation to dump all reasons during check page.
>>
>> This really makes sense rather then just picking the reason from
>> the last "if" statement.
>>
>>>
>>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>>> ---
>>>  include/linux/mmdebug.h |  2 +-
>>>  mm/debug.c              | 11 ++++++-----
>>>  mm/page_alloc.c         |  2 +-
>>>  3 files changed, 8 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
>>> index 2ad72d2c8cc5..f0a612db8bae 100644
>>> --- a/include/linux/mmdebug.h
>>> +++ b/include/linux/mmdebug.h
>>> @@ -10,7 +10,7 @@ struct vm_area_struct;
>>>  struct mm_struct;
>>>  
>>>  extern void dump_page(struct page *page, const char *reason);
>>> -extern void __dump_page(struct page *page, const char *reason);
>>> +extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
>>> --- a/mm/debug.c
>>> +++ b/mm/debug.c
>>> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
>>>  	{0, NULL}
>>>  };
>>>  
>>> -void __dump_page(struct page *page, const char *reason)
>>> +void __dump_page(struct page *page, int num, const char **reason)
>>>  {
>>>  	struct address_space *mapping;
>>>  	bool page_poisoned = PagePoisoned(page);
>>> -	int mapcount;
>>> +	int mapcount, i;
>>>  
>>>  	/*
>>>  	 * If struct page is poisoned don't access Page*() functions as that
>>> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason)
>>>  			sizeof(unsigned long), page,
>>>  			sizeof(struct page), false);
>>>  
>>> -	if (reason)
>>> -		pr_warn("page dumped because: %s\n", reason);
>>> +	pr_warn("page dumped because:\n");
>>> +	for (i = 0; i < num; i++)
>>> +		pr_warn("\t%s\n", reason[i]);
>>
>> We should have a NR_BAD_PAGE_REASONS or something to cap this iteration
>> and also check reason[i] for non-NULL before trying to print the array.
>> There might be call sites like the following which will be problematic
>> otherwise.
>>
>> split_huge_page_to_list() -> dump_page(head, NULL)
>>
> 
> You are right, I missed this case.
> 
>>>  
>>>  #ifdef CONFIG_MEMCG
>>>  	if (!page_poisoned && page->mem_cgroup)
>>
>> While here, will it be better to move the above debug print block after
>> mem_cgroup block instead ?
>>
> 
> Not sure, let's see whether others have some idea.
> 
>>> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason)
>>>  
>>>  void dump_page(struct page *page, const char *reason)
>>>  {
>>> -	__dump_page(page, reason);
>>> +	__dump_page(page, 1, &reason);
>>>  	dump_page_owner(page);
>>>  }
>>>  EXPORT_SYMBOL(dump_page);
>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>> index d047bf7d8fd4..0cf6218aaba7 100644
>>> --- a/mm/page_alloc.c
>>> +++ b/mm/page_alloc.c
>>> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason,
>>>  
>>>  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>>>  		current->comm, page_to_pfn(page));
>>> -	__dump_page(page, reason);
>>> +	__dump_page(page, 1, &reason);
>>>  	bad_flags &= page->flags;
>>>  	if (bad_flags)
>>>  		pr_alert("bad because of flags: %#lx(%pGp)\n",
>>>
>>
>> Do we still need to have bad_flags ? After consolidating all reasons making
>> a page bad should not we just print page->flags unconditionally each time and
>> let the user decipher it instead. __dump_page() will print page->flags for
>> each case (atleast after the new patch from Vlastimil). AFAICS, the only
>> place currently consuming bad_flags is bad_page() which seems redundant after
>> first calling __dump_page().
> 
> Hmm... I don't catch this. The work in __dump_page() seems a little different
> from this one. Not sure we could remove it.

Lets look at 'bad_flags' as it exists today without this series.

It gets evaluated in free_pages_check_bad() and check_new_page_bad() before
being passed into bad_page(). All other call sites for bad_page() just pass
0 for 'bad_flags'. Now in bad_page(), we have

        __dump_page(page, reason);
        bad_flags &= page->flags;
        if (bad_flags)
                pr_alert("bad because of flags: %#lx(%pGp)\n",
                                                bad_flags, &bad_flags);

Here, bad_flags &= page->flags will always be positive when 'reason'
is either

"PAGE_FLAGS_CHECK_AT_FREE flag(s) set"

or

"PAGE_FLAGS_CHECK_AT_PREP flag set"

The point here is we dont need to print bad_flags here as __dump_page()
already prints page->flags universally along with the "bad_reason"
after the following change.

[1] https://patchwork.kernel.org/patch/11332035/
Wei Yang Jan. 22, 2020, 12:58 a.m. UTC | #4
On Tue, Jan 21, 2020 at 10:50:41AM +0530, Anshuman Khandual wrote:
>
>
>On 01/20/2020 02:25 PM, Wei Yang wrote:
>> On Mon, Jan 20, 2020 at 11:42:30AM +0530, Anshuman Khandual wrote:
>>>
>>>
>>> On 01/20/2020 08:34 AM, Wei Yang wrote:
>>>> This is a preparation to dump all reasons during check page.
>>>
>>> This really makes sense rather then just picking the reason from
>>> the last "if" statement.
>>>
>>>>
>>>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>>>> ---
>>>>  include/linux/mmdebug.h |  2 +-
>>>>  mm/debug.c              | 11 ++++++-----
>>>>  mm/page_alloc.c         |  2 +-
>>>>  3 files changed, 8 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
>>>> index 2ad72d2c8cc5..f0a612db8bae 100644
>>>> --- a/include/linux/mmdebug.h
>>>> +++ b/include/linux/mmdebug.h
>>>> @@ -10,7 +10,7 @@ struct vm_area_struct;
>>>>  struct mm_struct;
>>>>  
>>>>  extern void dump_page(struct page *page, const char *reason);
>>>> -extern void __dump_page(struct page *page, const char *reason);
>>>> +extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
>>>> --- a/mm/debug.c
>>>> +++ b/mm/debug.c
>>>> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
>>>>  	{0, NULL}
>>>>  };
>>>>  
>>>> -void __dump_page(struct page *page, const char *reason)
>>>> +void __dump_page(struct page *page, int num, const char **reason)
>>>>  {
>>>>  	struct address_space *mapping;
>>>>  	bool page_poisoned = PagePoisoned(page);
>>>> -	int mapcount;
>>>> +	int mapcount, i;
>>>>  
>>>>  	/*
>>>>  	 * If struct page is poisoned don't access Page*() functions as that
>>>> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason)
>>>>  			sizeof(unsigned long), page,
>>>>  			sizeof(struct page), false);
>>>>  
>>>> -	if (reason)
>>>> -		pr_warn("page dumped because: %s\n", reason);
>>>> +	pr_warn("page dumped because:\n");
>>>> +	for (i = 0; i < num; i++)
>>>> +		pr_warn("\t%s\n", reason[i]);
>>>
>>> We should have a NR_BAD_PAGE_REASONS or something to cap this iteration
>>> and also check reason[i] for non-NULL before trying to print the array.
>>> There might be call sites like the following which will be problematic
>>> otherwise.
>>>
>>> split_huge_page_to_list() -> dump_page(head, NULL)
>>>
>> 
>> You are right, I missed this case.
>> 
>>>>  
>>>>  #ifdef CONFIG_MEMCG
>>>>  	if (!page_poisoned && page->mem_cgroup)
>>>
>>> While here, will it be better to move the above debug print block after
>>> mem_cgroup block instead ?
>>>
>> 
>> Not sure, let's see whether others have some idea.
>> 
>>>> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason)
>>>>  
>>>>  void dump_page(struct page *page, const char *reason)
>>>>  {
>>>> -	__dump_page(page, reason);
>>>> +	__dump_page(page, 1, &reason);
>>>>  	dump_page_owner(page);
>>>>  }
>>>>  EXPORT_SYMBOL(dump_page);
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index d047bf7d8fd4..0cf6218aaba7 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason,
>>>>  
>>>>  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>>>>  		current->comm, page_to_pfn(page));
>>>> -	__dump_page(page, reason);
>>>> +	__dump_page(page, 1, &reason);
>>>>  	bad_flags &= page->flags;
>>>>  	if (bad_flags)
>>>>  		pr_alert("bad because of flags: %#lx(%pGp)\n",
>>>>
>>>
>>> Do we still need to have bad_flags ? After consolidating all reasons making
>>> a page bad should not we just print page->flags unconditionally each time and
>>> let the user decipher it instead. __dump_page() will print page->flags for
>>> each case (atleast after the new patch from Vlastimil). AFAICS, the only
>>> place currently consuming bad_flags is bad_page() which seems redundant after
>>> first calling __dump_page().
>> 
>> Hmm... I don't catch this. The work in __dump_page() seems a little different
>> from this one. Not sure we could remove it.
>
>Lets look at 'bad_flags' as it exists today without this series.
>
>It gets evaluated in free_pages_check_bad() and check_new_page_bad() before
>being passed into bad_page(). All other call sites for bad_page() just pass
>0 for 'bad_flags'. Now in bad_page(), we have
>
>        __dump_page(page, reason);
>        bad_flags &= page->flags;
>        if (bad_flags)
>                pr_alert("bad because of flags: %#lx(%pGp)\n",
>                                                bad_flags, &bad_flags);
>
>Here, bad_flags &= page->flags will always be positive when 'reason'
>is either
>
>"PAGE_FLAGS_CHECK_AT_FREE flag(s) set"
>
>or
>
>"PAGE_FLAGS_CHECK_AT_PREP flag set"
>
>The point here is we dont need to print bad_flags here as __dump_page()
>already prints page->flags universally along with the "bad_reason"
>after the following change.
>

Thanks, I see your point. It is not necessary to print flags twice.

>[1] https://patchwork.kernel.org/patch/11332035/
Wei Yang Jan. 26, 2020, 2:44 a.m. UTC | #5
On Tue, Jan 21, 2020 at 10:50:41AM +0530, Anshuman Khandual wrote:
>
>
>On 01/20/2020 02:25 PM, Wei Yang wrote:
>> On Mon, Jan 20, 2020 at 11:42:30AM +0530, Anshuman Khandual wrote:
>>>
>>>
>>> On 01/20/2020 08:34 AM, Wei Yang wrote:
>>>> This is a preparation to dump all reasons during check page.
>>>
>>> This really makes sense rather then just picking the reason from
>>> the last "if" statement.
>>>
>>>>
>>>> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>>>> ---
>>>>  include/linux/mmdebug.h |  2 +-
>>>>  mm/debug.c              | 11 ++++++-----
>>>>  mm/page_alloc.c         |  2 +-
>>>>  3 files changed, 8 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
>>>> index 2ad72d2c8cc5..f0a612db8bae 100644
>>>> --- a/include/linux/mmdebug.h
>>>> +++ b/include/linux/mmdebug.h
>>>> @@ -10,7 +10,7 @@ struct vm_area_struct;
>>>>  struct mm_struct;
>>>>  
>>>>  extern void dump_page(struct page *page, const char *reason);
>>>> -extern void __dump_page(struct page *page, const char *reason);
>>>> +extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
>>>> --- a/mm/debug.c
>>>> +++ b/mm/debug.c
>>>> @@ -42,11 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
>>>>  	{0, NULL}
>>>>  };
>>>>  
>>>> -void __dump_page(struct page *page, const char *reason)
>>>> +void __dump_page(struct page *page, int num, const char **reason)
>>>>  {
>>>>  	struct address_space *mapping;
>>>>  	bool page_poisoned = PagePoisoned(page);
>>>> -	int mapcount;
>>>> +	int mapcount, i;
>>>>  
>>>>  	/*
>>>>  	 * If struct page is poisoned don't access Page*() functions as that
>>>> @@ -97,8 +97,9 @@ void __dump_page(struct page *page, const char *reason)
>>>>  			sizeof(unsigned long), page,
>>>>  			sizeof(struct page), false);
>>>>  
>>>> -	if (reason)
>>>> -		pr_warn("page dumped because: %s\n", reason);
>>>> +	pr_warn("page dumped because:\n");
>>>> +	for (i = 0; i < num; i++)
>>>> +		pr_warn("\t%s\n", reason[i]);
>>>
>>> We should have a NR_BAD_PAGE_REASONS or something to cap this iteration
>>> and also check reason[i] for non-NULL before trying to print the array.
>>> There might be call sites like the following which will be problematic
>>> otherwise.
>>>
>>> split_huge_page_to_list() -> dump_page(head, NULL)
>>>
>> 
>> You are right, I missed this case.
>> 
>>>>  
>>>>  #ifdef CONFIG_MEMCG
>>>>  	if (!page_poisoned && page->mem_cgroup)
>>>
>>> While here, will it be better to move the above debug print block after
>>> mem_cgroup block instead ?
>>>
>> 
>> Not sure, let's see whether others have some idea.
>> 
>>>> @@ -108,7 +109,7 @@ void __dump_page(struct page *page, const char *reason)
>>>>  
>>>>  void dump_page(struct page *page, const char *reason)
>>>>  {
>>>> -	__dump_page(page, reason);
>>>> +	__dump_page(page, 1, &reason);
>>>>  	dump_page_owner(page);
>>>>  }
>>>>  EXPORT_SYMBOL(dump_page);
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index d047bf7d8fd4..0cf6218aaba7 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -638,7 +638,7 @@ static void bad_page(struct page *page, const char *reason,
>>>>  
>>>>  	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
>>>>  		current->comm, page_to_pfn(page));
>>>> -	__dump_page(page, reason);
>>>> +	__dump_page(page, 1, &reason);
>>>>  	bad_flags &= page->flags;
>>>>  	if (bad_flags)
>>>>  		pr_alert("bad because of flags: %#lx(%pGp)\n",
>>>>
>>>
>>> Do we still need to have bad_flags ? After consolidating all reasons making
>>> a page bad should not we just print page->flags unconditionally each time and
>>> let the user decipher it instead. __dump_page() will print page->flags for
>>> each case (atleast after the new patch from Vlastimil). AFAICS, the only
>>> place currently consuming bad_flags is bad_page() which seems redundant after
>>> first calling __dump_page().
>> 
>> Hmm... I don't catch this. The work in __dump_page() seems a little different
>> from this one. Not sure we could remove it.
>
>Lets look at 'bad_flags' as it exists today without this series.
>
>It gets evaluated in free_pages_check_bad() and check_new_page_bad() before
>being passed into bad_page(). All other call sites for bad_page() just pass
>0 for 'bad_flags'. Now in bad_page(), we have
>
>        __dump_page(page, reason);
>        bad_flags &= page->flags;
>        if (bad_flags)
>                pr_alert("bad because of flags: %#lx(%pGp)\n",
>                                                bad_flags, &bad_flags);
>
>Here, bad_flags &= page->flags will always be positive when 'reason'
>is either
>
>"PAGE_FLAGS_CHECK_AT_FREE flag(s) set"
>
>or
>
>"PAGE_FLAGS_CHECK_AT_PREP flag set"
>
>The point here is we dont need to print bad_flags here as __dump_page()
>already prints page->flags universally along with the "bad_reason"
>after the following change.
>
>[1] https://patchwork.kernel.org/patch/11332035/

Hi, Anshuman

I am preparing a patch to remove the bad_flags. While since the above change
is not merged upstream yet, how can I wording the change log to point this
change?

Or I should wait till this one is merged?

Patch
diff mbox series

diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 2ad72d2c8cc5..f0a612db8bae 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -10,7 +10,7 @@  struct vm_area_struct;
 struct mm_struct;
 
 extern void dump_page(struct page *page, const char *reason);
-extern void __dump_page(struct page *page, const char *reason);
+extern void __dump_page(struct page *page, int num, 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 0461df1207cb..a8ac6f951f9f 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -42,11 +42,11 @@  const struct trace_print_flags vmaflag_names[] = {
 	{0, NULL}
 };
 
-void __dump_page(struct page *page, const char *reason)
+void __dump_page(struct page *page, int num, const char **reason)
 {
 	struct address_space *mapping;
 	bool page_poisoned = PagePoisoned(page);
-	int mapcount;
+	int mapcount, i;
 
 	/*
 	 * If struct page is poisoned don't access Page*() functions as that
@@ -97,8 +97,9 @@  void __dump_page(struct page *page, const char *reason)
 			sizeof(unsigned long), page,
 			sizeof(struct page), false);
 
-	if (reason)
-		pr_warn("page dumped because: %s\n", reason);
+	pr_warn("page dumped because:\n");
+	for (i = 0; i < num; i++)
+		pr_warn("\t%s\n", reason[i]);
 
 #ifdef CONFIG_MEMCG
 	if (!page_poisoned && page->mem_cgroup)
@@ -108,7 +109,7 @@  void __dump_page(struct page *page, const char *reason)
 
 void dump_page(struct page *page, const char *reason)
 {
-	__dump_page(page, reason);
+	__dump_page(page, 1, &reason);
 	dump_page_owner(page);
 }
 EXPORT_SYMBOL(dump_page);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d047bf7d8fd4..0cf6218aaba7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -638,7 +638,7 @@  static void bad_page(struct page *page, const char *reason,
 
 	pr_alert("BUG: Bad page state in process %s  pfn:%05lx\n",
 		current->comm, page_to_pfn(page));
-	__dump_page(page, reason);
+	__dump_page(page, 1, &reason);
 	bad_flags &= page->flags;
 	if (bad_flags)
 		pr_alert("bad because of flags: %#lx(%pGp)\n",