This is a preparation to dump all reasons during check page.
Signed-off-by: Wei Yang <[email protected]>
---
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]);
#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",
--
2.17.1
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 <[email protected]>
> ---
> 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().
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 <[email protected]>
>> ---
>> 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.
--
Wei Yang
Help you, Help me
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 <[email protected]>
>>> ---
>>> 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/
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 <[email protected]>
>>>> ---
>>>> 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
Help you, Help me
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 <[email protected]>
>>>> ---
>>>> 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?
--
Wei Yang
Help you, Help me