Re: [PATCH] mm: Improve dump_page() for compound pages

[John Hubbard <jhubbard@nvidia.com>]

On 2/7/20 8:48 PM, Matthew Wilcox wrote:
> On Fri, Feb 07, 2020 at 08:44:15PM -0800, Matthew Wilcox wrote:
>> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>>
>> There was no protection against a corrupted struct page having an
>> implausible compound_head().  Sanity check that a compound page has
>> a head within reach of the maximum allocatable page (this will need
>> to be adjusted if one of the plans to allocate 1GB pages comes to
>> fruition).  In addition,
>>
>>  - Print the mapping pointer using %p insted of %px.  The actual value of
>>    the pointer can be read out of the raw page dump and using %p gives a
>>    chance to correlate it with an earlier printk of the mapping pointer
>>  - Print the mapping pointer from the head page, not the tail page
>>    (the tail ->mapping pointer may be in use for other purposes, eg part
>>    of a list_head)
>>  - Print the order of the page for compound pages
>>  - Dump the raw head page as well as the raw page
>>  - Print the refcount from the head page, not the tail page
>>
>> Suggested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
>> Co-developed-by: John Hubbard <jhubbard@nvidia.com>
>> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> 
> John, in comparison to the patch I sent earlier today, this version changes:
> 
>  - Reorder the things printed in the compound case so that all the information
>    which is printed for non-compound pages is printed first
>  - Removed inconsistent space between "compound_mapcount:" and the value
>  - Print the refcount of the head page instead of the tail (which was the
>    point of your patch!)
>  - Print the mapping of the head instead of the tail
>  - Don't dump the raw head if the page passed in was the head page
> 

Got it, I've snarfed it into my series, thanks very much!


thanks,
-- 
John Hubbard
NVIDIA