Re: [RFC v3 3/4] mm, printk: introduce new format %pGt for page_type

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Sun, Dec 18, 2022 at 07:19:00PM +0900, Hyeonggon Yoo wrote:
> %pGp format is used to print 'flags' field of struct page.
> As some page flags (e.g. PG_buddy, see page-flags.h for more details)
> are set in page_type field, introduce %pGt format which provides
> human readable output of page_type.
> 
> Note that the sense of bits are different in page_type. if page_type is
> 0xffffffff, no flags are set. if PG_slab (0x00100000) flag is set,
> page_type is 0xffefffff. Clearing a bit means we set the bit.
> 
> Bits in page_type are inverted when printing page type names.

...

> +#define __def_pagetype_names						\
> +	{PG_slab,			"slab"		},		\
> +	{PG_offline,			"offline"	},		\
> +	{PG_guard,			"guard"		},		\
> +	{PG_table,			"table"		},		\
> +	{PG_buddy,			"buddy"		}

Wondering if it will be more robust to define a helper macro

#define DEF_PAGETYPE_NAME(_name)	{ PG_##_name, __stringify(_name) }
...
#undef DEF_PAGETYPE_MASK

In this case it decreases the chances of typo in the strings and flags.

-- 
With Best Regards,
Andy Shevchenko