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

Randy Dunlap
2022-12-19T19:36:05Z

On 12/19/22 01:44, Andy Shevchenko wrote:
> 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.

I'd say Yes. (and #undef DEF_PAGETYPE_NAME methinks; or change both to _MASK)

--
~Randy