linux-kernel - Re: [PATCH mm-unstable v4 2/3] mm, printk: introduce new format %pGt for page

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Date:   Fri, 3 Mar 2023 20:50:52 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew WilCox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm-unstable v4 2/3] mm, printk: introduce new format %pGt
 for page_type

On Mon 2023-01-30 13:25:13, Hyeonggon Yoo wrote:
> %pGp format is used to display 'flags' field of a struct page.
> However, some page flags (i.e. PG_buddy, see page-flags.h for more details)
> are stored in page_type field. To display human-readable output of
> page_type, introduce %pGt format.
> 
> It is important to note the meaning of bits are different in page_type.
> if page_type is 0xffffffff, no flags are set. Setting PG_buddy (0x00000080)
> flag results in a page_type of 0xffffff7f. Clearing a bit actually means
> setting a flag. Bits in page_type are inverted when displaying type names.
> 
> Only values for which page_type_has_type() returns true are considered
> as page_type, to avoid confusion with mapcount values. if it returns false,
> only raw values are displayed and not page type names.
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

Reviewed-by: Petr Mladek <pmladek@...e.com>   # for vsprintf part

I am sorry for the late review. It has somehow fallen through cracks.

Best Regards,
Petr