linux-kernel - Re: Cannot parse struct or union error on mm-everything

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Message-ID: <87c11d37-50ab-2c81-c454-d085c1fdff52@infradead.org>
Date:   Fri, 18 Nov 2022 21:26:47 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Bagas Sanjaya <bagasdotme@...il.com>,
        Linux Documentation <linux-doc@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Peter Xu <peterx@...hat.com>, Yu Zhao <yuzhao@...gle.com>,
        Colin Cross <ccross@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Subject: Re: Cannot parse struct or union error on mm-everything



On 11/18/22 20:10, Bagas Sanjaya wrote:
> Greetings,
> 
> I found a new htmldocs warning on mm-everything:
> 
> WARNING: kernel-doc './scripts/kernel-doc -rst -enable-lineno -sphinx-version 2.4.4 -internal ./include/linux/mm_types.h' failed with return code 1
> 
> Checking the header with './scripts/kernel-doc -v -none 
> ./include/linux/mm_types.h', I got the full error:
> 
> include/linux/mm_types.h:255: info: Scanning doc for struct encoded_page
> include/linux/mm_types.h:268: error: Cannot parse struct or union!
> include/linux/mm_types.h:287: info: Scanning doc for struct folio
> include/linux/mm_types.h:917: info: Scanning doc for typedef vm_fault_t
> include/linux/mm_types.h:924: info: Scanning doc for enum vm_fault_reason
> include/linux/mm_types.h:1028: info: Scanning doc for enum fault_flag
> 1 errors
> 
> The culprit is encoded_page struct, which is null struct (nonexistent type)
> with kernel-doc comments:
> 
> /**
>  * struct encoded_page - a nonexistent type marking this pointer
>  *
>  * An 'encoded_page' pointer is a pointer to a regular 'struct page', but
>  * with the low bits of the pointer indicating extra context-dependent
>  * information. Not super-common, but happens in mmu_gather and mlock
>  * handling, and this acts as a type system check on that use.
>  *
>  * We only really have two guaranteed bits in general, although you could
>  * play with 'struct page' alignment (see CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
>  * for more.
>  *
>  * Use the supplied helper functions to endcode/decode the pointer and bits.
>  */
> struct encoded_page;
> 
> The struct is introduced by d57ab372568585 ("mm: introduce 'encoded' page
> pointers with embedded extra bits").

https://lore.kernel.org/all/CAHk-=wiyYSrBiOKJEV3phOBDT7EMgdXCnDUrp57E8HGNT4SFdA@mail.gmail.com/

I guess that nobody has "fixed" it yet.

-- 
~Randy