Subject: Re: [PATCH 4/7] mm, pagemap: remove SLOB and SLQB from comments and documentation

From: Hyeonggon Yoo <[email-masked]>
Date: Tue, 14 Mar 2023 08:19:18 +0000

On Fri, Mar 10, 2023 at 11:32:06AM +0100, Vlastimil Babka wrote:
> SLOB has been removed and SLQB never merged, so remove their mentions
> from comments and documentation of pagemap.
> 
> Signed-off-by: Vlastimil Babka <[email-masked]>
> ---
>  Documentation/admin-guide/mm/pagemap.rst | 6 +++---
>  fs/proc/page.c                           | 5 ++---
>  2 files changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
> index b5f970dc91e7..bb4aa897a773 100644
> --- a/Documentation/admin-guide/mm/pagemap.rst
> +++ b/Documentation/admin-guide/mm/pagemap.rst
> @@ -91,9 +91,9 @@ Short descriptions to the page flags
>     The page is being locked for exclusive access, e.g. by undergoing read/write
>     IO.
>  7 - SLAB
> -   The page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator.
> -   When compound page is used, SLUB/SLQB will only set this flag on the head
> -   page; SLOB will not flag it at all.
> +   The page is managed by the SLAB/SLUB kernel memory allocator.
> +   When compound page is used, either will only set this flag on the head
> +   page..
>  10 - BUDDY
>      A free memory block managed by the buddy system allocator.
>      The buddy system organizes free memory in blocks of various orders.
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 6249c347809a..1356aeffd8dc 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -125,7 +125,7 @@ u64 stable_page_flags(struct page *page)
>  	/*
>  	 * pseudo flags for the well known (anonymous) memory mapped pages
>  	 *
> -	 * Note that page->_mapcount is overloaded in SLOB/SLUB/SLQB, so the
> +	 * Note that page->_mapcount is overloaded in SLAB/SLUB, so the

SLUB does not overload _mapcount.

>  	 * simple test in page_mapped() is not enough.
>  	 */
>  	if (!PageSlab(page) && page_mapped(page))
> @@ -166,8 +166,7 @@ u64 stable_page_flags(struct page *page)
>  
>  	/*
>  	 * Caveats on high order pages: page->_refcount will only be set
> -	 * -1 on the head page; SLUB/SLQB do the same for PG_slab;
> -	 * SLOB won't set PG_slab at all on compound pages.
> +	 * -1 on the head page; SLAB/SLUB do the same for PG_slab;

I think this comment could be just saying that PG_buddy is only set on
head page, not saying

_refcount is set to -1 on head page (is it even correct?)

>  	 */
>  	if (PageBuddy(page))
>  		u |= 1 << KPF_BUDDY;
> -- 
> 2.39.2