linux-kernel - Re: [PATCH v2 3/6] mm, pagemap: remove SLOB and SLQB from comments and documentation

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Message-ID: <ZBRUKdaAfBMcSWzD@kernel.org>
Date:   Fri, 17 Mar 2023 13:51:05 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        rcu@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        linux-doc@...r.kernel.org, Lorenzo Stoakes <lstoakes@...il.com>
Subject: Re: [PATCH v2 3/6] mm, pagemap: remove SLOB and SLQB from comments
 and documentation

On Fri, Mar 17, 2023 at 11:43:04AM +0100, Vlastimil Babka wrote:
> SLOB has been removed and SLQB never merged, so remove their mentions
> from comments and documentation of pagemap.
> 
> In stable_page_flags() also correct an outdated comment mentioning that
> PageBuddy() means a page->_refcount of -1, and remove compound_head()
> from the PageSlab() call, as that's already implicitly there thanks to
> PF_NO_TAIL.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
> Acked-by: Lorenzo Stoakes <lstoakes@...il.com>

Acked-by: Mike Rapoport (IBM) <rppt@...nel.org>

> ---
>  Documentation/admin-guide/mm/pagemap.rst | 6 +++---
>  fs/proc/page.c                           | 9 ++++-----
>  2 files changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst
> index b5f970dc91e7..c8f380271cad 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..195b077c0fac 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, so the
>  	 * simple test in page_mapped() is not enough.
>  	 */
>  	if (!PageSlab(page) && page_mapped(page))
> @@ -165,9 +165,8 @@ 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.
> +	 * Caveats on high order pages: PG_buddy and PG_slab will only be set
> +	 * on the head page.
>  	 */
>  	if (PageBuddy(page))
>  		u |= 1 << KPF_BUDDY;
> @@ -185,7 +184,7 @@ u64 stable_page_flags(struct page *page)
>  	u |= kpf_copy_bit(k, KPF_LOCKED,	PG_locked);
>  
>  	u |= kpf_copy_bit(k, KPF_SLAB,		PG_slab);
> -	if (PageTail(page) && PageSlab(compound_head(page)))
> +	if (PageTail(page) && PageSlab(page))
>  		u |= 1 << KPF_SLAB;
>  
>  	u |= kpf_copy_bit(k, KPF_ERROR,		PG_error);
> -- 
> 2.39.2
> 

-- 
Sincerely yours,
Mike.