linux-kernel - Re: [PATCH v3 06/15] mm/slab_common: fold kmalloc_order_trace() into kmalloc

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Message-ID: <2e252179-0ffe-0d9c-9340-77e46f6ffdfd@suse.cz>
Date:   Thu, 28 Jul 2022 17:23:29 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Joe Perches <joe@...ches.com>,
        Vasily Averin <vasily.averin@...ux.dev>,
        Matthew WilCox <willy@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 06/15] mm/slab_common: fold kmalloc_order_trace() into
 kmalloc_large()

On 7/12/22 15:39, Hyeonggon Yoo wrote:
> There is no caller of kmalloc_order_trace() except kmalloc_large().
> Fold it into kmalloc_large() and remove kmalloc_order{,_trace}().
> 
> Also add tracepoint in kmalloc_large() that was previously
> in kmalloc_order_trace().
> 
> Signed-off-by: Hyeonggon Yoo <42.hyeyoo@...il.com>
> Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

Hmm noticed a small change in how we call trace_kmalloc() which will now
include the __GFP_COMP. I think we could just call alloc_pages() from
kmalloc_large() with flags | __GFP_COMP instead of doing flags |=
__GFP_COMP; first. AFAICS both kasan_kmalloc_large() and kmemleak_alloc()
will filter it out anyway.

> ---
>  include/linux/slab.h | 22 ++--------------------
>  mm/slab_common.c     | 14 +++-----------
>  2 files changed, 5 insertions(+), 31 deletions(-)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index a0e57df3d5a4..15a4c59da59e 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -489,26 +489,8 @@ static __always_inline void *kmem_cache_alloc_node_trace(struct kmem_cache *s, g
>  }
>  #endif /* CONFIG_TRACING */
>  
> -extern void *kmalloc_order(size_t size, gfp_t flags, unsigned int order) __assume_page_alignment
> -									 __alloc_size(1);
> -
> -#ifdef CONFIG_TRACING
> -extern void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
> -				__assume_page_alignment __alloc_size(1);
> -#else
> -static __always_inline __alloc_size(1) void *kmalloc_order_trace(size_t size, gfp_t flags,
> -								 unsigned int order)
> -{
> -	return kmalloc_order(size, flags, order);
> -}
> -#endif
> -
> -static __always_inline __alloc_size(1) void *kmalloc_large(size_t size, gfp_t flags)
> -{
> -	unsigned int order = get_order(size);
> -	return kmalloc_order_trace(size, flags, order);
> -}
> -
> +void *kmalloc_large(size_t size, gfp_t flags) __assume_page_alignment
> +					      __alloc_size(1);
>  /**
>   * kmalloc - allocate memory
>   * @size: how many bytes of memory are required.
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 6c9aac5d8f4a..1f8af2106df0 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -932,10 +932,11 @@ gfp_t kmalloc_fix_flags(gfp_t flags)
>   * directly to the page allocator. We use __GFP_COMP, because we will need to
>   * know the allocation order to free the pages properly in kfree.
>   */
> -void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
> +void *kmalloc_large(size_t size, gfp_t flags)
>  {
>  	void *ret = NULL;
>  	struct page *page;
> +	unsigned int order = get_order(size);
>  
>  	if (unlikely(flags & GFP_SLAB_BUG_MASK))
>  		flags = kmalloc_fix_flags(flags);
> @@ -950,19 +951,10 @@ void *kmalloc_order(size_t size, gfp_t flags, unsigned int order)
>  	ret = kasan_kmalloc_large(ret, size, flags);
>  	/* As ret might get tagged, call kmemleak hook after KASAN. */
>  	kmemleak_alloc(ret, size, 1, flags);
> -	return ret;
> -}
> -EXPORT_SYMBOL(kmalloc_order);
> -
> -#ifdef CONFIG_TRACING
> -void *kmalloc_order_trace(size_t size, gfp_t flags, unsigned int order)
> -{
> -	void *ret = kmalloc_order(size, flags, order);
>  	trace_kmalloc(_RET_IP_, ret, NULL, size, PAGE_SIZE << order, flags);
>  	return ret;
>  }
> -EXPORT_SYMBOL(kmalloc_order_trace);
> -#endif
> +EXPORT_SYMBOL(kmalloc_large);
>  
>  #ifdef CONFIG_SLAB_FREELIST_RANDOM
>  /* Randomize a generic freelist */