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

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Message-ID: <YufUgFX2shlG5FoR@hyeyoo>
Date:   Mon, 1 Aug 2022 22:26:24 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     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>,
        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 Thu, Jul 28, 2022 at 05:23:29PM +0200, Vlastimil Babka wrote:
> 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>
> 

Thank you for review.

> Hmm noticed a small change in how we call trace_kmalloc() which will now
> include the __GFP_COMP.

Good catch.

> I think we could just call alloc_pages() from
> kmalloc_large() with flags | __GFP_COMP instead of doing flags |=
> __GFP_COMP; first.

I'll consider that in next version.

> AFAICS both kasan_kmalloc_large() and kmemleak_alloc()
> will filter it out anyway.

AFAIK not passing __GFP_COMP to both kasan_kmalloc_large()
and kmemleak_alloc() will affect their behavior.

- kasan_kmalloc_large() only checks if flag has __GFP_DIRECT_RECLAIM,
- kmemleak_alloc() only use it to allocate kmemleak_object from
  slab/pool, which does not require __GFP_COMP.

simply calling
	alloc_pages() with flags | GFP_COMP
	kasan_kmalloc_large() with flags
	kmemleak_alloc() with flags
	trace_kmalloc() with flags
will be okay.

BTW this is fixed after patch 9.

> > ---
> >  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 */
> 

-- 
Thanks,
Hyeonggon