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

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Date:   Tue, 2 Aug 2022 11:54:10 +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 Mon, Aug 01, 2022 at 03:36:48PM +0200, Vlastimil Babka wrote:
> On 8/1/22 15:26, Hyeonggon Yoo wrote:
> > 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.
> 
> You mean "will NOT affect...", right?

Ah, yes. mistake.

> 
> > - 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.
> 
> Ah, right. __kmalloc_large_node_notrace() does the same  flags |=
> __GFP_COMP; but the tracepoint is outside and unaffected.

I'll reflect your suggestion anyway.

-- 
Thanks,
Hyeonggon