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Message-ID: <b3d4255d-2a63-b2cb-bd1b-dc7812d95fe9@suse.cz>
Date:   Wed, 6 Apr 2022 11:03:24 +0200
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Subject: Re: [PATCH v3 3/6] mm/slub: use stackdepot to save stack trace in
 objects
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To:     David Rientjes <rientjes@google.com>
Cc:     Christoph Lameter <cl@linux.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Pekka Enberg <penberg@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        patches@lists.linux.dev, linux-kernel@vger.kernel.org,
        Oliver Glitta <glittao@gmail.com>,
        Marco Elver <elver@google.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Hyeonggon Yoo <42.hyeyoo@gmail.com>,
        Imran Khan <imran.f.khan@oracle.com>
References: <20220404164112.18372-1-vbabka@suse.cz>
 <20220404164112.18372-4-vbabka@suse.cz>
 <5f7d33ec-1e73-cdfc-54e5-e93d346ac78@google.com>
From:   Vlastimil Babka <vbabka@suse.cz>
In-Reply-To: <5f7d33ec-1e73-cdfc-54e5-e93d346ac78@google.com>
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On 4/5/22 23:40, David Rientjes wrote:
>> -static void set_track(struct kmem_cache *s, void *object,
>> +static void noinline set_track(struct kmem_cache *s, void *object,
>>  			enum track_item alloc, unsigned long addr)
>>  {
>>  	struct track *p = get_track(s, object, alloc);
>>  
>> -#ifdef CONFIG_STACKTRACE
>> +#ifdef CONFIG_STACKDEPOT
>> +	unsigned long entries[TRACK_ADDRS_COUNT];
>>  	unsigned int nr_entries;
>>  
>> -	metadata_access_enable();
>> -	nr_entries = stack_trace_save(kasan_reset_tag(p->addrs),
>> -				      TRACK_ADDRS_COUNT, 3);
>> -	metadata_access_disable();
>> -
>> -	if (nr_entries < TRACK_ADDRS_COUNT)
>> -		p->addrs[nr_entries] = 0;
>> +	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 3);
>> +	p->handle = stack_depot_save(entries, nr_entries, GFP_NOWAIT);
> 
> I think this should also have __GFP_NOWARN set since this allocation could 
> easily fail and it would unnecessarily spam the kernel log unless we 
> actually care about the stack trace being printed later (and the patch 
> already indicates the allocation failed in print_track() when it matters).

Good point. But turns out __stack_depot_save() adds it for us already.

> Otherwise:
> 
> Acked-by: David Rientjes <rientjes@google.com>

Thanks!