Re: [PATCH v2 1/2] mm/damon/core-test: Fix memory leak in damon_new_region()

[Ruan Jinjie]

On 2023/9/18 19:00, SeongJae Park wrote:
> Hi Jinjie,
> 
> On Mon, 18 Sep 2023 15:47:58 +0800 Jinjie Ruan <ruanjinjie@xxxxxxxxxx> wrote:
> 
>> When CONFIG_DAMON_KUNIT_TEST=y and making CONFIG_DEBUG_KMEMLEAK=y
>> and CONFIG_DEBUG_KMEMLEAK_AUTO_SCAN=y, the below memory leak is detected.
>>
>> The damon_region which is allocated by kmem_cache_alloc() in
>> damon_new_region() in damon_test_regions() and
>> damon_test_update_monitoring_result() are not freed. So use
>> damon_free_region() to free it.
> 
> Nit.  This patch is not directly adding use of damon_free_region() but replaces
> damon_del_region() call with damon_destroy_region(), so that it calls both
> damon_del_region() and damon_free_region().
> 
> I think this part might better to be re-written?

OK. Thank you!

> 
>> After applying this patch, the following
>> memory leak is never detected.
>>
>>     unreferenced object 0xffff2b49c3edc000 (size 56):
>>       comm "kunit_try_catch", pid 338, jiffies 4294895280 (age 557.084s)
>>       hex dump (first 32 bytes):
>>         01 00 00 00 00 00 00 00 02 00 00 00 00 00 00 00  ................
>>         00 00 00 00 00 00 00 00 00 00 00 00 49 2b ff ff  ............I+..
>>       backtrace:
>>         [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
>>         [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
>>         [<000000008603f022>] damon_new_region+0x28/0x54
>>         [<00000000a3b8c64e>] damon_test_regions+0x38/0x270
>>         [<00000000559c4801>] kunit_try_run_case+0x50/0xac
>>         [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
>>         [<000000003c3e9211>] kthread+0x124/0x130
>>         [<0000000028f85bdd>] ret_from_fork+0x10/0x20
>>     unreferenced object 0xffff2b49c5b20000 (size 56):
>>       comm "kunit_try_catch", pid 354, jiffies 4294895304 (age 556.988s)
>>       hex dump (first 32 bytes):
>>         03 00 00 00 00 00 00 00 07 00 00 00 00 00 00 00  ................
>>         00 00 00 00 00 00 00 00 96 00 00 00 49 2b ff ff  ............I+..
>>       backtrace:
>>         [<0000000088e71769>] slab_post_alloc_hook+0xb8/0x368
>>         [<00000000b528f67c>] kmem_cache_alloc+0x168/0x284
>>         [<000000008603f022>] damon_new_region+0x28/0x54
>>         [<00000000ca019f80>] damon_test_update_monitoring_result+0x18/0x34
>>         [<00000000559c4801>] kunit_try_run_case+0x50/0xac
>>         [<000000003932ed49>] kunit_generic_run_threadfn_adapter+0x20/0x2c
>>         [<000000003c3e9211>] kthread+0x124/0x130
>>         [<0000000028f85bdd>] ret_from_fork+0x10/0x20
>>
>> Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests")
>> Fixes: f4c978b6594b ("mm/damon/core-test: add a test for damon_update_monitoring_results()")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
> 
> Other than the above trivial nit,
> 
> Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
> 
>> ---
>> v2:
>> - Replace the damon_del_region() with damon_destroy_region() rather than
>>   calling damon_free_region().
>> - Update the commit message.
> 
> And thank you for making the changes.
> 
> 
> Thanks,
> SJ
> 
>> ---
>>  mm/damon/core-test.h | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h
>> index 79f1f12e0dd5..3959be35b901 100644
>> --- a/mm/damon/core-test.h
>> +++ b/mm/damon/core-test.h
>> @@ -30,7 +30,7 @@ static void damon_test_regions(struct kunit *test)
>>  	damon_add_region(r, t);
>>  	KUNIT_EXPECT_EQ(test, 1u, damon_nr_regions(t));
>>  
>> -	damon_del_region(r, t);
>> +	damon_destroy_region(r, t);
>>  	KUNIT_EXPECT_EQ(test, 0u, damon_nr_regions(t));
>>  
>>  	damon_free_target(t);
>> @@ -321,6 +321,8 @@ static void damon_test_update_monitoring_result(struct kunit *test)
>>  	damon_update_monitoring_result(r, &old_attrs, &new_attrs);
>>  	KUNIT_EXPECT_EQ(test, r->nr_accesses, 150);
>>  	KUNIT_EXPECT_EQ(test, r->age, 20);
>> +
>> +	damon_free_region(r);
>>  }
>>  
>>  static void damon_test_set_attrs(struct kunit *test)
>> -- 
>> 2.34.1
>>
>>