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

[SeongJae Park]

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?

> 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
> 
>