linux-kernel - Re: [PATCH] mmc: block: Fix memory leak in blk-mq when cleaning up

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Date:   Fri, 3 May 2019 17:20:41 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Guenter Roeck <groeck@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Ming Lei <ming.lei@...hat.com>, linux-mmc@...r.kernel.org,
        Hannes Reinecke <hare@...e.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>, Omar Sandoval <osandov@...com>
Subject: Re: [PATCH] mmc: block: Fix memory leak in blk-mq when cleaning up

On Fri, May 3, 2019 at 4:35 PM Douglas Anderson <dianders@...omium.org> wrote:
>
> If I run the following on rk3288-veyron-minnie (a 2GB machine)
>
>   cd /sys/bus/platform/drivers/dwmmc_rockchip
>   for i in $(seq 1 3000); do
>     echo "========================" $i
>     echo ff0f0000.dwmmc > unbind
>     sleep .5
>     echo ff0f0000.dwmmc > bind
>     while true; do
>       if [ -e /dev/mmcblk2 ]; then
>         break;
>       fi
>       sleep .1
>     done
>   done
>
> Then I start OOMing somewhere between iteration 200 and 250.  Using
> kmemleak, I see reports like:
>
> unreferenced object 0xe39c5580 (size 64):
>   comm "kworker/1:0", pid 17, jiffies 4294821091 (age 96.952s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ad19d10a>] __kmalloc+0x1ec/0x2dc
>     [<a28614c3>] blk_mq_alloc_tag_set+0x27c/0x2bc
>     [<0955ae01>] mmc_init_queue+0xa8/0x2a8
>     [<5102b986>] mmc_blk_alloc_req+0xf8/0x2d4
>     [<f1c2214f>] mmc_blk_probe+0x4a8/0x6c0
>     [<0dfdd9d5>] mmc_bus_probe+0x24/0x28
>
> It's pretty clear that we're missing a call to blk_mq_free_tag_set().
> Let's add it.
>
> Fixes: 81196976ed94 ("mmc: block: Add blk-mq support")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Nice one.

Reviewed-by: Guenter Roeck <groeck@...omium.org>

> ---
>
>  drivers/mmc/core/queue.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index 7c364a9c4eeb..09071e13282e 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -480,6 +480,8 @@ void mmc_cleanup_queue(struct mmc_queue *mq)
>          */
>         flush_work(&mq->complete_work);
>
> +       blk_mq_free_tag_set(&mq->tag_set);
> +
>         mq->card = NULL;
>  }
>
> --
> 2.21.0.1020.gf2820cf01a-goog
>