linux-kernel - Re: [PATCH V2 3/4] zram: avoid race between zram_remove and disksize

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Message-ID: <YXMK0l5lDeIH8qMQ@bombadil.infradead.org>
Date:   Fri, 22 Oct 2021 12:02:42 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Ming Lei <ming.lei@...hat.com>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
        Minchan Kim <minchan@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 3/4] zram: avoid race between zram_remove and
 disksize_store

On Wed, Oct 20, 2021 at 09:55:47AM +0800, Ming Lei wrote:
> After resetting device in zram_remove(), disksize_store still may come and
> allocate resources again before deleting gendisk, fix the race by resetting
> zram after del_gendisk() returns. At that time, disksize_store can't come
> any more.
> 
> Reported-by: Luis Chamberlain <mcgrof@...nel.org>
> Signed-off-by: Ming Lei <ming.lei@...hat.com>
> ---
>  drivers/block/zram/zram_drv.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 8883de7aa3d7..6078d1dae44a 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -2002,6 +2002,13 @@ static int zram_remove(struct zram *zram)
>  	/* del_gendisk drains pending reset_store */
>  	WARN_ON_ONCE(claimed && zram->claim);
>  
> +	/*
> +	 * disksize store may come between zram_reset_device and del_gendisk, so
> +	 * run the last reset for avoiding leak anything allocated in
> +	 * disksize_store().

The above is not clear English, how about:

disksize_store() may be called in between zram_reset_device() and
del_gendisk(), so run the last reset to avoid leaking anything allocated
with disksize_store()

Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>

  Luis