Re: [PATCH v2 2/4] zram: avoid disksize setting when device is being claimed

From: Minchan Kim
Date: Wed May 19 2021 - 15:56:22 EST


On Fri, Apr 23, 2021 at 01:11:06AM +0000, Luis Chamberlain wrote:
> As with other areas of the zram diver, check if the zram
> block device is being claimed but do it early to avoid
> trying to set something up for a zram device which may
> be on its way out.

I guess you're talking about zram_remove race with disksize_store.
Please add some code sequence diagram like previous patch, which
makes thing more clear.

Otherwise, looks good to me.

>
> This doesn't fix a known crash, however the potential for
> an issue issue is found through code inspection.
>
> Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> ---
> drivers/block/zram/zram_drv.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 431b60cd85c1..6051d20b88c3 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1729,7 +1729,7 @@ static ssize_t disksize_store(struct device *dev,
>
> mutex_lock(&zram_index_mutex);
>
> - if (!zram_up) {
> + if (!zram_up || zram->claim) {
> err = -ENODEV;
> goto out;
> }
> --
> 2.27.0
>