[dm-devel] dm raid: avoid mddev->suspended access

[Mike Snitzer]

On Thu, Jul 13 2017 at 11:34am -0400,
heinzm at redhat.com <heinzm at redhat.com> wrote:

> From: Heinz Mauelshagen <heinzm at redhat.com>
> 
> Use runtime flag to ensure that an mddev gets suspended/resumed just once.
> 
> Signed-off-by: Heinz Mauelshagen <heinzm at redhat.com>
> ---
>  drivers/md/dm-raid.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index b409015..60c524b 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -208,6 +208,7 @@ struct raid_dev {
>  #define RT_FLAG_RS_BITMAP_LOADED	2
>  #define RT_FLAG_UPDATE_SBS		3
>  #define RT_FLAG_RESHAPE_RS		4
> +#define RT_FLAG_RS_SUSPENDED		5
>  
>  /* Array elements of 64 bit needed for rebuild/failed disk bits */
>  #define DISKS_ARRAY_ELEMS ((MAX_RAID_DEVICES + (sizeof(uint64_t) * 8 - 1)) / sizeof(uint64_t) / 8)
> @@ -3169,6 +3170,7 @@ static int raid_ctr(struct dm_target *ti, unsigned int argc, char **argv)
>  	}
>  
>  	mddev_suspend(&rs->md);
> +	set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags);
>  
>  	/* Try to adjust the raid4/5/6 stripe cache size to the stripe size */
>  	if (rs_is_raid456(rs)) {
> @@ -3626,7 +3628,7 @@ static void raid_postsuspend(struct dm_target *ti)
>  {
>  	struct raid_set *rs = ti->private;
>  
> -	if (!rs->md.suspended)
> +	if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
>  		mddev_suspend(&rs->md);
>  
>  	rs->md.ro = 1;
> @@ -3760,7 +3762,7 @@ static int rs_start_reshape(struct raid_set *rs)
>  		return r;
>  
>  	/* Need to be resumed to be able to start reshape, recovery is frozen until raid_resume() though */
> -	if (mddev->suspended)
> +	if (test_and_clear_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
>  		mddev_resume(mddev);
>  
>  	/*
> @@ -3787,8 +3789,8 @@ static int rs_start_reshape(struct raid_set *rs)
>  	}
>  
>  	/* Suspend because a resume will happen in raid_resume() */
> -	if (!mddev->suspended)
> -		mddev_suspend(mddev);
> +	set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags);
> +	mddev_suspend(mddev);
>  
>  	/*
>  	 * Now reshape got set up, update superblocks to

Shouldn't this be the following?

if (!test_and_set_bit(RT_FLAG_RS_SUSPENDED, &rs->runtime_flags))
   mddev_suspend(mddev);