[CRIU] [PATCH 1/6] mnt: add a function to check whether a mount overmounts something

[Pavel Emelyanov]

On 09/13/2016 07:19 AM, Andrei Vagin wrote:
> From: Andrei Vagin <avagin at virtuozzo.com>
> 
> This function is going to be used more than once.
> 
> Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
> ---
>  criu/mount.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/criu/mount.c b/criu/mount.c
> index fe120a1..797edd7 100644
> --- a/criu/mount.c
> +++ b/criu/mount.c
> @@ -637,6 +637,23 @@ static struct mount_info *find_fsroot_mount_for(struct mount_info *bm)
>  	return NULL;
>  }
>  
> +static bool does_mnt_overmount(struct mount_info *m)
> +{
> +	struct mount_info *t;
> +
> +	if (!m->parent)
> +		return false;
> +
> +	list_for_each_entry(t, &m->parent->children, siblings) {
> +		if (m == t)
> +			continue;
> +		if (issubpath(t->mountpoint, m->mountpoint))
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  static int validate_mounts(struct mount_info *info, bool for_dump)
>  {
>  	struct mount_info *m, *t;
> @@ -701,13 +718,10 @@ static int validate_mounts(struct mount_info *info, bool for_dump)
>  			}
>  		}
>  skip_fstype:
> -		list_for_each_entry(t, &m->parent->children, siblings) {
> -			if (m == t)
> -				continue;
> -			if (!issubpath(m->mountpoint, t->mountpoint))
> -				continue;
> -
> -			pr_err("%d:%s is overmounted\n", m->mnt_id, m->mountpoint);
> +		if (does_mnt_overmount(m) &&
> +		    !list_empty(&m->parent->mnt_share)) {

This check is new (for mnt_share list). Why is it here?

> +			pr_err("Unable to handle mounts under %d:%s\n",
> +					m->mnt_id, m->mountpoint);
>  			return -1;
>  		}
>  	}
>