[CRIU] [PATCH 3/9] mount: link dependent mounts

[Pavel Emelyanov]

On 07/09/2013 03:05 PM, Andrey Vagin wrote:
> All shared mounts from one group are connected to circular list.
> All slave are added into the proper master list.
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/proc_parse.h |  5 ++++
>  mount.c              | 81 ++++++++++++++++++++++++++++++++--------------------
>  2 files changed, 55 insertions(+), 31 deletions(-)
> 
> diff --git a/include/proc_parse.h b/include/proc_parse.h
> index 8c2c36e..99255c4 100644
> --- a/include/proc_parse.h
> +++ b/include/proc_parse.h
> @@ -116,6 +116,11 @@ struct mount_info {
>  	struct mount_info *parent;
>  	struct list_head children;
>  	struct list_head siblings;
> +
> +	struct list_head mnt_share;	/* circular list of shared mounts */
> +	struct list_head mnt_slave_list;/* list of slave mounts */
> +	struct list_head mnt_slave;	/* slave list entry */
> +	struct mount_info *mnt_master;	/* slave is on master->mnt_slave_list */
>  };
>  
>  struct proc_posix_timer {
> diff --git a/mount.c b/mount.c
> index fbc9f7d..1971c26 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -178,6 +178,51 @@ static void mnt_tree_show(struct mount_info *tree, int off)
>  	pr_info("%*s<--\n", off, "");
>  }
>  
> +static int collect_shared(struct mount_info *info)
> +{
> +	struct mount_info *m, *t;
> +
> +	/*
> +	 * If we have a shared mounts, both master
> +	 * slave targets are to be present in mount
> +	 * list, otherwise we can't be sure if we can
> +	 * recreate the scheme later on restore.
> +	 */
> +	for (m = info; m; m = m->next) {
> +		bool share, master;
> +
> +		share = m->shared_id && list_empty(&m->mnt_share);
> +		master = m->master_id;

master is bool, master_id is int. What's going on here?

> +
> +		for (t = info; t && (share || master); t = t->next) {
> +			if (t == m)
> +				continue;
> +			if (master && t->shared_id == m->master_id) {
> +				pr_debug("The mount %d is slave for %d\n", m->mnt_id, t->mnt_id);
> +				list_add(&m->mnt_slave, &t->mnt_slave_list);
> +				m->mnt_master = t;
> +				master = false;
> +			}
> +
> +			/* Collect all mounts for this group */
> +			if (share && t->shared_id == m->shared_id) {
> +				pr_debug("Mount %d is shared with %d group %d\n",
> +						m->mnt_id, t->mnt_id, m->shared_id);
> +				list_add(&m->mnt_share, &t->mnt_share);

Shouldn't "share = false" be here? Otherwise we may add m to several mnt_share lists.

> +			}
> +		}
> +		if (!master)
> +			continue;
> +
> +		pr_err("Mount %d (master_id: %d shared_id: %d) "
> +		       "has unreachable sharing\n", m->mnt_id,
> +			m->master_id, m->shared_id);
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
>  static struct mount_info *mnt_build_tree(struct mount_info *list)
>  {
>  	struct mount_info *tree;
> @@ -192,6 +237,7 @@ static struct mount_info *mnt_build_tree(struct mount_info *list)
>  		return NULL;
>  
>  	mnt_resort_siblings(tree);
> +	collect_shared(tree);
>  	pr_info("Done:\n");
>  	mnt_tree_show(tree, 0);
>  	return tree;
> @@ -396,36 +442,6 @@ static inline int is_root_mount(struct mount_info *mi)
>  	return is_root(mi->mountpoint);
>  }
>  
> -static int validate_shared(struct mount_info *info)
> -{
> -	struct mount_info *m, *t;
> -
> -	/*
> -	 * If we have a shared mounts, both master
> -	 * slave targets are to be present in mount
> -	 * list, otherwise we can't be sure if we can
> -	 * recreate the scheme later on restore.
> -	 */
> -	for (m = info; m; m = m->next) {
> -		if (!m->master_id)
> -			continue;
> -
> -		for (t = info; t; t = t->next) {
> -			if (t->shared_id == m->master_id)
> -				break;
> -		}
> -		if (t)
> -			continue;
> -
> -		pr_err("Mount %d (master_id: %d shared_id: %d) "
> -		       "has unreachable sharing\n", m->mnt_id,
> -			m->master_id, m->shared_id);
> -		return -1;
> -	}
> -
> -	return 0;
> -}
> -
>  static int dump_one_mountpoint(struct mount_info *pm, int fd)
>  {
>  	MntEntry me = MNT_ENTRY__INIT;
> @@ -469,7 +485,7 @@ int dump_mnt_ns(int ns_pid, struct cr_fdset *fdset)
>  		return -1;
>  	}
>  
> -	if (validate_shared(mntinfo)) {
> +	if (collect_shared(mntinfo)) {
>  		pr_err("Can't proceed %d's mountinfo\n", ns_pid);
>  		return -1;
>  	}
> @@ -682,6 +698,9 @@ struct mount_info *mnt_entry_alloc()
>  	if (new) {
>  		INIT_LIST_HEAD(&new->children);
>  		INIT_LIST_HEAD(&new->siblings);
> +		INIT_LIST_HEAD(&new->mnt_slave_list);
> +		INIT_LIST_HEAD(&new->mnt_share);
> +		new->mnt_master = NULL;
>  	}
>  	return new;
>  }
>