[CRIU] [PATCH 7/9] mounts: if a mount can't be mounted, it is queued in postpone list

[Pavel Emelyanov]

On 07/09/2013 03:05 PM, Andrey Vagin wrote:
> Try to restore mounts while a postpone list isn't empty and check
> that each iteration has some progress, otherwice it will fails for
> preventing infinite loops
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  include/proc_parse.h |  2 ++
>  mount.c              | 40 ++++++++++++++++++++++++++++++++++++----
>  2 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/include/proc_parse.h b/include/proc_parse.h
> index 1325424..85bde36 100644
> --- a/include/proc_parse.h
> +++ b/include/proc_parse.h
> @@ -123,6 +123,8 @@ struct mount_info {
>  	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 list_head postpone;
>  };
>  
>  struct proc_posix_timer {
> diff --git a/mount.c b/mount.c
> index 0609ded..fae9513 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -533,12 +533,25 @@ int dump_mnt_ns(int ns_pid, struct cr_fdset *fdset)
>  	return 0;
>  }
>  
> -#define MNT_TREE_WALK(_r, _el, _fn_f, _fn_r) do {				\
> +static int mount_progress;
> +
> +#define MNT_TREE_WALK(_r, _el, _fn_f, _fn_r, _plist) do {			\
>  		struct mount_info *_mi = _r;					\
>  										\
>  		while (1) {							\
> -			if (_fn_f(_mi))						\
> +			int ret;						\
> +										\
> +			ret = _fn_f(_mi);					\
> +			if (ret < 0)						\
>  				return -1;					\
> +			else if (ret > 0) {					\
> +				list_add_tail(&_mi->postpone, _plist);		\

_plist can be NULL here, can't it?

> +				goto up;					\
> +			}							\
> +										\
> +			list_del(&_mi->postpone);				\
> +			mount_progress++;					\
> +										\
>  			if (!list_empty(&_mi->children)) {			\
>  				_mi = list_entry(_mi->children._el,		\
>  						struct mount_info, siblings);	\
> @@ -564,13 +577,32 @@ int dump_mnt_ns(int ns_pid, struct cr_fdset *fdset)
>  static int mnt_tree_for_each(struct mount_info *m,
>  		int (*fn)(struct mount_info *))
>  {
> -	MNT_TREE_WALK(m, next, fn, MNT_WALK_NONE);
> +	static LIST_HEAD(postpone);
> +
> +	list_add(&m->postpone, &postpone);
> +
> +	while (!list_empty(&postpone)) {
> +		int old = mount_progress;
> +		list_for_each_entry(m, &postpone, postpone)
> +			MNT_TREE_WALK(m, next, fn, MNT_WALK_NONE, &postpone);

Can you please rewrite this using either do { } while (!list_empty) or
use backwards goto for easier reading.

> +		if (old == mount_progress) {
> +			pr_err("A few mount points can't be mounted");
> +			list_for_each_entry(m, &postpone, postpone) {
> +				pr_err("%d:%d %s %s %s\n", m->mnt_id,
> +					m->parent_mnt_id, m->root,
> +					m->mountpoint, m->source);
> +			}
> +			return -1;
> +		}
> +	}
> +
> +	return 0;
>  }
>  
>  static int mnt_tree_for_each_reverse(struct mount_info *m,
>  		int (*fn)(struct mount_info *))
>  {
> -	MNT_TREE_WALK(m, prev, MNT_WALK_NONE, fn);
> +	MNT_TREE_WALK(m, prev, MNT_WALK_NONE, fn, (struct list_head *) NULL);
>  }
>  
>  static char *resolve_source(struct mount_info *mi)
>