[CRIU] [PATCH 8/9] mounts: handle shared and slave mounts

[Pavel Emelyanov]

On 07/24/2013 12:10 PM, Andrey Vagin wrote:
> The idea is simple. If a mount can't be mounted now, we will try to
> mount it later.
> 
> Signed-off-by: Andrey Vagin <avagin at openvz.org>
> ---
>  mount.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 50 insertions(+), 4 deletions(-)
> 
> diff --git a/mount.c b/mount.c
> index 333b658..8016dcc 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -732,13 +732,33 @@ static int do_new_mount(struct mount_info *mi)
>  {
>  	char *src;
>  	struct fstype *tp = mi->fstype;
> +	struct mount_info *t;
>  
>  	src = resolve_source(mi);
>  	if (!src)
>  		return -1;
>  
> +	/*
> +	 * Wait while all parent are not mounted
> +	 *
> +	 * FIXME a child is shared only between parents,
> +	 * who was present in a moment of birth
> +	 */
> +	if (mi->parent->flags & MS_SHARED) {
> +		list_for_each_entry(t, &mi->parent->mnt_share, mnt_share)
> +			if (!t->mounted) {
> +				pr_debug("Postpone %s due to %s\n", mi->mountpoint, t->mountpoint);
> +				return 1;
> +			}
> +		list_for_each_entry(t, &mi->parent->mnt_slave_list, mnt_slave)
> +			if (!t->mounted) {
> +				pr_debug("Postpone %s\n", mi->mountpoint);
> +				return 1;
> +			}

You umount slaves anyway, presumably this can be skipped.

> +	}
> +
>  	if (mount(src, mi->mountpoint, tp->name,
> -				mi->flags, mi->options) < 0) {
> +			mi->flags & (~MS_SHARED), mi->options) < 0) {
>  		pr_perror("Can't mount at %s", mi->mountpoint);
>  		return -1;
>  	}
> @@ -746,6 +766,8 @@ static int do_new_mount(struct mount_info *mi)
>  	if (restore_shared_options(mi, 0, mi->shared_id, 0))
>  		return -1;
>  
> +	mi->mounted = true;
> +
>  	if (tp->restore && tp->restore(mi))
>  		return -1;
>  
> @@ -754,8 +776,27 @@ static int do_new_mount(struct mount_info *mi)
>  
>  static int do_bind_mount(struct mount_info *mi)
>  {
> -	pr_err("No bind mounts at %s\n", mi->mountpoint);
> -	return -1;
> +	char rpath[PATH_MAX];
> +	bool shared = mi->shared_id && mi->shared_id == mi->bind->shared_id;
> +
> +	snprintf(rpath, sizeof(rpath), "%s%s", mi->bind->mountpoint, mi->root);
> +
> +	pr_info("Bind %s to %s\n", rpath, mi->mountpoint);
> +
> +	if (mount(rpath, mi->mountpoint, NULL,
> +				MS_BIND, NULL) < 0) {
> +		pr_perror("Can't mount at %s", mi->mountpoint);
> +		return -1;
> +	}
> +
> +	if (restore_shared_options(mi, !shared,
> +					mi->shared_id && !shared,
> +					mi->master_id))
> +		return -1;
> +
> +	mi->mounted = true;
> +
> +	return 0;
>  }
>  
>  static inline int fsroot_mounted(struct mount_info *mi)
> @@ -773,9 +814,14 @@ static int do_mount_one(struct mount_info *mi)
>  	if (mi->mounted)
>  		return 0;
>  
> +	if ((mi->master_id || !fsroot_mounted(mi)) && mi->bind == NULL) {
> +		pr_debug("Postpone slave %s\n", mi->mountpoint);
> +		return 1;
> +	}
> +
>  	pr_debug("\tMounting %s @%s\n", mi->fstype->name, mi->mountpoint);
>  
> -	if (fsroot_mounted(mi))
> +	if (!mi->bind)
>  		ret = do_new_mount(mi);
>  	else
>  		ret = do_bind_mount(mi);
>