[CRIU] [PATCH] mnt: relax constraints on fuse mounts

[Pavel Emelyanov]

On 04/08/2015 09:13 PM, Tycho Andersen wrote:
> 1. If a fuse connection is present, but there are no fuse mounts of that type
>    in the mount namespace, don't refuse to dump.
> 2. If there are mounts of that type in the container but they are external,
>    we're going to bind them anyway, so there's no fuse-specific things that
>    need to be done, so it is safe to dump.
> 
> Signed-off-by: Tycho Andersen <tycho.andersen at canonical.com>
> ---
>  mount.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/mount.c b/mount.c
> index 71c39bf..700c303 100644
> --- a/mount.c
> +++ b/mount.c
> @@ -1024,6 +1024,47 @@ out:
>  	return ret;
>  }
>  
> +static int fusectl_dump(struct mount_info *pm)
> +{
> +	int fd, ret = -1;
> +	struct dirent *de;
> +	DIR *fdir = NULL;
> +
> +	fd = open_mountpoint(pm);
> +	if (fd < 0)
> +		return -1;
> +
> +	fdir = fdopendir(fd);
> +	if (fdir == NULL) {
> +		close(fd);
> +		return -1;
> +	}
> +
> +	while ((de = readdir(fdir))) {
> +		int id;
> +		struct mount_info *it;
> +
> +		if (dir_dots(de))
> +			continue;
> +
> +		if (sscanf(de->d_name, "%d", &id) != 1) {
> +			pr_err("wrong number of items scanned in fusectl dump\n");
> +			goto out;
> +		}
> +
> +		for (it = mntinfo; it; it = it->next) {
> +			if (id == minor(it->s_dev) && !it->external) {

I'm not sure that minor number match is enough. Should we also check the
it->type being fuse?

> +				pr_err("%s is a fuse mount but not external\n", it->mountpoint);
> +				goto out;
> +			}
> +		}
> +	}
> +
> +	ret = 0;
> +out:
> +	closedir(fdir);
> +	return ret;
> +}
>  
>  static int dump_empty_fs(struct mount_info *pm)
>  {
> @@ -1102,7 +1143,7 @@ static struct fstype fstypes[] = {
>  		.code = FSTYPE__SECURITYFS,
>  	}, {
>  		.name = "fusectl",
> -		.dump = dump_empty_fs,
> +		.dump = fusectl_dump,
>  		.code = FSTYPE__FUSECTL,
>  	}, {
>  		.name = "debugfs",
>