"Serge E. Hallyn" <serge@xxxxxxxxxx> writes:
> This is so that userspace can distinguish a mount made in a cgroup
> namespace from a bind mount from a cgroup subdirectory.
To do that do you need to print the path, or is an extra option that
reveals nothing except that it was a cgroup mount sufficient?
Is there any practical difference between a mount in a namespace and a
bind mount?
Given the way the conversation has been going I think it would be good
to see the answers to these questions. Perhaps I missed it but I
haven't seen the answers to those questions.
Eric
>
> Signed-off-by: Serge Hallyn <serge.hallyn@xxxxxxxxxx>
> ---
> Changelog: 2016-04-13: pass kernfs_node rather than dentry to show_options
> ---
> fs/kernfs/mount.c | 2 +-
> include/linux/kernfs.h | 3 ++-
> kernel/cgroup.c | 28 +++++++++++++++++++++++++++-
> 3 files changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
> index f73541f..58e8a86 100644
> --- a/fs/kernfs/mount.c
> +++ b/fs/kernfs/mount.c
> @@ -36,7 +36,7 @@ static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
> struct kernfs_syscall_ops *scops = root->syscall_ops;
>
> if (scops && scops->show_options)
> - return scops->show_options(sf, root);
> + return scops->show_options(sf, dentry->d_fsdata, root);
> return 0;
> }
>
> diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
> index c06c442..72b4081 100644
> --- a/include/linux/kernfs.h
> +++ b/include/linux/kernfs.h
> @@ -145,7 +145,8 @@ struct kernfs_node {
> */
> struct kernfs_syscall_ops {
> int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
> - int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
> + int (*show_options)(struct seq_file *sf, struct kernfs_node *kn,
> + struct kernfs_root *root);
>
> int (*mkdir)(struct kernfs_node *parent, const char *name,
> umode_t mode);
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 671dc05..4d26d07 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1593,7 +1593,31 @@ static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
> return 0;
> }
>
> -static int cgroup_show_options(struct seq_file *seq,
> +static void cgroup_show_nsroot(struct seq_file *seq, struct kernfs_node *knode,
> + struct kernfs_root *kroot)
> +{
> + char *nsroot;
> + int len, ret;
> +
> + if (!kroot)
> + return;
> + len = kernfs_path_from_node(knode, kroot->kn, NULL, 0);
> + if (len <= 0)
> + return;
> + nsroot = kzalloc(len + 1, GFP_ATOMIC);
> + if (!nsroot)
> + return;
> + ret = kernfs_path_from_node(knode, kroot->kn, nsroot, len + 1);
> + if (ret <= 0 || ret > len)
> + goto out;
> +
> + seq_show_option(seq, "nsroot", nsroot);
> +
> +out:
> + kfree(nsroot);
> +}
> +
> +static int cgroup_show_options(struct seq_file *seq, struct kernfs_node *kn,
> struct kernfs_root *kf_root)
> {
> struct cgroup_root *root = cgroup_root_from_kf(kf_root);
> @@ -1619,6 +1643,8 @@ static int cgroup_show_options(struct seq_file *seq,
> seq_puts(seq, ",clone_children");
> if (strlen(root->name))
> seq_show_option(seq, "name", root->name);
> + cgroup_show_nsroot(seq, kn, kf_root);
> +
> return 0;
> }
--
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