Commit 97e7e0f7 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro

[patch 7/7] vfs: mountinfo: show dominating group id

Show peer group ID of nearest dominating group that has intersection
with the mount's namespace.
Signed-off-by: default avatarMiklos Szeredi <>
Signed-off-by: default avatarAl Viro <>
parent 2d4d4864
......@@ -2374,8 +2374,14 @@ possible optional fields are:
shared:X mount is shared in peer group X
master:X mount is slave to peer group X
propagate_from:X mount is slave and receives propagation from peer group X (*)
unbindable mount is unbindable
(*) X is the closest dominant peer group under the process's root. If
X is the immediate master of the mount, or if there's no dominant peer
group under the same root, then only the "master:X" field is present
and not the "propagate_from:X" field.
For more information on mount propagation see:
......@@ -850,8 +850,13 @@ static int show_mountinfo(struct seq_file *m, void *v)
/* Tagged fields ("foo:X" or "bar") */
if (IS_MNT_SHARED(mnt))
seq_printf(m, " shared:%i", mnt->mnt_group_id);
if (IS_MNT_SLAVE(mnt))
seq_printf(m, " master:%i", mnt->mnt_master->mnt_group_id);
if (IS_MNT_SLAVE(mnt)) {
int master = mnt->mnt_master->mnt_group_id;
int dom = get_dominating_id(mnt, &p->root);
seq_printf(m, " master:%i", master);
if (dom && dom != master)
seq_printf(m, " propagate_from:%i", dom);
seq_puts(m, " unbindable");
......@@ -28,6 +28,57 @@ static inline struct vfsmount *next_slave(struct vfsmount *p)
return list_entry(p->, struct vfsmount, mnt_slave);
* Return true if path is reachable from root
* namespace_sem is held, and mnt is attached
static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,
const struct path *root)
while (mnt != root->mnt && mnt->mnt_parent != mnt) {
dentry = mnt->mnt_mountpoint;
mnt = mnt->mnt_parent;
return mnt == root->mnt && is_subdir(dentry, root->dentry);
static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,
struct mnt_namespace *ns,
const struct path *root)
struct vfsmount *m = mnt;
do {
/* Check the namespace first for optimization */
if (m->mnt_ns == ns && is_path_reachable(m, m->mnt_root, root))
return m;
m = next_peer(m);
} while (m != mnt);
return NULL;
* Get ID of closest dominating peer group having a representative
* under the given root.
* Caller must hold namespace_sem
int get_dominating_id(struct vfsmount *mnt, const struct path *root)
struct vfsmount *m;
for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
struct vfsmount *d = get_peer_under_root(m, mnt->mnt_ns, root);
if (d)
return d->mnt_group_id;
return 0;
static int do_make_slave(struct vfsmount *mnt)
struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
......@@ -36,4 +36,5 @@ int propagate_mnt(struct vfsmount *, struct dentry *, struct vfsmount *,
int propagate_umount(struct list_head *);
int propagate_mount_busy(struct vfsmount *, int);
void mnt_release_group_id(struct vfsmount *);
int get_dominating_id(struct vfsmount *mnt, const struct path *root);
#endif /* _LINUX_PNODE_H */
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