407 lines
10 KiB
C
407 lines
10 KiB
C
/*
|
|
* linux/fs/pnode.c
|
|
*
|
|
* (C) Copyright IBM Corporation 2005.
|
|
* Released under GPL v2.
|
|
* Author : Ram Pai (linuxram@us.ibm.com)
|
|
*
|
|
*/
|
|
#include <linux/mnt_namespace.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/nsproxy.h>
|
|
#include "internal.h"
|
|
#include "pnode.h"
|
|
|
|
/* return the next shared peer mount of @p */
|
|
static inline struct mount *next_peer(struct mount *p)
|
|
{
|
|
return list_entry(p->mnt_share.next, struct mount, mnt_share);
|
|
}
|
|
|
|
static inline struct mount *first_slave(struct mount *p)
|
|
{
|
|
return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
|
|
}
|
|
|
|
static inline struct mount *next_slave(struct mount *p)
|
|
{
|
|
return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
|
|
}
|
|
|
|
static struct mount *get_peer_under_root(struct mount *mnt,
|
|
struct mnt_namespace *ns,
|
|
const struct path *root)
|
|
{
|
|
struct mount *m = mnt;
|
|
|
|
do {
|
|
/* Check the namespace first for optimization */
|
|
if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.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 mount *mnt, const struct path *root)
|
|
{
|
|
struct mount *m;
|
|
|
|
for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
|
|
struct mount *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 mount *mnt)
|
|
{
|
|
struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
|
|
struct mount *slave_mnt;
|
|
|
|
/*
|
|
* slave 'mnt' to a peer mount that has the
|
|
* same root dentry. If none is available then
|
|
* slave it to anything that is available.
|
|
*/
|
|
while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
|
|
peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
|
|
|
|
if (peer_mnt == mnt) {
|
|
peer_mnt = next_peer(mnt);
|
|
if (peer_mnt == mnt)
|
|
peer_mnt = NULL;
|
|
}
|
|
if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
|
|
list_empty(&mnt->mnt_share))
|
|
mnt_release_group_id(mnt);
|
|
|
|
list_del_init(&mnt->mnt_share);
|
|
mnt->mnt_group_id = 0;
|
|
|
|
if (peer_mnt)
|
|
master = peer_mnt;
|
|
|
|
if (master) {
|
|
list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
|
|
slave_mnt->mnt_master = master;
|
|
list_move(&mnt->mnt_slave, &master->mnt_slave_list);
|
|
list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
|
|
INIT_LIST_HEAD(&mnt->mnt_slave_list);
|
|
} else {
|
|
struct list_head *p = &mnt->mnt_slave_list;
|
|
while (!list_empty(p)) {
|
|
slave_mnt = list_first_entry(p,
|
|
struct mount, mnt_slave);
|
|
list_del_init(&slave_mnt->mnt_slave);
|
|
slave_mnt->mnt_master = NULL;
|
|
}
|
|
}
|
|
mnt->mnt_master = master;
|
|
CLEAR_MNT_SHARED(mnt);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
void change_mnt_propagation(struct mount *mnt, int type)
|
|
{
|
|
if (type == MS_SHARED) {
|
|
set_mnt_shared(mnt);
|
|
return;
|
|
}
|
|
do_make_slave(mnt);
|
|
if (type != MS_SLAVE) {
|
|
list_del_init(&mnt->mnt_slave);
|
|
mnt->mnt_master = NULL;
|
|
if (type == MS_UNBINDABLE)
|
|
mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
|
|
else
|
|
mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* get the next mount in the propagation tree.
|
|
* @m: the mount seen last
|
|
* @origin: the original mount from where the tree walk initiated
|
|
*
|
|
* Note that peer groups form contiguous segments of slave lists.
|
|
* We rely on that in get_source() to be able to find out if
|
|
* vfsmount found while iterating with propagation_next() is
|
|
* a peer of one we'd found earlier.
|
|
*/
|
|
static struct mount *propagation_next(struct mount *m,
|
|
struct mount *origin)
|
|
{
|
|
/* are there any slaves of this mount? */
|
|
if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
|
|
return first_slave(m);
|
|
|
|
while (1) {
|
|
struct mount *master = m->mnt_master;
|
|
|
|
if (master == origin->mnt_master) {
|
|
struct mount *next = next_peer(m);
|
|
return (next == origin) ? NULL : next;
|
|
} else if (m->mnt_slave.next != &master->mnt_slave_list)
|
|
return next_slave(m);
|
|
|
|
/* back at master */
|
|
m = master;
|
|
}
|
|
}
|
|
|
|
static struct mount *next_group(struct mount *m, struct mount *origin)
|
|
{
|
|
while (1) {
|
|
while (1) {
|
|
struct mount *next;
|
|
if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
|
|
return first_slave(m);
|
|
next = next_peer(m);
|
|
if (m->mnt_group_id == origin->mnt_group_id) {
|
|
if (next == origin)
|
|
return NULL;
|
|
} else if (m->mnt_slave.next != &next->mnt_slave)
|
|
break;
|
|
m = next;
|
|
}
|
|
/* m is the last peer */
|
|
while (1) {
|
|
struct mount *master = m->mnt_master;
|
|
if (m->mnt_slave.next != &master->mnt_slave_list)
|
|
return next_slave(m);
|
|
m = next_peer(master);
|
|
if (master->mnt_group_id == origin->mnt_group_id)
|
|
break;
|
|
if (master->mnt_slave.next == &m->mnt_slave)
|
|
break;
|
|
m = master;
|
|
}
|
|
if (m == origin)
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
/* all accesses are serialized by namespace_sem */
|
|
static struct user_namespace *user_ns;
|
|
static struct mount *last_dest, *last_source, *dest_master;
|
|
static struct mountpoint *mp;
|
|
static struct hlist_head *list;
|
|
|
|
static int propagate_one(struct mount *m)
|
|
{
|
|
struct mount *child;
|
|
int type;
|
|
/* skip ones added by this propagate_mnt() */
|
|
if (IS_MNT_NEW(m))
|
|
return 0;
|
|
/* skip if mountpoint isn't covered by it */
|
|
if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))
|
|
return 0;
|
|
if (m->mnt_group_id == last_dest->mnt_group_id) {
|
|
type = CL_MAKE_SHARED;
|
|
} else {
|
|
struct mount *n, *p;
|
|
for (n = m; ; n = p) {
|
|
p = n->mnt_master;
|
|
if (p == dest_master || IS_MNT_MARKED(p)) {
|
|
while (last_dest->mnt_master != p) {
|
|
last_source = last_source->mnt_master;
|
|
last_dest = last_source->mnt_parent;
|
|
}
|
|
if (n->mnt_group_id != last_dest->mnt_group_id) {
|
|
last_source = last_source->mnt_master;
|
|
last_dest = last_source->mnt_parent;
|
|
}
|
|
break;
|
|
}
|
|
}
|
|
type = CL_SLAVE;
|
|
/* beginning of peer group among the slaves? */
|
|
if (IS_MNT_SHARED(m))
|
|
type |= CL_MAKE_SHARED;
|
|
}
|
|
|
|
/* Notice when we are propagating across user namespaces */
|
|
if (m->mnt_ns->user_ns != user_ns)
|
|
type |= CL_UNPRIVILEGED;
|
|
child = copy_tree(last_source, last_source->mnt.mnt_root, type);
|
|
if (IS_ERR(child))
|
|
return PTR_ERR(child);
|
|
child->mnt.mnt_flags &= ~MNT_LOCKED;
|
|
mnt_set_mountpoint(m, mp, child);
|
|
last_dest = m;
|
|
last_source = child;
|
|
if (m->mnt_master != dest_master) {
|
|
read_seqlock_excl(&mount_lock);
|
|
SET_MNT_MARK(m->mnt_master);
|
|
read_sequnlock_excl(&mount_lock);
|
|
}
|
|
hlist_add_head(&child->mnt_hash, list);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* mount 'source_mnt' under the destination 'dest_mnt' at
|
|
* dentry 'dest_dentry'. And propagate that mount to
|
|
* all the peer and slave mounts of 'dest_mnt'.
|
|
* Link all the new mounts into a propagation tree headed at
|
|
* source_mnt. Also link all the new mounts using ->mnt_list
|
|
* headed at source_mnt's ->mnt_list
|
|
*
|
|
* @dest_mnt: destination mount.
|
|
* @dest_dentry: destination dentry.
|
|
* @source_mnt: source mount.
|
|
* @tree_list : list of heads of trees to be attached.
|
|
*/
|
|
int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
|
|
struct mount *source_mnt, struct hlist_head *tree_list)
|
|
{
|
|
struct mount *m, *n;
|
|
int ret = 0;
|
|
|
|
/*
|
|
* we don't want to bother passing tons of arguments to
|
|
* propagate_one(); everything is serialized by namespace_sem,
|
|
* so globals will do just fine.
|
|
*/
|
|
user_ns = current->nsproxy->mnt_ns->user_ns;
|
|
last_dest = dest_mnt;
|
|
last_source = source_mnt;
|
|
mp = dest_mp;
|
|
list = tree_list;
|
|
dest_master = dest_mnt->mnt_master;
|
|
|
|
/* all peers of dest_mnt, except dest_mnt itself */
|
|
for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {
|
|
ret = propagate_one(n);
|
|
if (ret)
|
|
goto out;
|
|
}
|
|
|
|
/* all slave groups */
|
|
for (m = next_group(dest_mnt, dest_mnt); m;
|
|
m = next_group(m, dest_mnt)) {
|
|
/* everything in that slave group */
|
|
n = m;
|
|
do {
|
|
ret = propagate_one(n);
|
|
if (ret)
|
|
goto out;
|
|
n = next_peer(n);
|
|
} while (n != m);
|
|
}
|
|
out:
|
|
read_seqlock_excl(&mount_lock);
|
|
hlist_for_each_entry(n, tree_list, mnt_hash) {
|
|
m = n->mnt_parent;
|
|
if (m->mnt_master != dest_mnt->mnt_master)
|
|
CLEAR_MNT_MARK(m->mnt_master);
|
|
}
|
|
read_sequnlock_excl(&mount_lock);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* return true if the refcount is greater than count
|
|
*/
|
|
static inline int do_refcount_check(struct mount *mnt, int count)
|
|
{
|
|
return mnt_get_count(mnt) > count;
|
|
}
|
|
|
|
/*
|
|
* check if the mount 'mnt' can be unmounted successfully.
|
|
* @mnt: the mount to be checked for unmount
|
|
* NOTE: unmounting 'mnt' would naturally propagate to all
|
|
* other mounts its parent propagates to.
|
|
* Check if any of these mounts that **do not have submounts**
|
|
* have more references than 'refcnt'. If so return busy.
|
|
*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
int propagate_mount_busy(struct mount *mnt, int refcnt)
|
|
{
|
|
struct mount *m, *child;
|
|
struct mount *parent = mnt->mnt_parent;
|
|
int ret = 0;
|
|
|
|
if (mnt == parent)
|
|
return do_refcount_check(mnt, refcnt);
|
|
|
|
/*
|
|
* quickly check if the current mount can be unmounted.
|
|
* If not, we don't have to go checking for all other
|
|
* mounts
|
|
*/
|
|
if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
|
|
return 1;
|
|
|
|
for (m = propagation_next(parent, parent); m;
|
|
m = propagation_next(m, parent)) {
|
|
child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);
|
|
if (child && list_empty(&child->mnt_mounts) &&
|
|
(ret = do_refcount_check(child, 1)))
|
|
break;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* NOTE: unmounting 'mnt' naturally propagates to all other mounts its
|
|
* parent propagates to.
|
|
*/
|
|
static void __propagate_umount(struct mount *mnt)
|
|
{
|
|
struct mount *parent = mnt->mnt_parent;
|
|
struct mount *m;
|
|
|
|
BUG_ON(parent == mnt);
|
|
|
|
for (m = propagation_next(parent, parent); m;
|
|
m = propagation_next(m, parent)) {
|
|
|
|
struct mount *child = __lookup_mnt_last(&m->mnt,
|
|
mnt->mnt_mountpoint);
|
|
/*
|
|
* umount the child only if the child has no
|
|
* other children
|
|
*/
|
|
if (child && list_empty(&child->mnt_mounts)) {
|
|
list_del_init(&child->mnt_child);
|
|
hlist_del_init_rcu(&child->mnt_hash);
|
|
hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* collect all mounts that receive propagation from the mount in @list,
|
|
* and return these additional mounts in the same list.
|
|
* @list: the list of mounts to be unmounted.
|
|
*
|
|
* vfsmount lock must be held for write
|
|
*/
|
|
int propagate_umount(struct hlist_head *list)
|
|
{
|
|
struct mount *mnt;
|
|
|
|
hlist_for_each_entry(mnt, list, mnt_hash)
|
|
__propagate_umount(mnt);
|
|
return 0;
|
|
}
|