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/*
* linux/fs/pnode.c
*
* (C) Copyright IBM Corporation 2005.
* Released under GPL v2.
* Author : Ram Pai (linuxram@us.ibm.com)
*
*/
#include <linux/namespace.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include "pnode.h"
/* return the next shared peer mount of @p */
static inline struct vfsmount *next_peer(struct vfsmount *p)
{
return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
}
static int do_make_slave(struct vfsmount *mnt)
{
struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
struct vfsmount *slave_mnt;
/*
* slave 'mnt' to a peer mount that has the
* same root dentry. If none is available than
* slave it to anything that is available.
*/
while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
peer_mnt->mnt_root != mnt->mnt_root) ;
if (peer_mnt == mnt) {
peer_mnt = next_peer(mnt);
if (peer_mnt == mnt)
peer_mnt = NULL;
}
list_del_init(&mnt->mnt_share);
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_del(&mnt->mnt_slave);
list_add(&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_entry(p->next,
struct vfsmount, mnt_slave);
list_del_init(&slave_mnt->mnt_slave);
slave_mnt->mnt_master = NULL;
}
}
mnt->mnt_master = master;
CLEAR_MNT_SHARED(mnt);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
return 0;
}
void change_mnt_propagation(struct vfsmount *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;
}
}
/*
* get the next mount in the propagation tree.
* @m: the mount seen last
* @origin: the original mount from where the tree walk initiated
*/
static struct vfsmount *propagation_next(struct vfsmount *m,
struct vfsmount *origin)
{
m = next_peer(m);
if (m == origin)
return NULL;
return m;
}
/*
* 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 vfsmount *dest_mnt, struct dentry *dest_dentry,
struct vfsmount *source_mnt, struct list_head *tree_list)
{
struct vfsmount *m, *child;
int ret = 0;
struct vfsmount *prev_dest_mnt = dest_mnt;
struct vfsmount *prev_src_mnt = source_mnt;
LIST_HEAD(tmp_list);
LIST_HEAD(umount_list);
for (m = propagation_next(dest_mnt, dest_mnt); m;
m = propagation_next(m, dest_mnt)) {
int type = CL_PROPAGATION;
if (IS_MNT_NEW(m))
continue;
if (IS_MNT_SHARED(m))
type |= CL_MAKE_SHARED;
if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,
type))) {
ret = -ENOMEM;
list_splice(tree_list, tmp_list.prev);
goto out;
}
if (is_subdir(dest_dentry, m->mnt_root)) {
mnt_set_mountpoint(m, dest_dentry, child);
list_add_tail(&child->mnt_hash, tree_list);
} else {
/*
* This can happen if the parent mount was bind mounted
* on some subdirectory of a shared/slave mount.
*/
list_add_tail(&child->mnt_hash, &tmp_list);
}
prev_dest_mnt = m;
prev_src_mnt = child;
}
out:
spin_lock(&vfsmount_lock);
while (!list_empty(&tmp_list)) {
child = list_entry(tmp_list.next, struct vfsmount, mnt_hash);
list_del_init(&child->mnt_hash);
umount_tree(child, 0, &umount_list);
}
spin_unlock(&vfsmount_lock);
release_mounts(&umount_list);
return ret;
}
/*
* return true if the refcount is greater than count
*/
static inline int do_refcount_check(struct vfsmount *mnt, int count)
{
int mycount = atomic_read(&mnt->mnt_count);
return (mycount > 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.
*/
int propagate_mount_busy(struct vfsmount *mnt, int refcnt)
{
struct vfsmount *m, *child;
struct vfsmount *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(m, mnt->mnt_mountpoint, 0);
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 vfsmount *mnt)
{
struct vfsmount *parent = mnt->mnt_parent;
struct vfsmount *m;
BUG_ON(parent == mnt);
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
struct vfsmount *child = __lookup_mnt(m,
mnt->mnt_mountpoint, 0);
/*
* umount the child only if the child has no
* other children
*/
if (child && list_empty(&child->mnt_mounts)) {
list_del(&child->mnt_hash);
list_add_tail(&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.
*/
int propagate_umount(struct list_head *list)
{
struct vfsmount *mnt;
list_for_each_entry(mnt, list, mnt_hash)
__propagate_umount(mnt);
return 0;
}
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