Subversion Repositories test_project

/*

 *  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 "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 inline struct vfsmount *first_slave(struct vfsmount *p)

{

        return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);

}

static inline struct vfsmount *next_slave(struct vfsmount *p)

{

        return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);

}

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_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 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;

                if (type == MS_UNBINDABLE)

                        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

 */

static struct vfsmount *propagation_next(struct vfsmount *m,

                                         struct vfsmount *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 vfsmount *next;

                struct vfsmount *master = m->mnt_master;

                if (master == origin->mnt_master) {

                        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;

        }

}

/*

 * return the source mount to be used for cloning

 *

 * @dest        the current destination mount

 * @last_dest   the last seen destination mount

 * @last_src    the last seen source mount

 * @type        return CL_SLAVE if the new mount has to be

 *              cloned as a slave.

 */

static struct vfsmount *get_source(struct vfsmount *dest,

                                        struct vfsmount *last_dest,

                                        struct vfsmount *last_src,

                                        int *type)

{

        struct vfsmount *p_last_src = NULL;

        struct vfsmount *p_last_dest = NULL;

        *type = CL_PROPAGATION;

        if (IS_MNT_SHARED(dest))

                *type |= CL_MAKE_SHARED;

        while (last_dest != dest->mnt_master) {

                p_last_dest = last_dest;

                p_last_src = last_src;

                last_dest = last_dest->mnt_master;

                last_src = last_src->mnt_master;

        }

        if (p_last_dest) {

                do {

                        p_last_dest = next_peer(p_last_dest);

                } while (IS_MNT_NEW(p_last_dest));

        }

        if (dest != p_last_dest) {

                *type |= CL_SLAVE;

                return last_src;

        } else

                return p_last_src;

}

/*

 * 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;

                struct vfsmount *source;

                if (IS_MNT_NEW(m))

                        continue;

                source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type);

                if (!(child = copy_tree(source, source->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_move_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;

}