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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/pnode.c
  *
  * (C) Copyright IBM Corporation 2005.
  *  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 <uapi/linux/mount.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 *last_slave(struct mount *p)
 {
     return list_entry(p->mnt_slave_list.prev, 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 *master, *slave_mnt;
 
     if (list_empty(&mnt->mnt_share)) {
         if (IS_MNT_SHARED(mnt)) {
             mnt_release_group_id(mnt);
             CLEAR_MNT_SHARED(mnt);
         }
         master = mnt->mnt_master;
         if (!master) {
             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;
             }
             return 0;
         }
     } else {
         struct mount *m;
         /*
          * slave 'mnt' to a peer mount that has the
          * same root dentry. If none is available then
          * slave it to anything that is available.
          */
         for (m = master = next_peer(mnt); m != mnt; m = next_peer(m)) {
             if (m->mnt.mnt_root == mnt->mnt.mnt_root) {
                 master = m;
                 break;
             }
         }
         list_del_init(&mnt->mnt_share);
         mnt->mnt_group_id = 0;
         CLEAR_MNT_SHARED(mnt);
     }
     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);
     mnt->mnt_master = master;
     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 *skip_propagation_subtree(struct mount *m,
                         struct mount *origin)
 {
     /*
      * Advance m such that propagation_next will not return
      * the slaves of m.
      */
     if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
         m = last_slave(m);
 
     return m;
 }
 
 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 mount *last_dest, *first_source, *last_source, *dest_master;
 static struct mountpoint *mp;
 static struct hlist_head *list;
 
 static inline bool peers(struct mount *m1, struct mount *m2)
 {
     return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
 }
 
 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 (peers(m, last_dest)) {
         type = CL_MAKE_SHARED;
     } else {
         struct mount *n, *p;
         bool done;
         for (n = m; ; n = p) {
             p = n->mnt_master;
             if (p == dest_master || IS_MNT_MARKED(p))
                 break;
         }
         do {
             struct mount *parent = last_source->mnt_parent;
             if (last_source == first_source)
                 break;
             done = parent->mnt_master == p;
             if (done && peers(n, parent))
                 break;
             last_source = last_source->mnt_master;
         } while (!done);
 
         type = CL_SLAVE;
         /* beginning of peer group among the slaves? */
         if (IS_MNT_SHARED(m))
             type |= CL_MAKE_SHARED;
     }
         
     child = copy_tree(last_source, last_source->mnt.mnt_root, type);
     if (IS_ERR(child))
         return PTR_ERR(child);
     read_seqlock_excl(&mount_lock);
     mnt_set_mountpoint(m, mp, child);
     if (m->mnt_master != dest_master)
         SET_MNT_MARK(m->mnt_master);
     read_sequnlock_excl(&mount_lock);
     last_dest = m;
     last_source = child;
     hlist_add_head(&child->mnt_hash, list);
     return count_mounts(m->mnt_ns, child);
 }
 
 /*
  * 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.
      */
     last_dest = dest_mnt;
     first_source = source_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;
 }
 
 static struct mount *find_topper(struct mount *mnt)
 {
     /* If there is exactly one mount covering mnt completely return it. */
     struct mount *child;
 
     if (!list_is_singular(&mnt->mnt_mounts))
         return NULL;
 
     child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child);
     if (child->mnt_mountpoint != mnt->mnt.mnt_root)
         return NULL;
 
     return child;
 }
 
 /*
  * 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, *topper;
     struct mount *parent = mnt->mnt_parent;
 
     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)) {
         int count = 1;
         child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
         if (!child)
             continue;
 
         /* Is there exactly one mount on the child that covers
          * it completely whose reference should be ignored?
          */
         topper = find_topper(child);
         if (topper)
             count += 1;
         else if (!list_empty(&child->mnt_mounts))
             continue;
 
         if (do_refcount_check(child, count))
             return 1;
     }
     return 0;
 }
 
 /*
  * Clear MNT_LOCKED when it can be shown to be safe.
  *
  * mount_lock lock must be held for write
  */
 void propagate_mount_unlock(struct mount *mnt)
 {
     struct mount *parent = mnt->mnt_parent;
     struct mount *m, *child;
 
     BUG_ON(parent == mnt);
 
     for (m = propagation_next(parent, parent); m;
             m = propagation_next(m, parent)) {
         child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint);
         if (child)
             child->mnt.mnt_flags &= ~MNT_LOCKED;
     }
 }
 
 static void umount_one(struct mount *mnt, struct list_head *to_umount)
 {
     CLEAR_MNT_MARK(mnt);
     mnt->mnt.mnt_flags |= MNT_UMOUNT;
     list_del_init(&mnt->mnt_child);
     list_del_init(&mnt->mnt_umounting);
     list_move_tail(&mnt->mnt_list, to_umount);
 }
 
 /*
  * NOTE: unmounting 'mnt' naturally propagates to all other mounts its
  * parent propagates to.
  */
 static bool __propagate_umount(struct mount *mnt,
                    struct list_head *to_umount,
                    struct list_head *to_restore)
 {
     bool progress = false;
     struct mount *child;
 
     /*
      * The state of the parent won't change if this mount is
      * already unmounted or marked as without children.
      */
     if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED))
         goto out;
 
     /* Verify topper is the only grandchild that has not been
      * speculatively unmounted.
      */
     list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
         if (child->mnt_mountpoint == mnt->mnt.mnt_root)
             continue;
         if (!list_empty(&child->mnt_umounting) && IS_MNT_MARKED(child))
             continue;
         /* Found a mounted child */
         goto children;
     }
 
     /* Mark mounts that can be unmounted if not locked */
     SET_MNT_MARK(mnt);
     progress = true;
 
     /* If a mount is without children and not locked umount it. */
     if (!IS_MNT_LOCKED(mnt)) {
         umount_one(mnt, to_umount);
     } else {
 children:
         list_move_tail(&mnt->mnt_umounting, to_restore);
     }
 out:
     return progress;
 }
 
 static void umount_list(struct list_head *to_umount,
             struct list_head *to_restore)
 {
     struct mount *mnt, *child, *tmp;
     list_for_each_entry(mnt, to_umount, mnt_list) {
         list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) {
             /* topper? */
             if (child->mnt_mountpoint == mnt->mnt.mnt_root)
                 list_move_tail(&child->mnt_umounting, to_restore);
             else
                 umount_one(child, to_umount);
         }
     }
 }
 
 static void restore_mounts(struct list_head *to_restore)
 {
     /* Restore mounts to a clean working state */
     while (!list_empty(to_restore)) {
         struct mount *mnt, *parent;
         struct mountpoint *mp;
 
         mnt = list_first_entry(to_restore, struct mount, mnt_umounting);
         CLEAR_MNT_MARK(mnt);
         list_del_init(&mnt->mnt_umounting);
 
         /* Should this mount be reparented? */
         mp = mnt->mnt_mp;
         parent = mnt->mnt_parent;
         while (parent->mnt.mnt_flags & MNT_UMOUNT) {
             mp = parent->mnt_mp;
             parent = parent->mnt_parent;
         }
         if (parent != mnt->mnt_parent)
             mnt_change_mountpoint(parent, mp, mnt);
     }
 }
 
 static void cleanup_umount_visitations(struct list_head *visited)
 {
     while (!list_empty(visited)) {
         struct mount *mnt =
             list_first_entry(visited, struct mount, mnt_umounting);
         list_del_init(&mnt->mnt_umounting);
     }
 }
 
 /*
  * 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 list_head *list)
 {
     struct mount *mnt;
     LIST_HEAD(to_restore);
     LIST_HEAD(to_umount);
     LIST_HEAD(visited);
 
     /* Find candidates for unmounting */
     list_for_each_entry_reverse(mnt, list, mnt_list) {
         struct mount *parent = mnt->mnt_parent;
         struct mount *m;
 
         /*
          * If this mount has already been visited it is known that it's
          * entire peer group and all of their slaves in the propagation
          * tree for the mountpoint has already been visited and there is
          * no need to visit them again.
          */
         if (!list_empty(&mnt->mnt_umounting))
             continue;
 
         list_add_tail(&mnt->mnt_umounting, &visited);
         for (m = propagation_next(parent, parent); m;
              m = propagation_next(m, parent)) {
             struct mount *child = __lookup_mnt(&m->mnt,
                                mnt->mnt_mountpoint);
             if (!child)
                 continue;
 
             if (!list_empty(&child->mnt_umounting)) {
                 /*
                  * If the child has already been visited it is
                  * know that it's entire peer group and all of
                  * their slaves in the propgation tree for the
                  * mountpoint has already been visited and there
                  * is no need to visit this subtree again.
                  */
                 m = skip_propagation_subtree(m, parent);
                 continue;
             } else if (child->mnt.mnt_flags & MNT_UMOUNT) {
                 /*
                  * We have come accross an partially unmounted
                  * mount in list that has not been visited yet.
                  * Remember it has been visited and continue
                  * about our merry way.
                  */
                 list_add_tail(&child->mnt_umounting, &visited);
                 continue;
             }
 
             /* Check the child and parents while progress is made */
             while (__propagate_umount(child,
                           &to_umount, &to_restore)) {
                 /* Is the parent a umount candidate? */
                 child = child->mnt_parent;
                 if (list_empty(&child->mnt_umounting))
                     break;
             }
         }
     }
 
     umount_list(&to_umount, &to_restore);
     restore_mounts(&to_restore);
     cleanup_umount_visitations(&visited);
     list_splice_tail(&to_umount, list);
 
     return 0;
 }

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