Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull VFS updates from Al Viro,

Misc cleanups all over the place, mainly wrt /proc interfaces (switch
create_proc_entry to proc_create(), get rid of the deprecated
create_proc_read_entry() in favor of using proc_create_data() and
seq_file etc).

7kloc removed.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits)
  don't bother with deferred freeing of fdtables
  proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h
  proc: Make the PROC_I() and PDE() macros internal to procfs
  proc: Supply a function to remove a proc entry by PDE
  take cgroup_open() and cpuset_open() to fs/proc/base.c
  ppc: Clean up scanlog
  ppc: Clean up rtas_flash driver somewhat
  hostap: proc: Use remove_proc_subtree()
  drm: proc: Use remove_proc_subtree()
  drm: proc: Use minor->index to label things, not PDE->name
  drm: Constify drm_proc_list[]
  zoran: Don't print proc_dir_entry data in debug
  reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show()
  proc: Supply an accessor for getting the data from a PDE's parent
  airo: Use remove_proc_subtree()
  rtl8192u: Don't need to save device proc dir PDE
  rtl8187se: Use a dir under /proc/net/r8180/
  proc: Add proc_mkdir_data()
  proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h}
  proc: Move PDE_NET() to fs/proc/proc_net.c
  ...

1 files changed, 195 insertions, 146 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 341d3f564082..b4f96a5230a3 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -21,7 +21,8 @@
 #include <linux/fs_struct.h>    /* get_fs_root et.al. */
 #include <linux/fsnotify.h>     /* fsnotify_vfsmount_delete */
 #include <linux/uaccess.h>
-#include <linux/proc_fs.h>
+#include <linux/proc_ns.h>
+#include <linux/magic.h>
 #include "pnode.h"
 #include "internal.h"
 
@@ -36,6 +37,7 @@ static int mnt_id_start = 0;
 static int mnt_group_start = 1;
 
 static struct list_head *mount_hashtable __read_mostly;
+static struct list_head *mountpoint_hashtable __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
 static struct rw_semaphore namespace_sem;
 
@@ -605,6 +607,51 @@ struct vfsmount *lookup_mnt(struct path *path)
         }
 }
 
+static struct mountpoint *new_mountpoint(struct dentry *dentry)
+{
+        struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
+        struct mountpoint *mp;
+
+        list_for_each_entry(mp, chain, m_hash) {
+                if (mp->m_dentry == dentry) {
+                        /* might be worth a WARN_ON() */
+                        if (d_unlinked(dentry))
+                                return ERR_PTR(-ENOENT);
+                        mp->m_count++;
+                        return mp;
+                }
+        }
+
+        mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
+        if (!mp)
+                return ERR_PTR(-ENOMEM);
+
+        spin_lock(&dentry->d_lock);
+        if (d_unlinked(dentry)) {
+                spin_unlock(&dentry->d_lock);
+                kfree(mp);
+                return ERR_PTR(-ENOENT);
+        }
+        dentry->d_flags |= DCACHE_MOUNTED;
+        spin_unlock(&dentry->d_lock);
+        mp->m_dentry = dentry;
+        mp->m_count = 1;
+        list_add(&mp->m_hash, chain);
+        return mp;
+}
+
+static void put_mountpoint(struct mountpoint *mp)
+{
+        if (!--mp->m_count) {
+                struct dentry *dentry = mp->m_dentry;
+                spin_lock(&dentry->d_lock);
+                dentry->d_flags &= ~DCACHE_MOUNTED;
+                spin_unlock(&dentry->d_lock);
+                list_del(&mp->m_hash);
+                kfree(mp);
+        }
+}
+
 static inline int check_mnt(struct mount *mnt)
 {
         return mnt->mnt_ns == current->nsproxy->mnt_ns;
@@ -633,27 +680,6 @@ static void __touch_mnt_namespace(struct mnt_namespace *ns)
 }
 
 /*
- * Clear dentry's mounted state if it has no remaining mounts.
- * vfsmount_lock must be held for write.
- */
-static void dentry_reset_mounted(struct dentry *dentry)
-{
-        unsigned u;
-
-        for (u = 0; u < HASH_SIZE; u++) {
-                struct mount *p;
-
-                list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
-                        if (p->mnt_mountpoint == dentry)
-                                return;
-                }
-        }
-        spin_lock(&dentry->d_lock);
-        dentry->d_flags &= ~DCACHE_MOUNTED;
-        spin_unlock(&dentry->d_lock);
-}
-
-/*
  * vfsmount lock must be held for write
  */
 static void detach_mnt(struct mount *mnt, struct path *old_path)
@@ -664,32 +690,35 @@ static void detach_mnt(struct mount *mnt, struct path *old_path)
         mnt->mnt_mountpoint = mnt->mnt.mnt_root;
         list_del_init(&mnt->mnt_child);
         list_del_init(&mnt->mnt_hash);
-        dentry_reset_mounted(old_path->dentry);
+        put_mountpoint(mnt->mnt_mp);
+        mnt->mnt_mp = NULL;
 }
 
 /*
  * vfsmount lock must be held for write
  */
-void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry,
+void mnt_set_mountpoint(struct mount *mnt,
+                        struct mountpoint *mp,
                         struct mount *child_mnt)
 {
+        mp->m_count++;
         mnt_add_count(mnt, 1);  /* essentially, that's mntget */
-        child_mnt->mnt_mountpoint = dget(dentry);
+        child_mnt->mnt_mountpoint = dget(mp->m_dentry);
         child_mnt->mnt_parent = mnt;
-        spin_lock(&dentry->d_lock);
-        dentry->d_flags |= DCACHE_MOUNTED;
-        spin_unlock(&dentry->d_lock);
+        child_mnt->mnt_mp = mp;
 }
 
 /*
  * vfsmount lock must be held for write
  */
-static void attach_mnt(struct mount *mnt, struct path *path)
+static void attach_mnt(struct mount *mnt,
+                        struct mount *parent,
+                        struct mountpoint *mp)
 {
-        mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt);
+        mnt_set_mountpoint(parent, mp, mnt);
         list_add_tail(&mnt->mnt_hash, mount_hashtable +
-                        hash(path->mnt, path->dentry));
-        list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts);
+                        hash(&parent->mnt, mp->m_dentry));
+        list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
 }
 
 /*
@@ -1095,11 +1124,23 @@ int may_umount(struct vfsmount *mnt)
 
 EXPORT_SYMBOL(may_umount);
 
-void release_mounts(struct list_head *head)
+static LIST_HEAD(unmounted);    /* protected by namespace_sem */
+
+static void namespace_unlock(void)
 {
         struct mount *mnt;
-        while (!list_empty(head)) {
-                mnt = list_first_entry(head, struct mount, mnt_hash);
+        LIST_HEAD(head);
+
+        if (likely(list_empty(&unmounted))) {
+                up_write(&namespace_sem);
+                return;
+        }
+
+        list_splice_init(&unmounted, &head);
+        up_write(&namespace_sem);
+
+        while (!list_empty(&head)) {
+                mnt = list_first_entry(&head, struct mount, mnt_hash);
                 list_del_init(&mnt->mnt_hash);
                 if (mnt_has_parent(mnt)) {
                         struct dentry *dentry;
@@ -1119,11 +1160,16 @@ void release_mounts(struct list_head *head)
         }
 }
 
+static inline void namespace_lock(void)
+{
+        down_write(&namespace_sem);
+}
+
 /*
  * vfsmount lock must be held for write
  * namespace_sem must be held for write
  */
-void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
+void umount_tree(struct mount *mnt, int propagate)
 {
         LIST_HEAD(tmp_list);
         struct mount *p;
@@ -1142,20 +1188,20 @@ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill)
                 list_del_init(&p->mnt_child);
                 if (mnt_has_parent(p)) {
                         p->mnt_parent->mnt_ghosts++;
-                        dentry_reset_mounted(p->mnt_mountpoint);
+                        put_mountpoint(p->mnt_mp);
+                        p->mnt_mp = NULL;
                 }
                 change_mnt_propagation(p, MS_PRIVATE);
         }
-        list_splice(&tmp_list, kill);
+        list_splice(&tmp_list, &unmounted);
 }
 
-static void shrink_submounts(struct mount *mnt, struct list_head *umounts);
+static void shrink_submounts(struct mount *mnt);
 
 static int do_umount(struct mount *mnt, int flags)
 {
         struct super_block *sb = mnt->mnt.mnt_sb;
         int retval;
-        LIST_HEAD(umount_list);
 
         retval = security_sb_umount(&mnt->mnt, flags);
         if (retval)
@@ -1222,22 +1268,21 @@ static int do_umount(struct mount *mnt, int flags)
                 return retval;
         }
 
-        down_write(&namespace_sem);
+        namespace_lock();
         br_write_lock(&vfsmount_lock);
         event++;
 
         if (!(flags & MNT_DETACH))
-                shrink_submounts(mnt, &umount_list);
+                shrink_submounts(mnt);
 
         retval = -EBUSY;
         if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
                 if (!list_empty(&mnt->mnt_list))
-                        umount_tree(mnt, 1, &umount_list);
+                        umount_tree(mnt, 1);
                 retval = 0;
         }
         br_write_unlock(&vfsmount_lock);
-        up_write(&namespace_sem);
-        release_mounts(&umount_list);
+        namespace_unlock();
         return retval;
 }
 
@@ -1310,13 +1355,13 @@ static bool mnt_ns_loop(struct path *path)
          * mount namespace loop?
          */
         struct inode *inode = path->dentry->d_inode;
-        struct proc_inode *ei;
+        struct proc_ns *ei;
         struct mnt_namespace *mnt_ns;
 
         if (!proc_ns_inode(inode))
                 return false;
 
-        ei = PROC_I(inode);
+        ei = get_proc_ns(inode);
         if (ei->ns_ops != &mntns_operations)
                 return false;
 
@@ -1327,8 +1372,7 @@ static bool mnt_ns_loop(struct path *path)
 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
                                         int flag)
 {
-        struct mount *res, *p, *q, *r;
-        struct path path;
+        struct mount *res, *p, *q, *r, *parent;
 
         if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
                 return ERR_PTR(-EINVAL);
@@ -1355,25 +1399,22 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
                                 q = q->mnt_parent;
                         }
                         p = s;
-                        path.mnt = &q->mnt;
-                        path.dentry = p->mnt_mountpoint;
+                        parent = q;
                         q = clone_mnt(p, p->mnt.mnt_root, flag);
                         if (IS_ERR(q))
                                 goto out;
                         br_write_lock(&vfsmount_lock);
                         list_add_tail(&q->mnt_list, &res->mnt_list);
-                        attach_mnt(q, &path);
+                        attach_mnt(q, parent, p->mnt_mp);
                         br_write_unlock(&vfsmount_lock);
                 }
         }
         return res;
 out:
         if (res) {
-                LIST_HEAD(umount_list);
                 br_write_lock(&vfsmount_lock);
-                umount_tree(res, 0, &umount_list);
+                umount_tree(res, 0);
                 br_write_unlock(&vfsmount_lock);
-                release_mounts(&umount_list);
         }
         return q;
 }
@@ -1383,10 +1424,10 @@ out:
 struct vfsmount *collect_mounts(struct path *path)
 {
         struct mount *tree;
-        down_write(&namespace_sem);
+        namespace_lock();
         tree = copy_tree(real_mount(path->mnt), path->dentry,
                          CL_COPY_ALL | CL_PRIVATE);
-        up_write(&namespace_sem);
+        namespace_unlock();
         if (IS_ERR(tree))
                 return NULL;
         return &tree->mnt;
@@ -1394,13 +1435,11 @@ struct vfsmount *collect_mounts(struct path *path)
 
 void drop_collected_mounts(struct vfsmount *mnt)
 {
-        LIST_HEAD(umount_list);
-        down_write(&namespace_sem);
+        namespace_lock();
         br_write_lock(&vfsmount_lock);
-        umount_tree(real_mount(mnt), 0, &umount_list);
+        umount_tree(real_mount(mnt), 0);
         br_write_unlock(&vfsmount_lock);
-        up_write(&namespace_sem);
-        release_mounts(&umount_list);
+        namespace_unlock();
 }
 
 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
@@ -1509,11 +1548,11 @@ static int invent_group_ids(struct mount *mnt, bool recurse)
  * in allocations.
  */
 static int attach_recursive_mnt(struct mount *source_mnt,
-                        struct path *path, struct path *parent_path)
+                        struct mount *dest_mnt,
+                        struct mountpoint *dest_mp,
+                        struct path *parent_path)
 {
         LIST_HEAD(tree_list);
-        struct mount *dest_mnt = real_mount(path->mnt);
-        struct dentry *dest_dentry = path->dentry;
         struct mount *child, *p;
         int err;
 
@@ -1522,7 +1561,7 @@ static int attach_recursive_mnt(struct mount *source_mnt,
                 if (err)
                         goto out;
         }
-        err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
+        err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
         if (err)
                 goto out_cleanup_ids;
 
@@ -1534,10 +1573,10 @@ static int attach_recursive_mnt(struct mount *source_mnt,
         }
         if (parent_path) {
                 detach_mnt(source_mnt, parent_path);
-                attach_mnt(source_mnt, path);
+                attach_mnt(source_mnt, dest_mnt, dest_mp);
                 touch_mnt_namespace(source_mnt->mnt_ns);
         } else {
-                mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
+                mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
                 commit_tree(source_mnt);
         }
 
@@ -1556,46 +1595,53 @@ static int attach_recursive_mnt(struct mount *source_mnt,
         return err;
 }
 
-static int lock_mount(struct path *path)
+static struct mountpoint *lock_mount(struct path *path)
 {
         struct vfsmount *mnt;
+        struct dentry *dentry = path->dentry;
 retry:
-        mutex_lock(&path->dentry->d_inode->i_mutex);
-        if (unlikely(cant_mount(path->dentry))) {
-                mutex_unlock(&path->dentry->d_inode->i_mutex);
-                return -ENOENT;
+        mutex_lock(&dentry->d_inode->i_mutex);
+        if (unlikely(cant_mount(dentry))) {
+                mutex_unlock(&dentry->d_inode->i_mutex);
+                return ERR_PTR(-ENOENT);
         }
-        down_write(&namespace_sem);
+        namespace_lock();
         mnt = lookup_mnt(path);
-        if (likely(!mnt))
-                return 0;
-        up_write(&namespace_sem);
+        if (likely(!mnt)) {
+                struct mountpoint *mp = new_mountpoint(dentry);
+                if (IS_ERR(mp)) {
+                        namespace_unlock();
+                        mutex_unlock(&dentry->d_inode->i_mutex);
+                        return mp;
+                }
+                return mp;
+        }
+        namespace_unlock();
         mutex_unlock(&path->dentry->d_inode->i_mutex);
         path_put(path);
         path->mnt = mnt;
-        path->dentry = dget(mnt->mnt_root);
+        dentry = path->dentry = dget(mnt->mnt_root);
         goto retry;
 }
 
-static void unlock_mount(struct path *path)
+static void unlock_mount(struct mountpoint *where)
 {
-        up_write(&namespace_sem);
-        mutex_unlock(&path->dentry->d_inode->i_mutex);
+        struct dentry *dentry = where->m_dentry;
+        put_mountpoint(where);
+        namespace_unlock();
+        mutex_unlock(&dentry->d_inode->i_mutex);
 }
 
-static int graft_tree(struct mount *mnt, struct path *path)
+static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
 {
         if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
                 return -EINVAL;
 
-        if (S_ISDIR(path->dentry->d_inode->i_mode) !=
+        if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
               S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
                 return -ENOTDIR;
 
-        if (d_unlinked(path->dentry))
-                return -ENOENT;
-
-        return attach_recursive_mnt(mnt, path, NULL);
+        return attach_recursive_mnt(mnt, p, mp, NULL);
 }
 
 /*
@@ -1633,7 +1679,7 @@ static int do_change_type(struct path *path, int flag)
         if (!type)
                 return -EINVAL;
 
-        down_write(&namespace_sem);
+        namespace_lock();
         if (type == MS_SHARED) {
                 err = invent_group_ids(mnt, recurse);
                 if (err)
@@ -1646,7 +1692,7 @@ static int do_change_type(struct path *path, int flag)
         br_write_unlock(&vfsmount_lock);
 
  out_unlock:
-        up_write(&namespace_sem);
+        namespace_unlock();
         return err;
 }
 
@@ -1656,9 +1702,9 @@ static int do_change_type(struct path *path, int flag)
 static int do_loopback(struct path *path, const char *old_name,
                                 int recurse)
 {
-        LIST_HEAD(umount_list);
         struct path old_path;
-        struct mount *mnt = NULL, *old;
+        struct mount *mnt = NULL, *old, *parent;
+        struct mountpoint *mp;
         int err;
         if (!old_name || !*old_name)
                 return -EINVAL;
@@ -1670,17 +1716,19 @@ static int do_loopback(struct path *path, const char *old_name,
         if (mnt_ns_loop(&old_path))
                 goto out; 
 
-        err = lock_mount(path);
-        if (err)
+        mp = lock_mount(path);
+        err = PTR_ERR(mp);
+        if (IS_ERR(mp))
                 goto out;
 
         old = real_mount(old_path.mnt);
+        parent = real_mount(path->mnt);
 
         err = -EINVAL;
         if (IS_MNT_UNBINDABLE(old))
                 goto out2;
 
-        if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old))
+        if (!check_mnt(parent) || !check_mnt(old))
                 goto out2;
 
         if (recurse)
@@ -1693,15 +1741,14 @@ static int do_loopback(struct path *path, const char *old_name,
                 goto out2;
         }
 
-        err = graft_tree(mnt, path);
+        err = graft_tree(mnt, parent, mp);
         if (err) {
                 br_write_lock(&vfsmount_lock);
-                umount_tree(mnt, 0, &umount_list);
+                umount_tree(mnt, 0);
                 br_write_unlock(&vfsmount_lock);
         }
 out2:
-        unlock_mount(path);
-        release_mounts(&umount_list);
+        unlock_mount(mp);
 out:
         path_put(&old_path);
         return err;
@@ -1786,6 +1833,7 @@ static int do_move_mount(struct path *path, const char *old_name)
         struct path old_path, parent_path;
         struct mount *p;
         struct mount *old;
+        struct mountpoint *mp;
         int err;
         if (!old_name || !*old_name)
                 return -EINVAL;
@@ -1793,8 +1841,9 @@ static int do_move_mount(struct path *path, const char *old_name)
         if (err)
                 return err;
 
-        err = lock_mount(path);
-        if (err < 0)
+        mp = lock_mount(path);
+        err = PTR_ERR(mp);
+        if (IS_ERR(mp))
                 goto out;
 
         old = real_mount(old_path.mnt);
@@ -1804,9 +1853,6 @@ static int do_move_mount(struct path *path, const char *old_name)
         if (!check_mnt(p) || !check_mnt(old))
                 goto out1;
 
-        if (d_unlinked(path->dentry))
-                goto out1;
-
         err = -EINVAL;
         if (old_path.dentry != old_path.mnt->mnt_root)
                 goto out1;
@@ -1833,7 +1879,7 @@ static int do_move_mount(struct path *path, const char *old_name)
                 if (p == old)
                         goto out1;
 
-        err = attach_recursive_mnt(old, path, &parent_path);
+        err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
         if (err)
                 goto out1;
 
@@ -1841,7 +1887,7 @@ static int do_move_mount(struct path *path, const char *old_name)
          * automatically */
         list_del_init(&old->mnt_expire);
 out1:
-        unlock_mount(path);
+        unlock_mount(mp);
 out:
         if (!err)
                 path_put(&parent_path);
@@ -1877,21 +1923,24 @@ static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
  */
 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
 {
+        struct mountpoint *mp;
+        struct mount *parent;
         int err;
 
         mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
 
-        err = lock_mount(path);
-        if (err)
-                return err;
+        mp = lock_mount(path);
+        if (IS_ERR(mp))
+                return PTR_ERR(mp);
 
+        parent = real_mount(path->mnt);
         err = -EINVAL;
-        if (unlikely(!check_mnt(real_mount(path->mnt)))) {
+        if (unlikely(!check_mnt(parent))) {
                 /* that's acceptable only for automounts done in private ns */
                 if (!(mnt_flags & MNT_SHRINKABLE))
                         goto unlock;
                 /* ... and for those we'd better have mountpoint still alive */
-                if (!real_mount(path->mnt)->mnt_ns)
+                if (!parent->mnt_ns)
                         goto unlock;
         }
 
@@ -1906,10 +1955,10 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
                 goto unlock;
 
         newmnt->mnt.mnt_flags = mnt_flags;
-        err = graft_tree(newmnt, path);
+        err = graft_tree(newmnt, parent, mp);
 
 unlock:
-        unlock_mount(path);
+        unlock_mount(mp);
         return err;
 }
 
@@ -1982,11 +2031,11 @@ int finish_automount(struct vfsmount *m, struct path *path)
 fail:
         /* remove m from any expiration list it may be on */
         if (!list_empty(&mnt->mnt_expire)) {
-                down_write(&namespace_sem);
+                namespace_lock();
                 br_write_lock(&vfsmount_lock);
                 list_del_init(&mnt->mnt_expire);
                 br_write_unlock(&vfsmount_lock);
-                up_write(&namespace_sem);
+                namespace_unlock();
         }
         mntput(m);
         mntput(m);
@@ -2000,13 +2049,13 @@ fail:
  */
 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
 {
-        down_write(&namespace_sem);
+        namespace_lock();
         br_write_lock(&vfsmount_lock);
 
         list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
 
         br_write_unlock(&vfsmount_lock);
-        up_write(&namespace_sem);
+        namespace_unlock();
 }
 EXPORT_SYMBOL(mnt_set_expiry);
 
@@ -2019,12 +2068,11 @@ void mark_mounts_for_expiry(struct list_head *mounts)
 {
         struct mount *mnt, *next;
         LIST_HEAD(graveyard);
-        LIST_HEAD(umounts);
 
         if (list_empty(mounts))
                 return;
 
-        down_write(&namespace_sem);
+        namespace_lock();
         br_write_lock(&vfsmount_lock);
 
         /* extract from the expiration list every vfsmount that matches the
@@ -2042,12 +2090,10 @@ void mark_mounts_for_expiry(struct list_head *mounts)
         while (!list_empty(&graveyard)) {
                 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
                 touch_mnt_namespace(mnt->mnt_ns);
-                umount_tree(mnt, 1, &umounts);
+                umount_tree(mnt, 1);
         }
         br_write_unlock(&vfsmount_lock);
-        up_write(&namespace_sem);
-
-        release_mounts(&umounts);
+        namespace_unlock();
 }
 
 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
@@ -2104,7 +2150,7 @@ resume:
  *
  * vfsmount_lock must be held for write
  */
-static void shrink_submounts(struct mount *mnt, struct list_head *umounts)
+static void shrink_submounts(struct mount *mnt)
 {
         LIST_HEAD(graveyard);
         struct mount *m;
@@ -2115,7 +2161,7 @@ static void shrink_submounts(struct mount *mnt, struct list_head *umounts)
                         m = list_first_entry(&graveyard, struct mount,
                                                 mnt_expire);
                         touch_mnt_namespace(m->mnt_ns);
-                        umount_tree(m, 1, umounts);
+                        umount_tree(m, 1);
                 }
         }
 }
@@ -2342,14 +2388,14 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         if (IS_ERR(new_ns))
                 return new_ns;
 
-        down_write(&namespace_sem);
+        namespace_lock();
         /* First pass: copy the tree topology */
         copy_flags = CL_COPY_ALL | CL_EXPIRE;
         if (user_ns != mnt_ns->user_ns)
                 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
         new = copy_tree(old, old->mnt.mnt_root, copy_flags);
         if (IS_ERR(new)) {
-                up_write(&namespace_sem);
+                namespace_unlock();
                 free_mnt_ns(new_ns);
                 return ERR_CAST(new);
         }
@@ -2380,7 +2426,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
                 p = next_mnt(p, old);
                 q = next_mnt(q, new);
         }
-        up_write(&namespace_sem);
+        namespace_unlock();
 
         if (rootmnt)
                 mntput(rootmnt);
@@ -2550,7 +2596,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
                 const char __user *, put_old)
 {
         struct path new, old, parent_path, root_parent, root;
-        struct mount *new_mnt, *root_mnt;
+        struct mount *new_mnt, *root_mnt, *old_mnt;
+        struct mountpoint *old_mp, *root_mp;
         int error;
 
         if (!may_mount())
@@ -2569,14 +2616,16 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
                 goto out2;
 
         get_fs_root(current->fs, &root);
-        error = lock_mount(&old);
-        if (error)
+        old_mp = lock_mount(&old);
+        error = PTR_ERR(old_mp);
+        if (IS_ERR(old_mp))
                 goto out3;
 
         error = -EINVAL;
         new_mnt = real_mount(new.mnt);
         root_mnt = real_mount(root.mnt);
-        if (IS_MNT_SHARED(real_mount(old.mnt)) ||
+        old_mnt = real_mount(old.mnt);
+        if (IS_MNT_SHARED(old_mnt) ||
                 IS_MNT_SHARED(new_mnt->mnt_parent) ||
                 IS_MNT_SHARED(root_mnt->mnt_parent))
                 goto out4;
@@ -2585,37 +2634,37 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
         error = -ENOENT;
         if (d_unlinked(new.dentry))
                 goto out4;
-        if (d_unlinked(old.dentry))
-                goto out4;
         error = -EBUSY;
-        if (new.mnt == root.mnt ||
-            old.mnt == root.mnt)
+        if (new_mnt == root_mnt || old_mnt == root_mnt)
                 goto out4; /* loop, on the same file system  */
         error = -EINVAL;
         if (root.mnt->mnt_root != root.dentry)
                 goto out4; /* not a mountpoint */
         if (!mnt_has_parent(root_mnt))
                 goto out4; /* not attached */
+        root_mp = root_mnt->mnt_mp;
         if (new.mnt->mnt_root != new.dentry)
                 goto out4; /* not a mountpoint */
         if (!mnt_has_parent(new_mnt))
                 goto out4; /* not attached */
         /* make sure we can reach put_old from new_root */
-        if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new))
+        if (!is_path_reachable(old_mnt, old.dentry, &new))
                 goto out4;
+        root_mp->m_count++; /* pin it so it won't go away */
         br_write_lock(&vfsmount_lock);
         detach_mnt(new_mnt, &parent_path);
         detach_mnt(root_mnt, &root_parent);
         /* mount old root on put_old */
-        attach_mnt(root_mnt, &old);
+        attach_mnt(root_mnt, old_mnt, old_mp);
         /* mount new_root on / */
-        attach_mnt(new_mnt, &root_parent);
+        attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
         touch_mnt_namespace(current->nsproxy->mnt_ns);
         br_write_unlock(&vfsmount_lock);
         chroot_fs_refs(&root, &new);
+        put_mountpoint(root_mp);
         error = 0;
 out4:
-        unlock_mount(&old);
+        unlock_mount(old_mp);
         if (!error) {
                 path_put(&root_parent);
                 path_put(&parent_path);
@@ -2670,14 +2719,17 @@ void __init mnt_init(void)
                         0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
 
         mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
+        mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
 
-        if (!mount_hashtable)
+        if (!mount_hashtable || !mountpoint_hashtable)
                 panic("Failed to allocate mount hash table\n");
 
         printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
 
         for (u = 0; u < HASH_SIZE; u++)
                 INIT_LIST_HEAD(&mount_hashtable[u]);
+        for (u = 0; u < HASH_SIZE; u++)
+                INIT_LIST_HEAD(&mountpoint_hashtable[u]);
 
         br_lock_init(&vfsmount_lock);
 
@@ -2694,16 +2746,13 @@ void __init mnt_init(void)
 
 void put_mnt_ns(struct mnt_namespace *ns)
 {
-        LIST_HEAD(umount_list);
-
         if (!atomic_dec_and_test(&ns->count))
                 return;
-        down_write(&namespace_sem);
+        namespace_lock();
         br_write_lock(&vfsmount_lock);
-        umount_tree(ns->root, 0, &umount_list);
+        umount_tree(ns->root, 0);
         br_write_unlock(&vfsmount_lock);
-        up_write(&namespace_sem);
-        release_mounts(&umount_list);
+        namespace_unlock();
         free_mnt_ns(ns);
 }