Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
  [PATCH] mnt_expire is protected by namespace_sem, no need for vfsmount_lock
  [PATCH] do shrink_submounts() for all fs types
  [PATCH] sanitize locking in mark_mounts_for_expiry() and shrink_submounts()
  [PATCH] count ghost references to vfsmounts
  [PATCH] reduce stack footprint in namespace.c

7 files changed, 70 insertions, 145 deletions

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 5ca3625cd39e..9ba16edc0af2 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -573,7 +573,6 @@ extern const struct file_operations afs_mntpt_file_operations;
 
 extern int afs_mntpt_check_symlink(struct afs_vnode *, struct key *);
 extern void afs_mntpt_kill_timer(void);
-extern void afs_umount_begin(struct vfsmount *, int);
 
 /*
  * proc.c
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index a3510b8ba3e7..2f5503902c37 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -283,11 +283,3 @@ void afs_mntpt_kill_timer(void)
         cancel_delayed_work(&afs_mntpt_expiry_timer);
         flush_scheduled_work();
 }
-
-/*
- * begin unmount by attempting to remove all automounted mountpoints we added
- */
-void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
-{
-        shrink_submounts(vfsmnt, &afs_vfsmounts);
-}
diff --git a/fs/afs/super.c b/fs/afs/super.c
index 36bbce45f44b..4b572b801d8d 100644
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -50,7 +50,6 @@ static const struct super_operations afs_super_ops = {
         .write_inode    = afs_write_inode,
         .destroy_inode  = afs_destroy_inode,
         .clear_inode    = afs_clear_inode,
-        .umount_begin   = afs_umount_begin,
         .put_super      = afs_put_super,
         .show_options   = generic_show_options,
 };
diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index a1a95b027136..56c924033b78 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -33,7 +33,6 @@ void dfs_shrink_umount_helper(struct vfsmount *vfsmnt)
 {
         mark_mounts_for_expiry(&cifs_dfs_automount_list);
         mark_mounts_for_expiry(&cifs_dfs_automount_list);
-        shrink_submounts(vfsmnt, &cifs_dfs_automount_list);
 }
 
 /**
diff --git a/fs/namespace.c b/fs/namespace.c
index 7953c96a2071..94f026ec990a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -155,15 +155,15 @@ static void __touch_mnt_namespace(struct mnt_namespace *ns)
         }
 }
 
-static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
+static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
 {
-        old_nd->path.dentry = mnt->mnt_mountpoint;
-        old_nd->path.mnt = mnt->mnt_parent;
+        old_path->dentry = mnt->mnt_mountpoint;
+        old_path->mnt = mnt->mnt_parent;
         mnt->mnt_parent = mnt;
         mnt->mnt_mountpoint = mnt->mnt_root;
         list_del_init(&mnt->mnt_child);
         list_del_init(&mnt->mnt_hash);
-        old_nd->path.dentry->d_mounted--;
+        old_path->dentry->d_mounted--;
 }
 
 void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
@@ -174,12 +174,12 @@ void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
         dentry->d_mounted++;
 }
 
-static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
+static void attach_mnt(struct vfsmount *mnt, struct path *path)
 {
-        mnt_set_mountpoint(nd->path.mnt, nd->path.dentry, mnt);
+        mnt_set_mountpoint(path->mnt, path->dentry, mnt);
         list_add_tail(&mnt->mnt_hash, mount_hashtable +
-                        hash(nd->path.mnt, nd->path.dentry));
-        list_add_tail(&mnt->mnt_child, &nd->path.mnt->mnt_mounts);
+                        hash(path->mnt, path->dentry));
+        list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
 }
 
 /*
@@ -262,10 +262,8 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
                 /* stick the duplicate mount on the same expiry list
                  * as the original if that was on one */
                 if (flag & CL_EXPIRE) {
-                        spin_lock(&vfsmount_lock);
                         if (!list_empty(&old->mnt_expire))
                                 list_add(&mnt->mnt_expire, &old->mnt_expire);
-                        spin_unlock(&vfsmount_lock);
                 }
         }
         return mnt;
@@ -548,6 +546,7 @@ void release_mounts(struct list_head *head)
                         m = mnt->mnt_parent;
                         mnt->mnt_mountpoint = mnt->mnt_root;
                         mnt->mnt_parent = mnt;
+                        m->mnt_ghosts--;
                         spin_unlock(&vfsmount_lock);
                         dput(dentry);
                         mntput(m);
@@ -572,12 +571,16 @@ void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
                 __touch_mnt_namespace(p->mnt_ns);
                 p->mnt_ns = NULL;
                 list_del_init(&p->mnt_child);
-                if (p->mnt_parent != p)
+                if (p->mnt_parent != p) {
+                        p->mnt_parent->mnt_ghosts++;
                         p->mnt_mountpoint->d_mounted--;
+                }
                 change_mnt_propagation(p, MS_PRIVATE);
         }
 }
 
+static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);
+
 static int do_umount(struct vfsmount *mnt, int flags)
 {
         struct super_block *sb = mnt->mnt_sb;
@@ -650,6 +653,9 @@ static int do_umount(struct vfsmount *mnt, int flags)
         spin_lock(&vfsmount_lock);
         event++;
 
+        if (!(flags & MNT_DETACH))
+                shrink_submounts(mnt, &umount_list);
+
         retval = -EBUSY;
         if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
                 if (!list_empty(&mnt->mnt_list))
@@ -744,7 +750,7 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
                                         int flag)
 {
         struct vfsmount *res, *p, *q, *r, *s;
-        struct nameidata nd;
+        struct path path;
 
         if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
                 return NULL;
@@ -769,14 +775,14 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
                                 q = q->mnt_parent;
                         }
                         p = s;
-                        nd.path.mnt = q;
-                        nd.path.dentry = p->mnt_mountpoint;
+                        path.mnt = q;
+                        path.dentry = p->mnt_mountpoint;
                         q = clone_mnt(p, p->mnt_root, flag);
                         if (!q)
                                 goto Enomem;
                         spin_lock(&vfsmount_lock);
                         list_add_tail(&q->mnt_list, &res->mnt_list);
-                        attach_mnt(q, &nd);
+                        attach_mnt(q, &path);
                         spin_unlock(&vfsmount_lock);
                 }
         }
@@ -876,11 +882,11 @@ void drop_collected_mounts(struct vfsmount *mnt)
  * in allocations.
  */
 static int attach_recursive_mnt(struct vfsmount *source_mnt,
-                        struct nameidata *nd, struct nameidata *parent_nd)
+                        struct path *path, struct path *parent_path)
 {
         LIST_HEAD(tree_list);
-        struct vfsmount *dest_mnt = nd->path.mnt;
-        struct dentry *dest_dentry = nd->path.dentry;
+        struct vfsmount *dest_mnt = path->mnt;
+        struct dentry *dest_dentry = path->dentry;
         struct vfsmount *child, *p;
 
         if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
@@ -892,9 +898,9 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
         }
 
         spin_lock(&vfsmount_lock);
-        if (parent_nd) {
-                detach_mnt(source_mnt, parent_nd);
-                attach_mnt(source_mnt, nd);
+        if (parent_path) {
+                detach_mnt(source_mnt, parent_path);
+                attach_mnt(source_mnt, path);
                 touch_mnt_namespace(current->nsproxy->mnt_ns);
         } else {
                 mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
@@ -930,7 +936,7 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
 
         err = -ENOENT;
         if (IS_ROOT(nd->path.dentry) || !d_unhashed(nd->path.dentry))
-                err = attach_recursive_mnt(mnt, nd, NULL);
+                err = attach_recursive_mnt(mnt, &nd->path, NULL);
 out_unlock:
         mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
         if (!err)
@@ -1059,7 +1065,8 @@ static inline int tree_contains_unbindable(struct vfsmount *mnt)
  */
 static noinline int do_move_mount(struct nameidata *nd, char *old_name)
 {
-        struct nameidata old_nd, parent_nd;
+        struct nameidata old_nd;
+        struct path parent_path;
         struct vfsmount *p;
         int err = 0;
         if (!capable(CAP_SYS_ADMIN))
@@ -1114,21 +1121,19 @@ static noinline int do_move_mount(struct nameidata *nd, char *old_name)
                 if (p == old_nd.path.mnt)
                         goto out1;
 
-        err = attach_recursive_mnt(old_nd.path.mnt, nd, &parent_nd);
+        err = attach_recursive_mnt(old_nd.path.mnt, &nd->path, &parent_path);
         if (err)
                 goto out1;
 
-        spin_lock(&vfsmount_lock);
         /* if the mount is moved, it should no longer be expire
          * automatically */
         list_del_init(&old_nd.path.mnt->mnt_expire);
-        spin_unlock(&vfsmount_lock);
 out1:
         mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
 out:
         up_write(&namespace_sem);
         if (!err)
-                path_put(&parent_nd.path);
+                path_put(&parent_path);
         path_put(&old_nd.path);
         return err;
 }
@@ -1189,12 +1194,9 @@ int do_add_mount(struct vfsmount *newmnt, struct nameidata *nd,
         if ((err = graft_tree(newmnt, nd)))
                 goto unlock;
 
-        if (fslist) {
-                /* add to the specified expiration list */
-                spin_lock(&vfsmount_lock);
+        if (fslist) /* add to the specified expiration list */
                 list_add_tail(&newmnt->mnt_expire, fslist);
-                spin_unlock(&vfsmount_lock);
-        }
+
         up_write(&namespace_sem);
         return 0;
 
@@ -1206,75 +1208,6 @@ unlock:
 
 EXPORT_SYMBOL_GPL(do_add_mount);
 
-static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
-                                struct list_head *umounts)
-{
-        spin_lock(&vfsmount_lock);
-
-        /*
-         * Check if mount is still attached, if not, let whoever holds it deal
-         * with the sucker
-         */
-        if (mnt->mnt_parent == mnt) {
-                spin_unlock(&vfsmount_lock);
-                return;
-        }
-
-        /*
-         * Check that it is still dead: the count should now be 2 - as
-         * contributed by the vfsmount parent and the mntget above
-         */
-        if (!propagate_mount_busy(mnt, 2)) {
-                /* delete from the namespace */
-                touch_mnt_namespace(mnt->mnt_ns);
-                list_del_init(&mnt->mnt_list);
-                mnt->mnt_ns = NULL;
-                umount_tree(mnt, 1, umounts);
-                spin_unlock(&vfsmount_lock);
-        } else {
-                /*
-                 * Someone brought it back to life whilst we didn't have any
-                 * locks held so return it to the expiration list
-                 */
-                list_add_tail(&mnt->mnt_expire, mounts);
-                spin_unlock(&vfsmount_lock);
-        }
-}
-
-/*
- * go through the vfsmounts we've just consigned to the graveyard to
- * - check that they're still dead
- * - delete the vfsmount from the appropriate namespace under lock
- * - dispose of the corpse
- */
-static void expire_mount_list(struct list_head *graveyard, struct list_head *mounts)
-{
-        struct mnt_namespace *ns;
-        struct vfsmount *mnt;
-
-        while (!list_empty(graveyard)) {
-                LIST_HEAD(umounts);
-                mnt = list_first_entry(graveyard, struct vfsmount, mnt_expire);
-                list_del_init(&mnt->mnt_expire);
-
-                /* don't do anything if the namespace is dead - all the
-                 * vfsmounts from it are going away anyway */
-                ns = mnt->mnt_ns;
-                if (!ns || !ns->root)
-                        continue;
-                get_mnt_ns(ns);
-
-                spin_unlock(&vfsmount_lock);
-                down_write(&namespace_sem);
-                expire_mount(mnt, mounts, &umounts);
-                up_write(&namespace_sem);
-                release_mounts(&umounts);
-                mntput(mnt);
-                put_mnt_ns(ns);
-                spin_lock(&vfsmount_lock);
-        }
-}
-
 /*
  * process a list of expirable mountpoints with the intent of discarding any
  * mountpoints that aren't in use and haven't been touched since last we came
@@ -1284,10 +1217,12 @@ void mark_mounts_for_expiry(struct list_head *mounts)
 {
         struct vfsmount *mnt, *next;
         LIST_HEAD(graveyard);
+        LIST_HEAD(umounts);
 
         if (list_empty(mounts))
                 return;
 
+        down_write(&namespace_sem);
         spin_lock(&vfsmount_lock);
 
         /* extract from the expiration list every vfsmount that matches the
@@ -1298,16 +1233,19 @@ void mark_mounts_for_expiry(struct list_head *mounts)
          */
         list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
                 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
-                    atomic_read(&mnt->mnt_count) != 1)
+                        propagate_mount_busy(mnt, 1))
                         continue;
-
-                mntget(mnt);
                 list_move(&mnt->mnt_expire, &graveyard);
         }
-
-        expire_mount_list(&graveyard, mounts);
-
+        while (!list_empty(&graveyard)) {
+                mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
+                touch_mnt_namespace(mnt->mnt_ns);
+                umount_tree(mnt, 1, &umounts);
+        }
         spin_unlock(&vfsmount_lock);
+        up_write(&namespace_sem);
+
+        release_mounts(&umounts);
 }
 
 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
@@ -1343,7 +1281,6 @@ resume:
                 }
 
                 if (!propagate_mount_busy(mnt, 1)) {
-                        mntget(mnt);
                         list_move_tail(&mnt->mnt_expire, graveyard);
                         found++;
                 }
@@ -1363,22 +1300,22 @@ resume:
  * process a list of expirable mountpoints with the intent of discarding any
  * submounts of a specific parent mountpoint
  */
-void shrink_submounts(struct vfsmount *mountpoint, struct list_head *mounts)
+static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
 {
         LIST_HEAD(graveyard);
-        int found;
-
-        spin_lock(&vfsmount_lock);
+        struct vfsmount *m;
 
         /* extract submounts of 'mountpoint' from the expiration list */
-        while ((found = select_submounts(mountpoint, &graveyard)) != 0)
-                expire_mount_list(&graveyard, mounts);
-
-        spin_unlock(&vfsmount_lock);
+        while (select_submounts(mnt, &graveyard)) {
+                while (!list_empty(&graveyard)) {
+                        m = list_first_entry(&graveyard, struct vfsmount,
+                                                mnt_expire);
+                        touch_mnt_namespace(mnt->mnt_ns);
+                        umount_tree(mnt, 1, umounts);
+                }
+        }
 }
 
-EXPORT_SYMBOL_GPL(shrink_submounts);
-
 /*
  * Some copy_from_user() implementations do not return the exact number of
  * bytes remaining to copy on a fault.  But copy_mount_options() requires that.
@@ -1683,7 +1620,7 @@ void set_fs_pwd(struct fs_struct *fs, struct path *path)
                 path_put(&old_pwd);
 }
 
-static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
+static void chroot_fs_refs(struct path *old_root, struct path *new_root)
 {
         struct task_struct *g, *p;
         struct fs_struct *fs;
@@ -1695,12 +1632,12 @@ static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
                 if (fs) {
                         atomic_inc(&fs->count);
                         task_unlock(p);
-                        if (fs->root.dentry == old_nd->path.dentry
-                            && fs->root.mnt == old_nd->path.mnt)
-                                set_fs_root(fs, &new_nd->path);
-                        if (fs->pwd.dentry == old_nd->path.dentry
-                            && fs->pwd.mnt == old_nd->path.mnt)
-                                set_fs_pwd(fs, &new_nd->path);
+                        if (fs->root.dentry == old_root->dentry
+                            && fs->root.mnt == old_root->mnt)
+                                set_fs_root(fs, new_root);
+                        if (fs->pwd.dentry == old_root->dentry
+                            && fs->pwd.mnt == old_root->mnt)
+                                set_fs_pwd(fs, new_root);
                         put_fs_struct(fs);
                 } else
                         task_unlock(p);
@@ -1737,7 +1674,8 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
                                const char __user * put_old)
 {
         struct vfsmount *tmp;
-        struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
+        struct nameidata new_nd, old_nd, user_nd;
+        struct path parent_path, root_parent;
         int error;
 
         if (!capable(CAP_SYS_ADMIN))
@@ -1811,19 +1749,19 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
                         goto out3;
         } else if (!is_subdir(old_nd.path.dentry, new_nd.path.dentry))
                 goto out3;
-        detach_mnt(new_nd.path.mnt, &parent_nd);
+        detach_mnt(new_nd.path.mnt, &parent_path);
         detach_mnt(user_nd.path.mnt, &root_parent);
         /* mount old root on put_old */
-        attach_mnt(user_nd.path.mnt, &old_nd);
+        attach_mnt(user_nd.path.mnt, &old_nd.path);
         /* mount new_root on / */
         attach_mnt(new_nd.path.mnt, &root_parent);
         touch_mnt_namespace(current->nsproxy->mnt_ns);
         spin_unlock(&vfsmount_lock);
-        chroot_fs_refs(&user_nd, &new_nd);
+        chroot_fs_refs(&user_nd.path, &new_nd.path);
         security_sb_post_pivotroot(&user_nd, &new_nd);
         error = 0;
-        path_put(&root_parent.path);
-        path_put(&parent_nd.path);
+        path_put(&root_parent);
+        path_put(&parent_path);
 out2:
         mutex_unlock(&old_nd.path.dentry->d_inode->i_mutex);
         up_write(&namespace_sem);
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index dd4dfcd632ec..f9219024f31a 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -589,8 +589,6 @@ static void nfs_umount_begin(struct vfsmount *vfsmnt, int flags)
         struct nfs_server *server = NFS_SB(vfsmnt->mnt_sb);
         struct rpc_clnt *rpc;
 
-        shrink_submounts(vfsmnt, &nfs_automount_list);
-
         if (!(flags & MNT_FORCE))
                 return;
         /* -EIO all pending I/O */
diff --git a/fs/pnode.c b/fs/pnode.c
index 05ba692bc540..1d8f5447f3f7 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -225,7 +225,7 @@ out:
  */
 static inline int do_refcount_check(struct vfsmount *mnt, int count)
 {
-        int mycount = atomic_read(&mnt->mnt_count);
+        int mycount = atomic_read(&mnt->mnt_count) - mnt->mnt_ghosts;
         return (mycount > count);
 }