1 files changed, 67 insertions, 23 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 2dd333b0fe7f..3dc283fd4716 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -42,6 +42,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 static int event;
 static DEFINE_IDA(mnt_id_ida);
 static DEFINE_IDA(mnt_group_ida);
+static int mnt_id_start = 0;
+static int mnt_group_start = 1;
 
 static struct list_head *mount_hashtable __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
@@ -69,7 +71,9 @@ static int mnt_alloc_id(struct vfsmount *mnt)
 retry:
         ida_pre_get(&mnt_id_ida, GFP_KERNEL);
         spin_lock(&vfsmount_lock);
-        res = ida_get_new(&mnt_id_ida, &mnt->mnt_id);
+        res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
+        if (!res)
+                mnt_id_start = mnt->mnt_id + 1;
         spin_unlock(&vfsmount_lock);
         if (res == -EAGAIN)
                 goto retry;
@@ -79,8 +83,11 @@ retry:
 
 static void mnt_free_id(struct vfsmount *mnt)
 {
+        int id = mnt->mnt_id;
         spin_lock(&vfsmount_lock);
-        ida_remove(&mnt_id_ida, mnt->mnt_id);
+        ida_remove(&mnt_id_ida, id);
+        if (mnt_id_start > id)
+                mnt_id_start = id;
         spin_unlock(&vfsmount_lock);
 }
 
@@ -91,10 +98,18 @@ static void mnt_free_id(struct vfsmount *mnt)
  */
 static int mnt_alloc_group_id(struct vfsmount *mnt)
 {
+        int res;
+
         if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
                 return -ENOMEM;
 
-        return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
+        res = ida_get_new_above(&mnt_group_ida,
+                                mnt_group_start,
+                                &mnt->mnt_group_id);
+        if (!res)
+                mnt_group_start = mnt->mnt_group_id + 1;
+
+        return res;
 }
 
 /*
@@ -102,7 +117,10 @@ static int mnt_alloc_group_id(struct vfsmount *mnt)
  */
 void mnt_release_group_id(struct vfsmount *mnt)
 {
-        ida_remove(&mnt_group_ida, mnt->mnt_group_id);
+        int id = mnt->mnt_group_id;
+        ida_remove(&mnt_group_ida, id);
+        if (mnt_group_start > id)
+                mnt_group_start = id;
         mnt->mnt_group_id = 0;
 }
 
@@ -1937,6 +1955,21 @@ dput_out:
         return retval;
 }
 
+static struct mnt_namespace *alloc_mnt_ns(void)
+{
+        struct mnt_namespace *new_ns;
+
+        new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
+        if (!new_ns)
+                return ERR_PTR(-ENOMEM);
+        atomic_set(&new_ns->count, 1);
+        new_ns->root = NULL;
+        INIT_LIST_HEAD(&new_ns->list);
+        init_waitqueue_head(&new_ns->poll);
+        new_ns->event = 0;
+        return new_ns;
+}
+
 /*
  * Allocate a new namespace structure and populate it with contents
  * copied from the namespace of the passed in task structure.
@@ -1948,14 +1981,9 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
         struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
         struct vfsmount *p, *q;
 
-        new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
-        if (!new_ns)
-                return ERR_PTR(-ENOMEM);
-
-        atomic_set(&new_ns->count, 1);
-        INIT_LIST_HEAD(&new_ns->list);
-        init_waitqueue_head(&new_ns->poll);
-        new_ns->event = 0;
+        new_ns = alloc_mnt_ns();
+        if (IS_ERR(new_ns))
+                return new_ns;
 
         down_write(&namespace_sem);
         /* First pass: copy the tree topology */
@@ -2019,6 +2047,24 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
         return new_ns;
 }
 
+/**
+ * create_mnt_ns - creates a private namespace and adds a root filesystem
+ * @mnt: pointer to the new root filesystem mountpoint
+ */
+struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
+{
+        struct mnt_namespace *new_ns;
+
+        new_ns = alloc_mnt_ns();
+        if (!IS_ERR(new_ns)) {
+                mnt->mnt_ns = new_ns;
+                new_ns->root = mnt;
+                list_add(&new_ns->list, &new_ns->root->mnt_list);
+        }
+        return new_ns;
+}
+EXPORT_SYMBOL(create_mnt_ns);
+
 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
                 char __user *, type, unsigned long, flags, void __user *, data)
 {
@@ -2194,16 +2240,9 @@ static void __init init_mount_tree(void)
         mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
         if (IS_ERR(mnt))
                 panic("Can't create rootfs");
-        ns = kmalloc(sizeof(*ns), GFP_KERNEL);
-        if (!ns)
+        ns = create_mnt_ns(mnt);
+        if (IS_ERR(ns))
                 panic("Can't allocate initial namespace");
-        atomic_set(&ns->count, 1);
-        INIT_LIST_HEAD(&ns->list);
-        init_waitqueue_head(&ns->poll);
-        ns->event = 0;
-        list_add(&mnt->mnt_list, &ns->list);
-        ns->root = mnt;
-        mnt->mnt_ns = ns;
 
         init_task.nsproxy->mnt_ns = ns;
         get_mnt_ns(ns);
@@ -2246,10 +2285,14 @@ void __init mnt_init(void)
         init_mount_tree();
 }
 
-void __put_mnt_ns(struct mnt_namespace *ns)
+void put_mnt_ns(struct mnt_namespace *ns)
 {
-        struct vfsmount *root = ns->root;
+        struct vfsmount *root;
         LIST_HEAD(umount_list);
+
+        if (!atomic_dec_and_lock(&ns->count, &vfsmount_lock))
+                return;
+        root = ns->root;
         ns->root = NULL;
         spin_unlock(&vfsmount_lock);
         down_write(&namespace_sem);
@@ -2260,3 +2303,4 @@ void __put_mnt_ns(struct mnt_namespace *ns)
         release_mounts(&umount_list);
         kfree(ns);
 }
+EXPORT_SYMBOL(put_mnt_ns);