[patch 4/7] vfs: mountinfo: add mount peer group ID

[linux-2.6-block.git] / fs / namespace.c

diff --git a/fs/namespace.c b/fs/namespace.c
index 8ca6317cb401b303fde6f3d6fda73b33ecc617d8..cefa1d9939b01a8b8dbbca4da239ee31fcddc7e4 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -41,6 +41,7 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);
 
 static int event;
 static DEFINE_IDA(mnt_id_ida);
+static DEFINE_IDA(mnt_group_ida);
 
 static struct list_head *mount_hashtable __read_mostly;
 static struct kmem_cache *mnt_cache __read_mostly;
@@ -83,6 +84,28 @@ static void mnt_free_id(struct vfsmount *mnt)
        spin_unlock(&vfsmount_lock);
 }
 
+/*
+ * Allocate a new peer group ID
+ *
+ * mnt_group_ida is protected by namespace_sem
+ */
+static int mnt_alloc_group_id(struct vfsmount *mnt)
+{
+       if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
+               return -ENOMEM;
+
+       return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
+}
+
+/*
+ * Release a peer group ID
+ */
+void mnt_release_group_id(struct vfsmount *mnt)
+{
+       ida_remove(&mnt_group_ida, mnt->mnt_group_id);
+       mnt->mnt_group_id = 0;
+}
+
 struct vfsmount *alloc_vfsmnt(const char *name)
 {
        struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
@@ -533,6 +556,17 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
        struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);
 
        if (mnt) {
+               if (flag & (CL_SLAVE | CL_PRIVATE))
+                       mnt->mnt_group_id = 0; /* not a peer of original */
+               else
+                       mnt->mnt_group_id = old->mnt_group_id;
+
+               if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
+                       int err = mnt_alloc_group_id(mnt);
+                       if (err)
+                               goto out_free;
+               }
+
                mnt->mnt_flags = old->mnt_flags;
                atomic_inc(&sb->s_active);
                mnt->mnt_sb = sb;
@@ -562,6 +596,10 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
                }
        }
        return mnt;
+
+ out_free:
+       free_vfsmnt(mnt);
+       return NULL;
 }
 
 static inline void __mntput(struct vfsmount *mnt)
@@ -1142,6 +1180,33 @@ void drop_collected_mounts(struct vfsmount *mnt)
        release_mounts(&umount_list);
 }
 
+static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end)
+{
+       struct vfsmount *p;
+
+       for (p = mnt; p != end; p = next_mnt(p, mnt)) {
+               if (p->mnt_group_id && !IS_MNT_SHARED(p))
+                       mnt_release_group_id(p);
+       }
+}
+
+static int invent_group_ids(struct vfsmount *mnt, bool recurse)
+{
+       struct vfsmount *p;
+
+       for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
+               if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
+                       int err = mnt_alloc_group_id(p);
+                       if (err) {
+                               cleanup_group_ids(mnt, p);
+                               return err;
+                       }
+               }
+       }
+
+       return 0;
+}
+
 /*
  *  @source_mnt : mount tree to be attached
  *  @nd         : place the mount tree @source_mnt is attached
@@ -1212,9 +1277,16 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
        struct vfsmount *dest_mnt = path->mnt;
        struct dentry *dest_dentry = path->dentry;
        struct vfsmount *child, *p;
+       int err;
 
-       if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
-               return -EINVAL;
+       if (IS_MNT_SHARED(dest_mnt)) {
+               err = invent_group_ids(source_mnt, true);
+               if (err)
+                       goto out;
+       }
+       err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list);
+       if (err)
+               goto out_cleanup_ids;
 
        if (IS_MNT_SHARED(dest_mnt)) {
                for (p = source_mnt; p; p = next_mnt(p, source_mnt))
@@ -1237,6 +1309,12 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
        }
        spin_unlock(&vfsmount_lock);
        return 0;
+
+ out_cleanup_ids:
+       if (IS_MNT_SHARED(dest_mnt))
+               cleanup_group_ids(source_mnt, NULL);
+ out:
+       return err;
 }
 
 static int graft_tree(struct vfsmount *mnt, struct path *path)
@@ -1277,6 +1355,7 @@ static noinline int do_change_type(struct nameidata *nd, int flag)
        struct vfsmount *m, *mnt = nd->path.mnt;
        int recurse = flag & MS_REC;
        int type = flag & ~MS_REC;
+       int err = 0;
 
        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
@@ -1285,12 +1364,20 @@ static noinline int do_change_type(struct nameidata *nd, int flag)
                return -EINVAL;
 
        down_write(&namespace_sem);
+       if (type == MS_SHARED) {
+               err = invent_group_ids(mnt, recurse);
+               if (err)
+                       goto out_unlock;
+       }
+
        spin_lock(&vfsmount_lock);
        for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
                change_mnt_propagation(m, type);
        spin_unlock(&vfsmount_lock);
+
+ out_unlock:
        up_write(&namespace_sem);
-       return 0;
+       return err;
 }
 
 /*