[PATCH] shared mounts handling: move
Implement handling of mount --move in presense of shared mounts (see
Documentation/sharedsubtree.txt in the end of patch series for detailed
description).
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/namespace.c b/fs/namespace.c
index 9f5a084..1487982 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -660,7 +660,10 @@
/*
* @source_mnt : mount tree to be attached
- * @nd : place the mount tree @source_mnt is attached
+ * @nd : place the mount tree @source_mnt is attached
+ * @parent_nd : if non-null, detach the source_mnt from its parent and
+ * store the parent mount and mountpoint dentry.
+ * (done when source_mnt is moved)
*
* NOTE: in the table below explains the semantics when a source mount
* of a given type is attached to a destination mount of a given type.
@@ -685,6 +688,21 @@
* (+) the cloned mount is created under the destination mount and is marked
* as shared. The cloned mount is added to the peer group of the source
* mount.
+ * ---------------------------------------------
+ * | MOVE MOUNT OPERATION |
+ * |********************************************
+ * | source-->| shared | private |
+ * | dest | | |
+ * | | | | |
+ * | v | | |
+ * |********************************************
+ * | shared | shared (+) | shared (+) |
+ * | | | |
+ * |non-shared| shared (+*) | private |
+ * *********************************************
+ * (+) the mount is moved to the destination. And is then propagated to all
+ * the mounts in the propagation tree of the destination mount.
+ * (+*) the mount is moved to the destination.
*
* if the source mount is a tree, the operations explained above is
* applied to each mount in the tree.
@@ -692,7 +710,7 @@
* in allocations.
*/
static int attach_recursive_mnt(struct vfsmount *source_mnt,
- struct nameidata *nd)
+ struct nameidata *nd, struct nameidata *parent_nd)
{
LIST_HEAD(tree_list);
struct vfsmount *dest_mnt = nd->mnt;
@@ -708,8 +726,14 @@
}
spin_lock(&vfsmount_lock);
- mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
- commit_tree(source_mnt);
+ if (parent_nd) {
+ detach_mnt(source_mnt, parent_nd);
+ attach_mnt(source_mnt, nd);
+ touch_namespace(current->namespace);
+ } else {
+ mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
+ commit_tree(source_mnt);
+ }
list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
list_del_init(&child->mnt_hash);
@@ -740,7 +764,7 @@
err = -ENOENT;
if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry))
- err = attach_recursive_mnt(mnt, nd);
+ err = attach_recursive_mnt(mnt, nd, NULL);
out_unlock:
up(&nd->dentry->d_inode->i_sem);
if (!err)
@@ -869,35 +893,36 @@
if (IS_DEADDIR(nd->dentry->d_inode))
goto out1;
- spin_lock(&vfsmount_lock);
if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
- goto out2;
+ goto out1;
err = -EINVAL;
if (old_nd.dentry != old_nd.mnt->mnt_root)
- goto out2;
+ goto out1;
if (old_nd.mnt == old_nd.mnt->mnt_parent)
- goto out2;
+ goto out1;
if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
S_ISDIR(old_nd.dentry->d_inode->i_mode))
- goto out2;
-
+ goto out1;
+ /*
+ * Don't move a mount residing in a shared parent.
+ */
+ if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent))
+ goto out1;
err = -ELOOP;
for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
if (p == old_nd.mnt)
- goto out2;
- err = 0;
+ goto out1;
- detach_mnt(old_nd.mnt, &parent_nd);
- attach_mnt(old_nd.mnt, nd);
- touch_namespace(current->namespace);
+ if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd)))
+ goto out1;
+ spin_lock(&vfsmount_lock);
/* if the mount is moved, it should no longer be expire
* automatically */
list_del_init(&old_nd.mnt->mnt_expire);
-out2:
spin_unlock(&vfsmount_lock);
out1:
up(&nd->dentry->d_inode->i_sem);
@@ -1467,6 +1492,10 @@
down_write(&namespace_sem);
down(&old_nd.dentry->d_inode->i_sem);
error = -EINVAL;
+ if (IS_MNT_SHARED(old_nd.mnt) ||
+ IS_MNT_SHARED(new_nd.mnt->mnt_parent) ||
+ IS_MNT_SHARED(user_nd.mnt->mnt_parent))
+ goto out2;
if (!check_mnt(user_nd.mnt))
goto out2;
error = -ENOENT;
