Commit 21444403 authored by Ram Pai's avatar Ram Pai Committed by Linus Torvalds
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[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: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b90fa9ae
......@@ -660,7 +660,10 @@ Enomem:
/*
* @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 @@ Enomem:
* (+) 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 @@ Enomem:
* 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 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
}
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 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
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 @@ static int do_move_mount(struct nameidata *nd, char *old_name)
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 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
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;
......
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