Commit 21444403 authored by Ram Pai's avatar Ram Pai Committed by Linus Torvalds

[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
...@@ -661,6 +661,9 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, ...@@ -661,6 +661,9 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
/* /*
* @source_mnt : mount tree to be attached * @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 * 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. * of a given type is attached to a destination mount of a given type.
...@@ -685,6 +688,21 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, ...@@ -685,6 +688,21 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
* (+) the cloned mount is created under the destination mount and is marked * (+) 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 * as shared. The cloned mount is added to the peer group of the source
* mount. * 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 * if the source mount is a tree, the operations explained above is
* applied to each mount in the tree. * applied to each mount in the tree.
...@@ -692,7 +710,7 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, ...@@ -692,7 +710,7 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
* in allocations. * in allocations.
*/ */
static int attach_recursive_mnt(struct vfsmount *source_mnt, static int attach_recursive_mnt(struct vfsmount *source_mnt,
struct nameidata *nd) struct nameidata *nd, struct nameidata *parent_nd)
{ {
LIST_HEAD(tree_list); LIST_HEAD(tree_list);
struct vfsmount *dest_mnt = nd->mnt; struct vfsmount *dest_mnt = nd->mnt;
...@@ -708,8 +726,14 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt, ...@@ -708,8 +726,14 @@ static int attach_recursive_mnt(struct vfsmount *source_mnt,
} }
spin_lock(&vfsmount_lock); spin_lock(&vfsmount_lock);
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); mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
commit_tree(source_mnt); commit_tree(source_mnt);
}
list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
list_del_init(&child->mnt_hash); list_del_init(&child->mnt_hash);
...@@ -740,7 +764,7 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd) ...@@ -740,7 +764,7 @@ static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
err = -ENOENT; err = -ENOENT;
if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry)) if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry))
err = attach_recursive_mnt(mnt, nd); err = attach_recursive_mnt(mnt, nd, NULL);
out_unlock: out_unlock:
up(&nd->dentry->d_inode->i_sem); up(&nd->dentry->d_inode->i_sem);
if (!err) if (!err)
...@@ -869,35 +893,36 @@ static int do_move_mount(struct nameidata *nd, char *old_name) ...@@ -869,35 +893,36 @@ static int do_move_mount(struct nameidata *nd, char *old_name)
if (IS_DEADDIR(nd->dentry->d_inode)) if (IS_DEADDIR(nd->dentry->d_inode))
goto out1; goto out1;
spin_lock(&vfsmount_lock);
if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry)) if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
goto out2; goto out1;
err = -EINVAL; err = -EINVAL;
if (old_nd.dentry != old_nd.mnt->mnt_root) if (old_nd.dentry != old_nd.mnt->mnt_root)
goto out2; goto out1;
if (old_nd.mnt == old_nd.mnt->mnt_parent) if (old_nd.mnt == old_nd.mnt->mnt_parent)
goto out2; goto out1;
if (S_ISDIR(nd->dentry->d_inode->i_mode) != if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
S_ISDIR(old_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; err = -ELOOP;
for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent) for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
if (p == old_nd.mnt) if (p == old_nd.mnt)
goto out2; goto out1;
err = 0;
detach_mnt(old_nd.mnt, &parent_nd); if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd)))
attach_mnt(old_nd.mnt, nd); goto out1;
touch_namespace(current->namespace);
spin_lock(&vfsmount_lock);
/* if the mount is moved, it should no longer be expire /* if the mount is moved, it should no longer be expire
* automatically */ * automatically */
list_del_init(&old_nd.mnt->mnt_expire); list_del_init(&old_nd.mnt->mnt_expire);
out2:
spin_unlock(&vfsmount_lock); spin_unlock(&vfsmount_lock);
out1: out1:
up(&nd->dentry->d_inode->i_sem); up(&nd->dentry->d_inode->i_sem);
...@@ -1467,6 +1492,10 @@ asmlinkage long sys_pivot_root(const char __user * new_root, ...@@ -1467,6 +1492,10 @@ asmlinkage long sys_pivot_root(const char __user * new_root,
down_write(&namespace_sem); down_write(&namespace_sem);
down(&old_nd.dentry->d_inode->i_sem); down(&old_nd.dentry->d_inode->i_sem);
error = -EINVAL; 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)) if (!check_mnt(user_nd.mnt))
goto out2; goto out2;
error = -ENOENT; error = -ENOENT;
......
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