Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

[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

fs/namespace.c

+46 −17
Original line number Diff line number Diff line
@@ -661,6 +661,9 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 
/*

 *  @source_mnt : mount tree to be 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 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 
 * (+)   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 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 
 * 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);

	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;