Commit 5afe0022 authored by Ram Pai's avatar Ram Pai Committed by Linus Torvalds
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[PATCH] handling of slave mounts 



This makes bind, rbind, move, clone namespace and umount operations
aware of the semantics of slave mount (see Documentation/sharedsubtree.txt
in the last patch of the 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 a58b0eb8

fs/namespace.c

+49 −28
Original line number Diff line number Diff line
@@ -227,8 +227,17 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, 
		mnt->mnt_mountpoint = mnt->mnt_root;

		mnt->mnt_parent = mnt;



		if (flag & CL_SLAVE) {

			list_add(&mnt->mnt_slave, &old->mnt_slave_list);

			mnt->mnt_master = old;

			CLEAR_MNT_SHARED(mnt);

		} else {

			if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))

				list_add(&mnt->mnt_share, &old->mnt_share);

			if (IS_MNT_SLAVE(old))

				list_add(&mnt->mnt_slave, &old->mnt_slave);

			mnt->mnt_master = old->mnt_master;

		}

		if (flag & CL_MAKE_SHARED)

			set_mnt_shared(mnt);
@@ -689,18 +698,18 @@ struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, 
 *

 *  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.

 * 	---------------------------------------------

 * 	-------------------------------------------------------------

 * 	|         BIND MOUNT OPERATION                               |

 * 	|********************************************

 * 	| source-->| shared        |       private  |

 * 	| dest     |               |                |

 * 	|*************************************************************

 * 	| source-->| shared        |       private  |       slave    |

 * 	| dest     |               |                |                |

 * 	|   |      |               |                |                |

 * 	|   v      |               |                |                |

 * 	|*************************************************************

 * 	|  shared  | shared (++)   |     shared (+) |     shared(+++)|

 * 	|          |               |                |                |

 * 	|   v      |               |                |

 * 	|********************************************

 * 	|  shared  | shared (++)   |     shared (+) |

 * 	|          |               |                |

 * 	|non-shared| shared (+)    |      private   |

 * 	*********************************************

 * 	|non-shared| shared (+)    |      private   |      slave (*) |

 * 	**************************************************************

 * A bind operation clones the source mount and mounts the clone on the

 * destination mount.

 *
@@ -710,21 +719,33 @@ 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.

 * 	---------------------------------------------

 * (+++) the mount is propagated to all the mounts in the propagation tree

 *       of the destination mount and the cloned mount is made slave

 *       of the same master as that of the source mount. The cloned mount

 *       is marked as 'shared and slave'.

 * (*)   the cloned mount is made a slave of the same master as that of the

 * 	 source mount.

 *

 * 	--------------------------------------------------------------

 * 	|         		MOVE MOUNT OPERATION                 |

 * 	|********************************************

 * 	| source-->| shared        |       private  |

 * 	| dest     |               |                |

 * 	|*************************************************************

 * 	| source-->| shared        |       private  |       slave    |

 * 	| dest     |               |                |                |

 * 	|   |      |               |                |                |

 * 	|   v      |               |                |                |

 * 	|*************************************************************

 * 	|  shared  | shared (+)    |     shared (+) |    shared(+++) |

 * 	|          |               |                |                |

 * 	|   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.

 * 	|non-shared| shared (+*)   |      private   |    slave (*)   |

 * 	**************************************************************

 *

 * (+)  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.

 * (+++)  the mount is moved to the destination and is then propagated to

 * 	all the mounts belonging to the destination mount's propagation tree.

 * 	the mount is marked as 'shared and slave'.

 * (*)	the mount continues to be a slave at the new location.

 *

 * if the source mount is a tree, the operations explained above is

 * applied to each mount in the tree.

fs/pnode.c

+72 −9
Original line number Diff line number Diff line
@@ -17,6 +17,16 @@ static inline struct vfsmount *next_peer(struct vfsmount *p) 
	return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);

}



static inline struct vfsmount *first_slave(struct vfsmount *p)

{

	return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);

}



static inline struct vfsmount *next_slave(struct vfsmount *p)

{

	return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);

}



static int do_make_slave(struct vfsmount *mnt)

{

	struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
@@ -83,10 +93,64 @@ void change_mnt_propagation(struct vfsmount *mnt, int type) 
static struct vfsmount *propagation_next(struct vfsmount *m,

					 struct vfsmount *origin)

{

	m = next_peer(m);

	if (m == origin)

		return NULL;

	return m;

	/* are there any slaves of this mount? */

	if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))

		return first_slave(m);



	while (1) {

		struct vfsmount *next;

		struct vfsmount *master = m->mnt_master;



		if ( master == origin->mnt_master ) {

			next = next_peer(m);

			return ((next == origin) ? NULL : next);

		} else if (m->mnt_slave.next != &master->mnt_slave_list)

			return next_slave(m);



		/* back at master */

		m = master;

	}

}



/*

 * return the source mount to be used for cloning

 *

 * @dest 	the current destination mount

 * @last_dest  	the last seen destination mount

 * @last_src  	the last seen source mount

 * @type	return CL_SLAVE if the new mount has to be

 * 		cloned as a slave.

 */

static struct vfsmount *get_source(struct vfsmount *dest,

					struct vfsmount *last_dest,

					struct vfsmount *last_src,

					int *type)

{

	struct vfsmount *p_last_src = NULL;

	struct vfsmount *p_last_dest = NULL;

	*type = CL_PROPAGATION;;



	if (IS_MNT_SHARED(dest))

		*type |= CL_MAKE_SHARED;



	while (last_dest != dest->mnt_master) {

		p_last_dest = last_dest;

		p_last_src = last_src;

		last_dest = last_dest->mnt_master;

		last_src = last_src->mnt_master;

	}



	if (p_last_dest) {

		do {

			p_last_dest = next_peer(p_last_dest);

		} while (IS_MNT_NEW(p_last_dest));

	}



	if (dest != p_last_dest) {

		*type |= CL_SLAVE;

		return last_src;

	} else

		return p_last_src;

}



/*
@@ -114,16 +178,15 @@ int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry, 


	for (m = propagation_next(dest_mnt, dest_mnt); m;

			m = propagation_next(m, dest_mnt)) {

		int type = CL_PROPAGATION;

		int type;

		struct vfsmount *source;



		if (IS_MNT_NEW(m))

			continue;



		if (IS_MNT_SHARED(m))

			type |= CL_MAKE_SHARED;

		source =  get_source(m, prev_dest_mnt, prev_src_mnt, &type);



		if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,

						type))) {

		if (!(child = copy_tree(source, source->mnt_root, type))) {

			ret = -ENOMEM;

			list_splice(tree_list, tmp_list.prev);

			goto out;