[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: Ram Pai <linuxram@us.ibm.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Ram Pai
Linus Torvalds
Родитель
a58b0eb8e6
Коммит
5afe002213
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@ -227,8 +227,17 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
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mnt->mnt_mountpoint = mnt->mnt_root;
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mnt->mnt_parent = mnt;
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if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
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list_add(&mnt->mnt_share, &old->mnt_share);
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if (flag & CL_SLAVE) {
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list_add(&mnt->mnt_slave, &old->mnt_slave_list);
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mnt->mnt_master = old;
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CLEAR_MNT_SHARED(mnt);
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} else {
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if ((flag & CL_PROPAGATION) || IS_MNT_SHARED(old))
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list_add(&mnt->mnt_share, &old->mnt_share);
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if (IS_MNT_SLAVE(old))
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list_add(&mnt->mnt_slave, &old->mnt_slave);
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mnt->mnt_master = old->mnt_master;
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}
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if (flag & CL_MAKE_SHARED)
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set_mnt_shared(mnt);
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@ -689,18 +698,18 @@ Enomem:
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*
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* NOTE: in the table below explains the semantics when a source mount
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* of a given type is attached to a destination mount of a given type.
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* ---------------------------------------------
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* | BIND MOUNT OPERATION |
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* |********************************************
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* | source-->| shared | private |
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* | dest | | |
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* | | | | |
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* | v | | |
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* |********************************************
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* | shared | shared (++) | shared (+) |
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* | | | |
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* |non-shared| shared (+) | private |
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* *********************************************
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* -------------------------------------------------------------
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* | BIND MOUNT OPERATION |
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* |*************************************************************
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* | source-->| shared | private | slave |
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* | dest | | | |
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* | | | | | |
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* | v | | | |
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* |*************************************************************
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* | shared | shared (++) | shared (+) | shared(+++)|
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* | | | | |
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* |non-shared| shared (+) | private | slave (*) |
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* **************************************************************
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* A bind operation clones the source mount and mounts the clone on the
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* destination mount.
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*
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@ -710,21 +719,33 @@ Enomem:
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* (+) the cloned mount is created under the destination mount and is marked
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* as shared. The cloned mount is added to the peer group of the source
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* mount.
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* ---------------------------------------------
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* | MOVE MOUNT OPERATION |
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* |********************************************
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* | source-->| shared | private |
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* | dest | | |
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* | | | | |
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* | v | | |
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* |********************************************
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* | shared | shared (+) | shared (+) |
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* | | | |
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* |non-shared| shared (+*) | private |
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* *********************************************
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* (+) the mount is moved to the destination. And is then propagated to all
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* the mounts in the propagation tree of the destination mount.
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* (+++) the mount is propagated to all the mounts in the propagation tree
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* of the destination mount and the cloned mount is made slave
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* of the same master as that of the source mount. The cloned mount
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* is marked as 'shared and slave'.
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* (*) the cloned mount is made a slave of the same master as that of the
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* source mount.
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*
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* --------------------------------------------------------------
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* | MOVE MOUNT OPERATION |
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* |*************************************************************
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* | source-->| shared | private | slave |
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* | dest | | | |
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* | | | | | |
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* | v | | | |
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* |*************************************************************
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* | shared | shared (+) | shared (+) | shared(+++) |
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* | | | | |
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* |non-shared| shared (+*) | private | slave (*) |
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* **************************************************************
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*
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* (+) the mount is moved to the destination. And is then propagated to
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* all the mounts in the propagation tree of the destination mount.
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* (+*) the mount is moved to the destination.
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* (+++) the mount is moved to the destination and is then propagated to
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* all the mounts belonging to the destination mount's propagation tree.
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* the mount is marked as 'shared and slave'.
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* (*) the mount continues to be a slave at the new location.
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*
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* if the source mount is a tree, the operations explained above is
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* applied to each mount in the tree.
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81
fs/pnode.c
81
fs/pnode.c
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@ -17,6 +17,16 @@ static inline struct vfsmount *next_peer(struct vfsmount *p)
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return list_entry(p->mnt_share.next, struct vfsmount, mnt_share);
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}
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static inline struct vfsmount *first_slave(struct vfsmount *p)
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{
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return list_entry(p->mnt_slave_list.next, struct vfsmount, mnt_slave);
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}
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static inline struct vfsmount *next_slave(struct vfsmount *p)
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{
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return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);
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}
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static int do_make_slave(struct vfsmount *mnt)
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{
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struct vfsmount *peer_mnt = mnt, *master = mnt->mnt_master;
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@ -83,10 +93,64 @@ void change_mnt_propagation(struct vfsmount *mnt, int type)
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static struct vfsmount *propagation_next(struct vfsmount *m,
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struct vfsmount *origin)
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{
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m = next_peer(m);
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if (m == origin)
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return NULL;
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return m;
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/* are there any slaves of this mount? */
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if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
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return first_slave(m);
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while (1) {
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struct vfsmount *next;
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struct vfsmount *master = m->mnt_master;
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if ( master == origin->mnt_master ) {
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next = next_peer(m);
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return ((next == origin) ? NULL : next);
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} else if (m->mnt_slave.next != &master->mnt_slave_list)
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return next_slave(m);
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/* back at master */
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m = master;
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}
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}
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/*
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* return the source mount to be used for cloning
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*
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* @dest the current destination mount
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* @last_dest the last seen destination mount
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* @last_src the last seen source mount
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* @type return CL_SLAVE if the new mount has to be
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* cloned as a slave.
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*/
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static struct vfsmount *get_source(struct vfsmount *dest,
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struct vfsmount *last_dest,
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struct vfsmount *last_src,
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int *type)
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{
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struct vfsmount *p_last_src = NULL;
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struct vfsmount *p_last_dest = NULL;
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*type = CL_PROPAGATION;;
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if (IS_MNT_SHARED(dest))
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*type |= CL_MAKE_SHARED;
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while (last_dest != dest->mnt_master) {
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p_last_dest = last_dest;
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p_last_src = last_src;
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last_dest = last_dest->mnt_master;
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last_src = last_src->mnt_master;
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}
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if (p_last_dest) {
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do {
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p_last_dest = next_peer(p_last_dest);
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} while (IS_MNT_NEW(p_last_dest));
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}
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if (dest != p_last_dest) {
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*type |= CL_SLAVE;
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return last_src;
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} else
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return p_last_src;
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}
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/*
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@ -114,16 +178,15 @@ int propagate_mnt(struct vfsmount *dest_mnt, struct dentry *dest_dentry,
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for (m = propagation_next(dest_mnt, dest_mnt); m;
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m = propagation_next(m, dest_mnt)) {
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int type = CL_PROPAGATION;
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int type;
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struct vfsmount *source;
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if (IS_MNT_NEW(m))
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continue;
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if (IS_MNT_SHARED(m))
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type |= CL_MAKE_SHARED;
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source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
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if (!(child = copy_tree(source_mnt, source_mnt->mnt_root,
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type))) {
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if (!(child = copy_tree(source, source->mnt_root, type))) {
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ret = -ENOMEM;
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list_splice(tree_list, tmp_list.prev);
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goto out;
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