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602 lines
15 KiB
602 lines
15 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* linux/fs/pnode.c |
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* |
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* (C) Copyright IBM Corporation 2005. |
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* Author : Ram Pai ([email protected]) |
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*/ |
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#include <linux/mnt_namespace.h> |
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#include <linux/mount.h> |
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#include <linux/fs.h> |
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#include <linux/nsproxy.h> |
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#include <uapi/linux/mount.h> |
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#include "internal.h" |
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#include "pnode.h" |
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/* return the next shared peer mount of @p */ |
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static inline struct mount *next_peer(struct mount *p) |
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{ |
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return list_entry(p->mnt_share.next, struct mount, mnt_share); |
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} |
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static inline struct mount *first_slave(struct mount *p) |
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{ |
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return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave); |
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} |
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static inline struct mount *last_slave(struct mount *p) |
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{ |
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return list_entry(p->mnt_slave_list.prev, struct mount, mnt_slave); |
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} |
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static inline struct mount *next_slave(struct mount *p) |
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{ |
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return list_entry(p->mnt_slave.next, struct mount, mnt_slave); |
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} |
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static struct mount *get_peer_under_root(struct mount *mnt, |
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struct mnt_namespace *ns, |
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const struct path *root) |
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{ |
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struct mount *m = mnt; |
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do { |
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/* Check the namespace first for optimization */ |
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if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root)) |
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return m; |
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m = next_peer(m); |
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} while (m != mnt); |
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return NULL; |
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} |
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/* |
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* Get ID of closest dominating peer group having a representative |
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* under the given root. |
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* |
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* Caller must hold namespace_sem |
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*/ |
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int get_dominating_id(struct mount *mnt, const struct path *root) |
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{ |
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struct mount *m; |
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for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) { |
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struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root); |
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if (d) |
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return d->mnt_group_id; |
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} |
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return 0; |
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} |
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static int do_make_slave(struct mount *mnt) |
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{ |
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struct mount *master, *slave_mnt; |
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if (list_empty(&mnt->mnt_share)) { |
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if (IS_MNT_SHARED(mnt)) { |
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mnt_release_group_id(mnt); |
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CLEAR_MNT_SHARED(mnt); |
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} |
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master = mnt->mnt_master; |
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if (!master) { |
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struct list_head *p = &mnt->mnt_slave_list; |
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while (!list_empty(p)) { |
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slave_mnt = list_first_entry(p, |
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struct mount, mnt_slave); |
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list_del_init(&slave_mnt->mnt_slave); |
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slave_mnt->mnt_master = NULL; |
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} |
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return 0; |
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} |
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} else { |
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struct mount *m; |
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/* |
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* slave 'mnt' to a peer mount that has the |
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* same root dentry. If none is available then |
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* slave it to anything that is available. |
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*/ |
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for (m = master = next_peer(mnt); m != mnt; m = next_peer(m)) { |
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if (m->mnt.mnt_root == mnt->mnt.mnt_root) { |
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master = m; |
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break; |
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} |
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} |
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list_del_init(&mnt->mnt_share); |
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mnt->mnt_group_id = 0; |
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CLEAR_MNT_SHARED(mnt); |
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} |
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list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave) |
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slave_mnt->mnt_master = master; |
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list_move(&mnt->mnt_slave, &master->mnt_slave_list); |
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list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev); |
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INIT_LIST_HEAD(&mnt->mnt_slave_list); |
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mnt->mnt_master = master; |
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return 0; |
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} |
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/* |
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* vfsmount lock must be held for write |
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*/ |
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void change_mnt_propagation(struct mount *mnt, int type) |
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{ |
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if (type == MS_SHARED) { |
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set_mnt_shared(mnt); |
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return; |
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} |
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do_make_slave(mnt); |
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if (type != MS_SLAVE) { |
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list_del_init(&mnt->mnt_slave); |
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mnt->mnt_master = NULL; |
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if (type == MS_UNBINDABLE) |
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mnt->mnt.mnt_flags |= MNT_UNBINDABLE; |
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else |
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mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE; |
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} |
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} |
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/* |
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* get the next mount in the propagation tree. |
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* @m: the mount seen last |
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* @origin: the original mount from where the tree walk initiated |
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* |
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* Note that peer groups form contiguous segments of slave lists. |
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* We rely on that in get_source() to be able to find out if |
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* vfsmount found while iterating with propagation_next() is |
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* a peer of one we'd found earlier. |
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*/ |
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static struct mount *propagation_next(struct mount *m, |
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struct mount *origin) |
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{ |
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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 mount *master = m->mnt_master; |
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if (master == origin->mnt_master) { |
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struct mount *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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static struct mount *skip_propagation_subtree(struct mount *m, |
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struct mount *origin) |
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{ |
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/* |
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* Advance m such that propagation_next will not return |
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* the slaves of m. |
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*/ |
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if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list)) |
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m = last_slave(m); |
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return m; |
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} |
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static struct mount *next_group(struct mount *m, struct mount *origin) |
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{ |
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while (1) { |
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while (1) { |
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struct mount *next; |
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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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next = next_peer(m); |
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if (m->mnt_group_id == origin->mnt_group_id) { |
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if (next == origin) |
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return NULL; |
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} else if (m->mnt_slave.next != &next->mnt_slave) |
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break; |
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m = next; |
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} |
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/* m is the last peer */ |
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while (1) { |
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struct mount *master = m->mnt_master; |
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if (m->mnt_slave.next != &master->mnt_slave_list) |
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return next_slave(m); |
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m = next_peer(master); |
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if (master->mnt_group_id == origin->mnt_group_id) |
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break; |
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if (master->mnt_slave.next == &m->mnt_slave) |
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break; |
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m = master; |
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} |
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if (m == origin) |
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return NULL; |
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} |
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} |
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/* all accesses are serialized by namespace_sem */ |
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static struct mount *last_dest, *first_source, *last_source, *dest_master; |
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static struct mountpoint *mp; |
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static struct hlist_head *list; |
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static inline bool peers(struct mount *m1, struct mount *m2) |
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{ |
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return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id; |
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} |
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static int propagate_one(struct mount *m) |
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{ |
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struct mount *child; |
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int type; |
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/* skip ones added by this propagate_mnt() */ |
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if (IS_MNT_NEW(m)) |
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return 0; |
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/* skip if mountpoint isn't covered by it */ |
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if (!is_subdir(mp->m_dentry, m->mnt.mnt_root)) |
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return 0; |
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if (peers(m, last_dest)) { |
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type = CL_MAKE_SHARED; |
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} else { |
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struct mount *n, *p; |
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bool done; |
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for (n = m; ; n = p) { |
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p = n->mnt_master; |
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if (p == dest_master || IS_MNT_MARKED(p)) |
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break; |
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} |
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do { |
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struct mount *parent = last_source->mnt_parent; |
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if (last_source == first_source) |
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break; |
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done = parent->mnt_master == p; |
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if (done && peers(n, parent)) |
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break; |
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last_source = last_source->mnt_master; |
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} while (!done); |
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type = CL_SLAVE; |
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/* beginning of peer group among the slaves? */ |
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if (IS_MNT_SHARED(m)) |
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type |= CL_MAKE_SHARED; |
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} |
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child = copy_tree(last_source, last_source->mnt.mnt_root, type); |
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if (IS_ERR(child)) |
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return PTR_ERR(child); |
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read_seqlock_excl(&mount_lock); |
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mnt_set_mountpoint(m, mp, child); |
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if (m->mnt_master != dest_master) |
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SET_MNT_MARK(m->mnt_master); |
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read_sequnlock_excl(&mount_lock); |
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last_dest = m; |
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last_source = child; |
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hlist_add_head(&child->mnt_hash, list); |
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return count_mounts(m->mnt_ns, child); |
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} |
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/* |
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* mount 'source_mnt' under the destination 'dest_mnt' at |
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* dentry 'dest_dentry'. And propagate that mount to |
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* all the peer and slave mounts of 'dest_mnt'. |
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* Link all the new mounts into a propagation tree headed at |
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* source_mnt. Also link all the new mounts using ->mnt_list |
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* headed at source_mnt's ->mnt_list |
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* |
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* @dest_mnt: destination mount. |
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* @dest_dentry: destination dentry. |
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* @source_mnt: source mount. |
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* @tree_list : list of heads of trees to be attached. |
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*/ |
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int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp, |
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struct mount *source_mnt, struct hlist_head *tree_list) |
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{ |
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struct mount *m, *n; |
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int ret = 0; |
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/* |
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* we don't want to bother passing tons of arguments to |
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* propagate_one(); everything is serialized by namespace_sem, |
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* so globals will do just fine. |
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*/ |
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last_dest = dest_mnt; |
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first_source = source_mnt; |
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last_source = source_mnt; |
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mp = dest_mp; |
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list = tree_list; |
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dest_master = dest_mnt->mnt_master; |
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/* all peers of dest_mnt, except dest_mnt itself */ |
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for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) { |
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ret = propagate_one(n); |
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if (ret) |
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goto out; |
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} |
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/* all slave groups */ |
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for (m = next_group(dest_mnt, dest_mnt); m; |
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m = next_group(m, dest_mnt)) { |
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/* everything in that slave group */ |
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n = m; |
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do { |
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ret = propagate_one(n); |
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if (ret) |
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goto out; |
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n = next_peer(n); |
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} while (n != m); |
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} |
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out: |
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read_seqlock_excl(&mount_lock); |
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hlist_for_each_entry(n, tree_list, mnt_hash) { |
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m = n->mnt_parent; |
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if (m->mnt_master != dest_mnt->mnt_master) |
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CLEAR_MNT_MARK(m->mnt_master); |
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} |
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read_sequnlock_excl(&mount_lock); |
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return ret; |
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} |
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static struct mount *find_topper(struct mount *mnt) |
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{ |
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/* If there is exactly one mount covering mnt completely return it. */ |
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struct mount *child; |
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if (!list_is_singular(&mnt->mnt_mounts)) |
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return NULL; |
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child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child); |
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if (child->mnt_mountpoint != mnt->mnt.mnt_root) |
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return NULL; |
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return child; |
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} |
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/* |
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* return true if the refcount is greater than count |
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*/ |
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static inline int do_refcount_check(struct mount *mnt, int count) |
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{ |
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return mnt_get_count(mnt) > count; |
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} |
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/* |
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* check if the mount 'mnt' can be unmounted successfully. |
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* @mnt: the mount to be checked for unmount |
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* NOTE: unmounting 'mnt' would naturally propagate to all |
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* other mounts its parent propagates to. |
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* Check if any of these mounts that **do not have submounts** |
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* have more references than 'refcnt'. If so return busy. |
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* |
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* vfsmount lock must be held for write |
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*/ |
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int propagate_mount_busy(struct mount *mnt, int refcnt) |
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{ |
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struct mount *m, *child, *topper; |
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struct mount *parent = mnt->mnt_parent; |
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if (mnt == parent) |
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return do_refcount_check(mnt, refcnt); |
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/* |
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* quickly check if the current mount can be unmounted. |
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* If not, we don't have to go checking for all other |
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* mounts |
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*/ |
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if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt)) |
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return 1; |
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for (m = propagation_next(parent, parent); m; |
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m = propagation_next(m, parent)) { |
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int count = 1; |
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child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); |
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if (!child) |
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continue; |
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/* Is there exactly one mount on the child that covers |
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* it completely whose reference should be ignored? |
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*/ |
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topper = find_topper(child); |
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if (topper) |
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count += 1; |
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else if (!list_empty(&child->mnt_mounts)) |
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continue; |
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if (do_refcount_check(child, count)) |
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return 1; |
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} |
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return 0; |
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} |
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/* |
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* Clear MNT_LOCKED when it can be shown to be safe. |
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* |
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* mount_lock lock must be held for write |
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*/ |
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void propagate_mount_unlock(struct mount *mnt) |
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{ |
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struct mount *parent = mnt->mnt_parent; |
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struct mount *m, *child; |
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BUG_ON(parent == mnt); |
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for (m = propagation_next(parent, parent); m; |
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m = propagation_next(m, parent)) { |
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child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); |
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if (child) |
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child->mnt.mnt_flags &= ~MNT_LOCKED; |
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} |
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} |
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static void umount_one(struct mount *mnt, struct list_head *to_umount) |
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{ |
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CLEAR_MNT_MARK(mnt); |
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mnt->mnt.mnt_flags |= MNT_UMOUNT; |
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list_del_init(&mnt->mnt_child); |
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list_del_init(&mnt->mnt_umounting); |
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list_move_tail(&mnt->mnt_list, to_umount); |
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} |
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/* |
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* NOTE: unmounting 'mnt' naturally propagates to all other mounts its |
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* parent propagates to. |
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*/ |
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static bool __propagate_umount(struct mount *mnt, |
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struct list_head *to_umount, |
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struct list_head *to_restore) |
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{ |
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bool progress = false; |
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struct mount *child; |
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/* |
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* The state of the parent won't change if this mount is |
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* already unmounted or marked as without children. |
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*/ |
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if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED)) |
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goto out; |
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/* Verify topper is the only grandchild that has not been |
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* speculatively unmounted. |
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*/ |
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list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { |
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if (child->mnt_mountpoint == mnt->mnt.mnt_root) |
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continue; |
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if (!list_empty(&child->mnt_umounting) && IS_MNT_MARKED(child)) |
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continue; |
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/* Found a mounted child */ |
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goto children; |
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} |
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/* Mark mounts that can be unmounted if not locked */ |
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SET_MNT_MARK(mnt); |
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progress = true; |
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/* If a mount is without children and not locked umount it. */ |
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if (!IS_MNT_LOCKED(mnt)) { |
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umount_one(mnt, to_umount); |
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} else { |
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children: |
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list_move_tail(&mnt->mnt_umounting, to_restore); |
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} |
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out: |
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return progress; |
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} |
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static void umount_list(struct list_head *to_umount, |
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struct list_head *to_restore) |
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{ |
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struct mount *mnt, *child, *tmp; |
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list_for_each_entry(mnt, to_umount, mnt_list) { |
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list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) { |
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/* topper? */ |
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if (child->mnt_mountpoint == mnt->mnt.mnt_root) |
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list_move_tail(&child->mnt_umounting, to_restore); |
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else |
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umount_one(child, to_umount); |
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} |
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} |
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} |
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static void restore_mounts(struct list_head *to_restore) |
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{ |
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/* Restore mounts to a clean working state */ |
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while (!list_empty(to_restore)) { |
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struct mount *mnt, *parent; |
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struct mountpoint *mp; |
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mnt = list_first_entry(to_restore, struct mount, mnt_umounting); |
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CLEAR_MNT_MARK(mnt); |
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list_del_init(&mnt->mnt_umounting); |
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|
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/* Should this mount be reparented? */ |
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mp = mnt->mnt_mp; |
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parent = mnt->mnt_parent; |
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while (parent->mnt.mnt_flags & MNT_UMOUNT) { |
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mp = parent->mnt_mp; |
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parent = parent->mnt_parent; |
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} |
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if (parent != mnt->mnt_parent) |
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mnt_change_mountpoint(parent, mp, mnt); |
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} |
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} |
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|
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static void cleanup_umount_visitations(struct list_head *visited) |
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{ |
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while (!list_empty(visited)) { |
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struct mount *mnt = |
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list_first_entry(visited, struct mount, mnt_umounting); |
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list_del_init(&mnt->mnt_umounting); |
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} |
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} |
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|
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/* |
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* collect all mounts that receive propagation from the mount in @list, |
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* and return these additional mounts in the same list. |
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* @list: the list of mounts to be unmounted. |
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* |
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* vfsmount lock must be held for write |
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*/ |
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int propagate_umount(struct list_head *list) |
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{ |
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struct mount *mnt; |
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LIST_HEAD(to_restore); |
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LIST_HEAD(to_umount); |
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LIST_HEAD(visited); |
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|
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/* Find candidates for unmounting */ |
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list_for_each_entry_reverse(mnt, list, mnt_list) { |
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struct mount *parent = mnt->mnt_parent; |
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struct mount *m; |
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|
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/* |
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* If this mount has already been visited it is known that it's |
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* entire peer group and all of their slaves in the propagation |
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* tree for the mountpoint has already been visited and there is |
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* no need to visit them again. |
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*/ |
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if (!list_empty(&mnt->mnt_umounting)) |
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continue; |
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|
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list_add_tail(&mnt->mnt_umounting, &visited); |
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for (m = propagation_next(parent, parent); m; |
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m = propagation_next(m, parent)) { |
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struct mount *child = __lookup_mnt(&m->mnt, |
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mnt->mnt_mountpoint); |
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if (!child) |
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continue; |
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|
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if (!list_empty(&child->mnt_umounting)) { |
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/* |
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* If the child has already been visited it is |
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* know that it's entire peer group and all of |
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* their slaves in the propgation tree for the |
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* mountpoint has already been visited and there |
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* is no need to visit this subtree again. |
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*/ |
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m = skip_propagation_subtree(m, parent); |
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continue; |
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} else if (child->mnt.mnt_flags & MNT_UMOUNT) { |
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/* |
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* We have come accross an partially unmounted |
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* mount in list that has not been visited yet. |
|
* Remember it has been visited and continue |
|
* about our merry way. |
|
*/ |
|
list_add_tail(&child->mnt_umounting, &visited); |
|
continue; |
|
} |
|
|
|
/* Check the child and parents while progress is made */ |
|
while (__propagate_umount(child, |
|
&to_umount, &to_restore)) { |
|
/* Is the parent a umount candidate? */ |
|
child = child->mnt_parent; |
|
if (list_empty(&child->mnt_umounting)) |
|
break; |
|
} |
|
} |
|
} |
|
|
|
umount_list(&to_umount, &to_restore); |
|
restore_mounts(&to_restore); |
|
cleanup_umount_visitations(&visited); |
|
list_splice_tail(&to_umount, list); |
|
|
|
return 0; |
|
}
|
|
|