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fs/pnode.c
15.1 KB
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// SPDX-License-Identifier: GPL-2.0-only |
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/* * linux/fs/pnode.c * * (C) Copyright IBM Corporation 2005. |
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* Author : Ram Pai (linuxram@us.ibm.com) |
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*/ |
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#include <linux/mnt_namespace.h> |
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#include <linux/mount.h> #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) { return list_entry(p->mnt_slave_list.prev, struct mount, mnt_slave); } |
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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, struct mnt_namespace *ns, const struct path *root) |
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{ |
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struct mount *m = mnt; |
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do { /* 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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|
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m = next_peer(m); |
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} while (m != mnt); |
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return NULL; } /* * Get ID of closest dominating peer group having a representative * under the given root. * * Caller must hold namespace_sem */ |
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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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|
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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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} return 0; } |
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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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|
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if (list_empty(&mnt->mnt_share)) { if (IS_MNT_SHARED(mnt)) { mnt_release_group_id(mnt); CLEAR_MNT_SHARED(mnt); } master = mnt->mnt_master; if (!master) { struct list_head *p = &mnt->mnt_slave_list; while (!list_empty(p)) { slave_mnt = list_first_entry(p, struct mount, mnt_slave); list_del_init(&slave_mnt->mnt_slave); slave_mnt->mnt_master = NULL; } return 0; } |
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} else { |
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struct mount *m; /* * slave 'mnt' to a peer mount that has the * same root dentry. If none is available then * slave it to anything that is available. */ for (m = master = next_peer(mnt); m != mnt; m = next_peer(m)) { if (m->mnt.mnt_root == mnt->mnt.mnt_root) { master = m; break; } |
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} |
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list_del_init(&mnt->mnt_share); mnt->mnt_group_id = 0; CLEAR_MNT_SHARED(mnt); |
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} |
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list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave) slave_mnt->mnt_master = master; list_move(&mnt->mnt_slave, &master->mnt_slave_list); list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev); 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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/* * vfsmount lock must be held for write */ |
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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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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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/* * get the next mount in the propagation tree. * @m: the mount seen last * @origin: the original mount from where the tree walk initiated |
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* * Note that peer groups form contiguous segments of slave lists. * We rely on that in get_source() to be able to find out if * vfsmount found while iterating with propagation_next() is * a peer of one we'd found earlier. |
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*/ |
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static struct mount *propagation_next(struct mount *m, 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); while (1) { |
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struct mount *master = m->mnt_master; |
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|
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if (master == origin->mnt_master) { |
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struct mount *next = next_peer(m); 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); /* back at master */ m = master; } } |
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static struct mount *skip_propagation_subtree(struct mount *m, struct mount *origin) { /* * Advance m such that propagation_next will not return * the slaves of m. */ if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list)) m = last_slave(m); return m; } |
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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) { while (1) { struct mount *next; if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list)) return first_slave(m); next = next_peer(m); if (m->mnt_group_id == origin->mnt_group_id) { if (next == origin) return NULL; } else if (m->mnt_slave.next != &next->mnt_slave) break; m = next; } /* m is the last peer */ while (1) { struct mount *master = m->mnt_master; if (m->mnt_slave.next != &master->mnt_slave_list) return next_slave(m); m = next_peer(master); if (master->mnt_group_id == origin->mnt_group_id) break; if (master->mnt_slave.next == &m->mnt_slave) break; m = master; } if (m == origin) 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; static struct hlist_head *list; |
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static inline bool peers(struct mount *m1, struct mount *m2) { return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id; } |
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static int propagate_one(struct mount *m) { struct mount *child; int type; /* skip ones added by this propagate_mnt() */ if (IS_MNT_NEW(m)) return 0; /* skip if mountpoint isn't covered by it */ if (!is_subdir(mp->m_dentry, m->mnt.mnt_root)) return 0; |
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if (peers(m, last_dest)) { |
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type = CL_MAKE_SHARED; } else { struct mount *n, *p; |
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bool done; |
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for (n = m; ; n = p) { 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 { struct mount *parent = last_source->mnt_parent; if (last_source == first_source) break; done = parent->mnt_master == p; if (done && peers(n, parent)) break; last_source = last_source->mnt_master; } while (!done); |
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type = CL_SLAVE; /* beginning of peer group among the slaves? */ if (IS_MNT_SHARED(m)) type |= CL_MAKE_SHARED; |
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} |
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|
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child = copy_tree(last_source, last_source->mnt.mnt_root, type); if (IS_ERR(child)) return PTR_ERR(child); mnt_set_mountpoint(m, mp, child); last_dest = m; last_source = child; if (m->mnt_master != dest_master) { read_seqlock_excl(&mount_lock); SET_MNT_MARK(m->mnt_master); read_sequnlock_excl(&mount_lock); } hlist_add_head(&child->mnt_hash, list); |
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return count_mounts(m->mnt_ns, child); |
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} /* * mount 'source_mnt' under the destination 'dest_mnt' at * dentry 'dest_dentry'. And propagate that mount to * all the peer and slave mounts of 'dest_mnt'. * Link all the new mounts into a propagation tree headed at * source_mnt. Also link all the new mounts using ->mnt_list * headed at source_mnt's ->mnt_list * * @dest_mnt: destination mount. * @dest_dentry: destination dentry. * @source_mnt: source mount. * @tree_list : list of heads of trees to be attached. */ |
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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 * propagate_one(); everything is serialized by namespace_sem, * so globals will do just fine. */ |
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last_dest = dest_mnt; |
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first_source = source_mnt; |
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last_source = source_mnt; mp = dest_mp; list = tree_list; dest_master = dest_mnt->mnt_master; /* all peers of dest_mnt, except dest_mnt itself */ for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) { ret = propagate_one(n); if (ret) |
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goto out; |
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} |
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|
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/* all slave groups */ for (m = next_group(dest_mnt, dest_mnt); m; m = next_group(m, dest_mnt)) { /* everything in that slave group */ n = m; do { ret = propagate_one(n); if (ret) goto out; n = next_peer(n); } while (n != m); |
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} out: |
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read_seqlock_excl(&mount_lock); hlist_for_each_entry(n, tree_list, mnt_hash) { m = n->mnt_parent; if (m->mnt_master != dest_mnt->mnt_master) 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) { /* If there is exactly one mount covering mnt completely return it. */ struct mount *child; if (!list_is_singular(&mnt->mnt_mounts)) return NULL; child = list_first_entry(&mnt->mnt_mounts, struct mount, mnt_child); if (child->mnt_mountpoint != mnt->mnt.mnt_root) return NULL; return child; } |
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/* * return true if the refcount is greater than count */ |
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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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} /* * check if the mount 'mnt' can be unmounted successfully. * @mnt: the mount to be checked for unmount * NOTE: unmounting 'mnt' would naturally propagate to all * other mounts its parent propagates to. * Check if any of these mounts that **do not have submounts** * 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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|
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if (mnt == parent) |
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return do_refcount_check(mnt, refcnt); /* * quickly check if the current mount can be unmounted. * If not, we don't have to go checking for all other * mounts */ |
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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; m = propagation_next(m, parent)) { |
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int count = 1; child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); if (!child) continue; /* Is there exactly one mount on the child that covers * it completely whose reference should be ignored? */ topper = find_topper(child); if (topper) count += 1; else if (!list_empty(&child->mnt_mounts)) continue; if (do_refcount_check(child, count)) return 1; |
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} |
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return 0; |
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} /* |
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* Clear MNT_LOCKED when it can be shown to be safe. * * mount_lock lock must be held for write */ void propagate_mount_unlock(struct mount *mnt) { struct mount *parent = mnt->mnt_parent; struct mount *m, *child; BUG_ON(parent == mnt); for (m = propagation_next(parent, parent); m; m = propagation_next(m, parent)) { |
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child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); |
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if (child) child->mnt.mnt_flags &= ~MNT_LOCKED; } } |
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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); mnt->mnt.mnt_flags |= MNT_UMOUNT; list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_umounting); list_move_tail(&mnt->mnt_list, to_umount); |
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} /* |
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* NOTE: unmounting 'mnt' naturally propagates to all other mounts its * parent propagates to. */ |
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static bool __propagate_umount(struct mount *mnt, struct list_head *to_umount, struct list_head *to_restore) |
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{ |
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bool progress = false; struct mount *child; |
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|
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/* * The state of the parent won't change if this mount is * already unmounted or marked as without children. */ if (mnt->mnt.mnt_flags & (MNT_UMOUNT | MNT_MARKED)) goto out; |
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|
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/* Verify topper is the only grandchild that has not been * speculatively unmounted. */ list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { 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)) continue; /* Found a mounted child */ goto children; } |
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|
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/* Mark mounts that can be unmounted if not locked */ SET_MNT_MARK(mnt); progress = true; |
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|
99b19d164 mnt: In propgate_... |
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/* If a mount is without children and not locked umount it. */ if (!IS_MNT_LOCKED(mnt)) { umount_one(mnt, to_umount); } else { children: list_move_tail(&mnt->mnt_umounting, to_restore); } out: return progress; } static void umount_list(struct list_head *to_umount, struct list_head *to_restore) { struct mount *mnt, *child, *tmp; list_for_each_entry(mnt, to_umount, mnt_list) { list_for_each_entry_safe(child, tmp, &mnt->mnt_mounts, mnt_child) { /* topper? */ if (child->mnt_mountpoint == mnt->mnt.mnt_root) list_move_tail(&child->mnt_umounting, to_restore); else umount_one(child, to_umount); |
38129a13e switch mnt_hash t... |
478 |
} |
a05964f39 [PATCH] shared mo... |
479 480 |
} } |
99b19d164 mnt: In propgate_... |
481 |
static void restore_mounts(struct list_head *to_restore) |
570487d3f mnt: In umount pr... |
482 |
{ |
99b19d164 mnt: In propgate_... |
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/* Restore mounts to a clean working state */ while (!list_empty(to_restore)) { |
570487d3f mnt: In umount pr... |
485 486 |
struct mount *mnt, *parent; struct mountpoint *mp; |
99b19d164 mnt: In propgate_... |
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mnt = list_first_entry(to_restore, struct mount, mnt_umounting); CLEAR_MNT_MARK(mnt); list_del_init(&mnt->mnt_umounting); |
570487d3f mnt: In umount pr... |
490 |
|
99b19d164 mnt: In propgate_... |
491 |
/* Should this mount be reparented? */ |
570487d3f mnt: In umount pr... |
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mp = mnt->mnt_mp; parent = mnt->mnt_parent; while (parent->mnt.mnt_flags & MNT_UMOUNT) { mp = parent->mnt_mp; parent = parent->mnt_parent; } |
99b19d164 mnt: In propgate_... |
498 499 |
if (parent != mnt->mnt_parent) mnt_change_mountpoint(parent, mp, mnt); |
570487d3f mnt: In umount pr... |
500 501 |
} } |
296990deb mnt: Make propaga... |
502 503 504 505 506 507 508 509 |
static void cleanup_umount_visitations(struct list_head *visited) { while (!list_empty(visited)) { struct mount *mnt = list_first_entry(visited, struct mount, mnt_umounting); list_del_init(&mnt->mnt_umounting); } } |
a05964f39 [PATCH] shared mo... |
510 511 512 513 |
/* * collect all mounts that receive propagation from the mount in @list, * and return these additional mounts in the same list. * @list: the list of mounts to be unmounted. |
99b7db7b8 fs: brlock vfsmou... |
514 515 |
* * vfsmount lock must be held for write |
a05964f39 [PATCH] shared mo... |
516 |
*/ |
c003b26ff mnt: In umount_tr... |
517 |
int propagate_umount(struct list_head *list) |
a05964f39 [PATCH] shared mo... |
518 |
{ |
61ef47b1e vfs: spread struc... |
519 |
struct mount *mnt; |
99b19d164 mnt: In propgate_... |
520 521 |
LIST_HEAD(to_restore); LIST_HEAD(to_umount); |
296990deb mnt: Make propaga... |
522 |
LIST_HEAD(visited); |
a05964f39 [PATCH] shared mo... |
523 |
|
296990deb mnt: Make propaga... |
524 525 |
/* Find candidates for unmounting */ list_for_each_entry_reverse(mnt, list, mnt_list) { |
99b19d164 mnt: In propgate_... |
526 527 |
struct mount *parent = mnt->mnt_parent; struct mount *m; |
0c56fe314 mnt: Don't propag... |
528 |
|
296990deb mnt: Make propaga... |
529 530 531 532 533 534 535 536 537 538 |
/* * If this mount has already been visited it is known that it's * entire peer group and all of their slaves in the propagation * tree for the mountpoint has already been visited and there is * no need to visit them again. */ if (!list_empty(&mnt->mnt_umounting)) continue; list_add_tail(&mnt->mnt_umounting, &visited); |
99b19d164 mnt: In propgate_... |
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for (m = propagation_next(parent, parent); m; m = propagation_next(m, parent)) { struct mount *child = __lookup_mnt(&m->mnt, mnt->mnt_mountpoint); if (!child) continue; |
296990deb mnt: Make propaga... |
545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 |
if (!list_empty(&child->mnt_umounting)) { /* * If the child has already been visited it is * know that it's entire peer group and all of * their slaves in the propgation tree for the * mountpoint has already been visited and there * is no need to visit this subtree again. */ m = skip_propagation_subtree(m, parent); continue; } else if (child->mnt.mnt_flags & MNT_UMOUNT) { /* * We have come accross an partially unmounted * 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; } |
99b19d164 mnt: In propgate_... |
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/* 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; } } } |
570487d3f mnt: In umount pr... |
575 |
|
99b19d164 mnt: In propgate_... |
576 577 |
umount_list(&to_umount, &to_restore); restore_mounts(&to_restore); |
296990deb mnt: Make propaga... |
578 |
cleanup_umount_visitations(&visited); |
99b19d164 mnt: In propgate_... |
579 |
list_splice_tail(&to_umount, list); |
570487d3f mnt: In umount pr... |
580 |
|
a05964f39 [PATCH] shared mo... |
581 582 |
return 0; } |