From 88b368f27a094277143d8ecd5a056116f6a41520 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 18 Aug 2014 15:09:26 -0400 Subject: get rid of propagate_umount() mistakenly treating slaves as busy. The check in __propagate_umount() ("has somebody explicitly mounted something on that slave?") is done *before* taking the already doomed victims out of the child lists. Cc: stable@vger.kernel.org Signed-off-by: Al Viro --- fs/namespace.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index a01c7730e9af..3273177873f0 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1253,6 +1253,9 @@ void umount_tree(struct mount *mnt, int how) hlist_add_head(&p->mnt_hash, &tmp_list); } + hlist_for_each_entry(p, &tmp_list, mnt_hash) + list_del_init(&p->mnt_child); + if (how) propagate_umount(&tmp_list); @@ -1263,7 +1266,6 @@ void umount_tree(struct mount *mnt, int how) p->mnt_ns = NULL; if (how < 2) p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; - list_del_init(&p->mnt_child); if (mnt_has_parent(p)) { put_mountpoint(p->mnt_mp); /* move the reference to mountpoint into ->mnt_ex_mountpoint */ -- cgit v1.2.3 From 81b6b06197606b4bef4e427a197aeb808e8d89e1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 30 Aug 2014 18:32:05 -0400 Subject: fix EBUSY on umount() from MNT_SHRINKABLE We need the parents of victims alive until namespace_unlock() gets to dput() of the (ex-)mountpoints. However, that screws up the "is it busy" checks in case when we have shrinkable mounts that need to be killed. Solution: go ahead and decrement refcounts of parents right in umount_tree(), increment them again just before dropping rwsem in namespace_unlock() (and let the loop in the end of namespace_unlock() finally drop those references for good, as we do now). Parents can't get freed until we drop rwsem - at least one reference is kept until then, both in case when parent is among the victims and when it is not. So they'll still be around when we get to namespace_unlock(). Cc: stable@vger.kernel.org # 3.12+ Signed-off-by: Al Viro --- fs/namespace.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'fs/namespace.c') diff --git a/fs/namespace.c b/fs/namespace.c index 3273177873f0..ef42d9bee212 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1217,6 +1217,11 @@ static void namespace_unlock(void) head.first->pprev = &head.first; INIT_HLIST_HEAD(&unmounted); + /* undo decrements we'd done in umount_tree() */ + hlist_for_each_entry(mnt, &head, mnt_hash) + if (mnt->mnt_ex_mountpoint.mnt) + mntget(mnt->mnt_ex_mountpoint.mnt); + up_write(&namespace_sem); synchronize_rcu(); @@ -1268,6 +1273,7 @@ void umount_tree(struct mount *mnt, int how) p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; if (mnt_has_parent(p)) { put_mountpoint(p->mnt_mp); + mnt_add_count(p->mnt_parent, -1); /* move the reference to mountpoint into ->mnt_ex_mountpoint */ p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint; p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt; -- cgit v1.2.3