vfs: Keep a list of mounts on a mount point
To spot any possible problems call BUG if a mountpoint
is put when it's list of mounts is not empty.
AV: use hlist instead of list_head
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Eric W. Biederman <ebiederman@twitter.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/mount.h b/fs/mount.h
index 8c6a2a6..68bb03e 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -21,6 +21,7 @@
struct mountpoint {
struct hlist_node m_hash;
struct dentry *m_dentry;
+ struct hlist_head m_list;
int m_count;
};
@@ -51,6 +52,7 @@
struct mount *mnt_master; /* slave is on master->mnt_slave_list */
struct mnt_namespace *mnt_ns; /* containing namespace */
struct mountpoint *mnt_mp; /* where is it mounted */
+ struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */
#ifdef CONFIG_FSNOTIFY
struct hlist_head mnt_fsnotify_marks;
__u32 mnt_fsnotify_mask;
diff --git a/fs/namespace.c b/fs/namespace.c
index 77ffdb8..99572dd 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -225,6 +225,7 @@
INIT_LIST_HEAD(&mnt->mnt_share);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
INIT_LIST_HEAD(&mnt->mnt_slave);
+ INIT_HLIST_NODE(&mnt->mnt_mp_list);
#ifdef CONFIG_FSNOTIFY
INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
#endif
@@ -731,6 +732,7 @@
mp->m_dentry = dentry;
mp->m_count = 1;
hlist_add_head(&mp->m_hash, chain);
+ INIT_HLIST_HEAD(&mp->m_list);
return mp;
}
@@ -738,6 +740,7 @@
{
if (!--mp->m_count) {
struct dentry *dentry = mp->m_dentry;
+ BUG_ON(!hlist_empty(&mp->m_list));
spin_lock(&dentry->d_lock);
dentry->d_flags &= ~DCACHE_MOUNTED;
spin_unlock(&dentry->d_lock);
@@ -784,6 +787,7 @@
mnt->mnt_mountpoint = mnt->mnt.mnt_root;
list_del_init(&mnt->mnt_child);
hlist_del_init_rcu(&mnt->mnt_hash);
+ hlist_del_init(&mnt->mnt_mp_list);
put_mountpoint(mnt->mnt_mp);
mnt->mnt_mp = NULL;
}
@@ -800,6 +804,7 @@
child_mnt->mnt_mountpoint = dget(mp->m_dentry);
child_mnt->mnt_parent = mnt;
child_mnt->mnt_mp = mp;
+ hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
}
/*
@@ -1342,6 +1347,7 @@
if (how < 2)
p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
if (mnt_has_parent(p)) {
+ hlist_del_init(&p->mnt_mp_list);
put_mountpoint(p->mnt_mp);
mnt_add_count(p->mnt_parent, -1);
/* move the reference to mountpoint into ->mnt_ex_mountpoint */