From 298fc1acf0a02dbd9bf6f21c40c68093670c1f4b Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sun, 22 Sep 2013 19:37:01 -0700 Subject: [PATCH] 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. Reviewed-by: Miklos Szeredi Signed-off-by: Eric W. Biederman --- fs/mount.h | 2 ++ fs/namespace.c | 6 ++++++ 2 files changed, 8 insertions(+) diff --git a/fs/mount.h b/fs/mount.h index 18511835dc28..5375da0dc570 100644 --- a/fs/mount.h +++ b/fs/mount.h @@ -21,6 +21,7 @@ struct mnt_pcp { struct mountpoint { struct list_head m_hash; struct dentry *m_dentry; + struct list_head m_list; int m_count; }; @@ -48,6 +49,7 @@ struct mount { 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 list_head 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 abe2f56efaea..32d380eabdac 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -195,6 +195,7 @@ static struct mount *alloc_vfsmnt(const char *name) INIT_LIST_HEAD(&mnt->mnt_share); INIT_LIST_HEAD(&mnt->mnt_slave_list); INIT_LIST_HEAD(&mnt->mnt_slave); + INIT_LIST_HEAD(&mnt->mnt_mp_list); #ifdef CONFIG_FSNOTIFY INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); #endif @@ -695,6 +696,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) mp->m_dentry = dentry; mp->m_count = 1; list_add(&mp->m_hash, chain); + INIT_LIST_HEAD(&mp->m_list); return mp; } @@ -702,6 +704,7 @@ static void put_mountpoint(struct mountpoint *mp) { if (!--mp->m_count) { struct dentry *dentry = mp->m_dentry; + BUG_ON(!list_empty(&mp->m_list)); spin_lock(&dentry->d_lock); dentry->d_flags &= ~DCACHE_MOUNTED; spin_unlock(&dentry->d_lock); @@ -748,6 +751,7 @@ static void detach_mnt(struct mount *mnt, struct path *old_path) mnt->mnt_mountpoint = mnt->mnt.mnt_root; list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_hash); + list_del_init(&mnt->mnt_mp_list); put_mountpoint(mnt->mnt_mp); mnt->mnt_mp = NULL; } @@ -764,6 +768,7 @@ void mnt_set_mountpoint(struct mount *mnt, child_mnt->mnt_mountpoint = dget(mp->m_dentry); child_mnt->mnt_parent = mnt; child_mnt->mnt_mp = mp; + list_add_tail(&child_mnt->mnt_mp_list, &mp->m_list); } /* @@ -1246,6 +1251,7 @@ void umount_tree(struct mount *mnt, int how) p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; list_del_init(&p->mnt_child); if (mnt_has_parent(p)) { + list_del_init(&p->mnt_mp_list); put_mountpoint(p->mnt_mp); /* move the reference to mountpoint into ->mnt_ex_mountpoint */ p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint; -- 2.39.5