Commit 0a5eb7c8 authored by Eric W. Biederman's avatar Eric W. Biederman Committed by Al Viro
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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: default avatarMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: default avatarEric W. Biederman <ebiederman@twitter.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 7af1364f

fs/mount.h

+2 −0
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ struct mnt_pcp { 
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 { 
	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;

fs/namespace.c

+6 −0
Original line number Diff line number Diff line
@@ -225,6 +225,7 @@ 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_HLIST_NODE(&mnt->mnt_mp_list);

#ifdef CONFIG_FSNOTIFY

		INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);

#endif
@@ -731,6 +732,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry) 
	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 @@ static void put_mountpoint(struct mountpoint *mp) 
{

	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 @@ static void detach_mnt(struct mount *mnt, struct path *old_path) 
	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 @@ 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;

	hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);

}



/*
@@ -1342,6 +1347,7 @@ void umount_tree(struct mount *mnt, int how) 
		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 */