Commit afac7cba authored by Al Viro's avatar Al Viro
Browse files

vfs: more mnt_parent cleanups 



a) mount --move is checking that ->mnt_parent is non-NULL before
looking if that parent happens to be shared; ->mnt_parent is never
NULL and it's not even an misspelled !mnt_has_parent()

b) pivot_root open-codes is_path_reachable(), poorly.

c) so does path_is_under(), while we are at it.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent b2dba1af

fs/dcache.c

+0 −25
Original line number Diff line number Diff line
@@ -2853,31 +2853,6 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry) 
	return result;

}



int path_is_under(struct path *path1, struct path *path2)

{

	struct vfsmount *mnt = path1->mnt;

	struct dentry *dentry = path1->dentry;

	int res;



	br_read_lock(vfsmount_lock);

	if (mnt != path2->mnt) {

		for (;;) {

			if (!mnt_has_parent(mnt)) {

				br_read_unlock(vfsmount_lock);

				return 0;

			}

			if (mnt->mnt_parent == path2->mnt)

				break;

			mnt = mnt->mnt_parent;

		}

		dentry = mnt->mnt_mountpoint;

	}

	res = is_subdir(dentry, path2->dentry);

	br_read_unlock(vfsmount_lock);

	return res;

}

EXPORT_SYMBOL(path_is_under);



void d_genocide(struct dentry *root)

{

	struct dentry *this_parent;

fs/namespace.c

+27 −15
Original line number Diff line number Diff line
@@ -1876,8 +1876,7 @@ static int do_move_mount(struct path *path, char *old_name) 
	/*

	 * Don't move a mount residing in a shared parent.

	 */

	if (old_path.mnt->mnt_parent &&

	    IS_MNT_SHARED(old_path.mnt->mnt_parent))

	if (IS_MNT_SHARED(old_path.mnt->mnt_parent))

		goto out1;

	/*

	 * Don't move a mount tree containing unbindable mounts to a destination
@@ -2533,6 +2532,31 @@ out_type: 
	return ret;

}



/*

 * Return true if path is reachable from root

 *

 * namespace_sem or vfsmount_lock is held

 */

bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,

			 const struct path *root)

{

	while (mnt != root->mnt && mnt_has_parent(mnt)) {

		dentry = mnt->mnt_mountpoint;

		mnt = mnt->mnt_parent;

	}

	return mnt == root->mnt && is_subdir(dentry, root->dentry);

}



int path_is_under(struct path *path1, struct path *path2)

{

	int res;

	br_read_lock(vfsmount_lock);

	res = is_path_reachable(path1->mnt, path1->dentry, path2);

	br_read_unlock(vfsmount_lock);

	return res;

}

EXPORT_SYMBOL(path_is_under);



/*

 * pivot_root Semantics:

 * Moves the root file system of the current process to the directory put_old,
@@ -2561,7 +2585,6 @@ out_type: 
SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,

		const char __user *, put_old)

{

	struct vfsmount *tmp;

	struct path new, old, parent_path, root_parent, root;

	int error;
@@ -2611,18 +2634,7 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 
	if (!mnt_has_parent(new.mnt))

		goto out4; /* not attached */

	/* make sure we can reach put_old from new_root */

	tmp = old.mnt;

	if (tmp != new.mnt) {

		for (;;) {

			if (!mnt_has_parent(tmp))

				goto out4; /* already mounted on put_old */

			if (tmp->mnt_parent == new.mnt)

				break;

			tmp = tmp->mnt_parent;

		}

		if (!is_subdir(tmp->mnt_mountpoint, new.dentry))

			goto out4;

	} else if (!is_subdir(old.dentry, new.dentry))

	if (!is_path_reachable(old.mnt, old.dentry, &new))

		goto out4;

	br_write_lock(vfsmount_lock);

	detach_mnt(new.mnt, &parent_path);

fs/pnode.c

+0 −15
Original line number Diff line number Diff line
@@ -28,21 +28,6 @@ static inline struct vfsmount *next_slave(struct vfsmount *p) 
	return list_entry(p->mnt_slave.next, struct vfsmount, mnt_slave);

}



/*

 * Return true if path is reachable from root

 *

 * namespace_sem is held, and mnt is attached

 */

static bool is_path_reachable(struct vfsmount *mnt, struct dentry *dentry,

			 const struct path *root)

{

	while (mnt != root->mnt && mnt_has_parent(mnt)) {

		dentry = mnt->mnt_mountpoint;

		mnt = mnt->mnt_parent;

	}

	return mnt == root->mnt && is_subdir(dentry, root->dentry);

}



static struct vfsmount *get_peer_under_root(struct vfsmount *mnt,

					    struct mnt_namespace *ns,

					    const struct path *root)

fs/pnode.h

+2 −0
Original line number Diff line number Diff line
@@ -42,4 +42,6 @@ void mnt_set_mountpoint(struct vfsmount *, struct dentry *, 
void release_mounts(struct list_head *);

void umount_tree(struct vfsmount *, int, struct list_head *);

struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int);

bool is_path_reachable(struct vfsmount *, struct dentry *,

			 const struct path *root);

#endif /* _LINUX_PNODE_H */

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