Unverified Commit bf630c40 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Christian Brauner
Browse files

vfs: add notifications for mount attach and detach 



Add notifications for attaching and detaching mounts to fs/namespace.c

Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Link: https://lore.kernel.org/r/20250129165803.72138-4-mszeredi@redhat.com


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 0f46d81f

fs/mount.h

+20 −0
Original line number Diff line number Diff line
@@ -5,6 +5,8 @@ 
#include <linux/ns_common.h>

#include <linux/fs_pin.h>



extern struct list_head notify_list;



struct mnt_namespace {

	struct ns_common	ns;

	struct mount *	root;
@@ -80,6 +82,8 @@ struct mount { 
#ifdef CONFIG_FSNOTIFY

	struct fsnotify_mark_connector __rcu *mnt_fsnotify_marks;

	__u32 mnt_fsnotify_mask;

	struct list_head to_notify;	/* need to queue notification */

	struct mnt_namespace *prev_ns;	/* previous namespace (NULL if none) */

#endif

	int mnt_id;			/* mount identifier, reused */

	u64 mnt_id_unique;		/* mount ID unique until reboot */
@@ -182,4 +186,20 @@ static inline struct mnt_namespace *to_mnt_ns(struct ns_common *ns) 
	return container_of(ns, struct mnt_namespace, ns);

}



#ifdef CONFIG_FSNOTIFY

static inline void mnt_notify_add(struct mount *m)

{

	/* Optimize the case where there are no watches */

	if ((m->mnt_ns && m->mnt_ns->n_fsnotify_marks) ||

	    (m->prev_ns && m->prev_ns->n_fsnotify_marks))

		list_add_tail(&m->to_notify, &notify_list);

	else

		m->prev_ns = m->mnt_ns;

}

#else

static inline void mnt_notify_add(struct mount *m)

{

}

#endif



struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry);

fs/namespace.c

+78 −1
Original line number Diff line number Diff line
@@ -81,6 +81,9 @@ static HLIST_HEAD(unmounted); /* protected by namespace_sem */ 
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */

static DEFINE_SEQLOCK(mnt_ns_tree_lock);



#ifdef CONFIG_FSNOTIFY

LIST_HEAD(notify_list); /* protected by namespace_sem */

#endif

static struct rb_root mnt_ns_tree = RB_ROOT; /* protected by mnt_ns_tree_lock */

static LIST_HEAD(mnt_ns_list); /* protected by mnt_ns_tree_lock */
@@ -163,6 +166,7 @@ static void mnt_ns_release(struct mnt_namespace *ns) 
{

	/* keep alive for {list,stat}mount() */

	if (refcount_dec_and_test(&ns->passive)) {

		fsnotify_mntns_delete(ns);

		put_user_ns(ns->user_ns);

		kfree(ns);

	}
@@ -1176,6 +1180,8 @@ static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt) 
		ns->mnt_first_node = &mnt->mnt_node;

	rb_link_node(&mnt->mnt_node, parent, link);

	rb_insert_color(&mnt->mnt_node, &ns->mounts);



	mnt_notify_add(mnt);

}



/*
@@ -1723,6 +1729,50 @@ int may_umount(struct vfsmount *mnt) 


EXPORT_SYMBOL(may_umount);



#ifdef CONFIG_FSNOTIFY

static void mnt_notify(struct mount *p)

{

	if (!p->prev_ns && p->mnt_ns) {

		fsnotify_mnt_attach(p->mnt_ns, &p->mnt);

	} else if (p->prev_ns && !p->mnt_ns) {

		fsnotify_mnt_detach(p->prev_ns, &p->mnt);

	} else if (p->prev_ns == p->mnt_ns) {

		fsnotify_mnt_move(p->mnt_ns, &p->mnt);

	} else {

		fsnotify_mnt_detach(p->prev_ns, &p->mnt);

		fsnotify_mnt_attach(p->mnt_ns, &p->mnt);

	}

	p->prev_ns = p->mnt_ns;

}



static void notify_mnt_list(void)

{

	struct mount *m, *tmp;

	/*

	 * Notify about mounts that were added/reparented/detached/remain

	 * connected after unmount.

	 */

	list_for_each_entry_safe(m, tmp, &notify_list, to_notify) {

		mnt_notify(m);

		list_del_init(&m->to_notify);

	}

}



static bool need_notify_mnt_list(void)

{

	return !list_empty(&notify_list);

}

#else

static void notify_mnt_list(void)

{

}



static bool need_notify_mnt_list(void)

{

	return false;

}

#endif



static void namespace_unlock(void)

{

	struct hlist_head head;
@@ -1733,7 +1783,18 @@ static void namespace_unlock(void) 
	hlist_move_list(&unmounted, &head);

	list_splice_init(&ex_mountpoints, &list);



	if (need_notify_mnt_list()) {

		/*

		 * No point blocking out concurrent readers while notifications

		 * are sent. This will also allow statmount()/listmount() to run

		 * concurrently.

		 */

		downgrade_write(&namespace_sem);

		notify_mnt_list();

		up_read(&namespace_sem);

	} else {

		up_write(&namespace_sem);

	}



	shrink_dentry_list(&list);
@@ -1846,6 +1907,19 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) 
		change_mnt_propagation(p, MS_PRIVATE);

		if (disconnect)

			hlist_add_head(&p->mnt_umount, &unmounted);



		/*

		 * At this point p->mnt_ns is NULL, notification will be queued

		 * only if

		 *

		 *  - p->prev_ns is non-NULL *and*

		 *  - p->prev_ns->n_fsnotify_marks is non-NULL

		 *

		 * This will preclude queuing the mount if this is a cleanup

		 * after a failed copy_tree() or destruction of an anonymous

		 * namespace, etc.

		 */

		mnt_notify_add(p);

	}

}
@@ -2555,6 +2629,7 @@ static int attach_recursive_mnt(struct mount *source_mnt, 
			dest_mp = smp;

		unhash_mnt(source_mnt);

		attach_mnt(source_mnt, top_mnt, dest_mp, beneath);

		mnt_notify_add(source_mnt);

		touch_mnt_namespace(source_mnt->mnt_ns);

	} else {

		if (source_mnt->mnt_ns) {
@@ -4476,6 +4551,8 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 
	list_del_init(&new_mnt->mnt_expire);

	put_mountpoint(root_mp);

	unlock_mount_hash();

	mnt_notify_add(root_mnt);

	mnt_notify_add(new_mnt);

	chroot_fs_refs(&root, &new);

	error = 0;

out4:

fs/pnode.c

+3 −1
Original line number Diff line number Diff line
@@ -549,8 +549,10 @@ static void restore_mounts(struct list_head *to_restore) 
			mp = parent->mnt_mp;

			parent = parent->mnt_parent;

		}

		if (parent != mnt->mnt_parent)

		if (parent != mnt->mnt_parent) {

			mnt_change_mountpoint(parent, mp, mnt);

			mnt_notify_add(mnt);

		}

	}

}