Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 911 insertions, 0 deletions

diff --git a/fs/notify/mark.c b/fs/notify/mark.c
new file mode 100644
index 0000000000..c74ef94744
--- /dev/null
+++ b/fs/notify/mark.c
@@ -0,0 +1,911 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
+ */
+
+/*
+ * fsnotify inode mark locking/lifetime/and refcnting
+ *
+ * REFCNT:
+ * The group->recnt and mark->refcnt tell how many "things" in the kernel
+ * currently are referencing the objects. Both kind of objects typically will
+ * live inside the kernel with a refcnt of 2, one for its creation and one for
+ * the reference a group and a mark hold to each other.
+ * If you are holding the appropriate locks, you can take a reference and the
+ * object itself is guaranteed to survive until the reference is dropped.
+ *
+ * LOCKING:
+ * There are 3 locks involved with fsnotify inode marks and they MUST be taken
+ * in order as follows:
+ *
+ * group->mark_mutex
+ * mark->lock
+ * mark->connector->lock
+ *
+ * group->mark_mutex protects the marks_list anchored inside a given group and
+ * each mark is hooked via the g_list.  It also protects the groups private
+ * data (i.e group limits).
+
+ * mark->lock protects the marks attributes like its masks and flags.
+ * Furthermore it protects the access to a reference of the group that the mark
+ * is assigned to as well as the access to a reference of the inode/vfsmount
+ * that is being watched by the mark.
+ *
+ * mark->connector->lock protects the list of marks anchored inside an
+ * inode / vfsmount and each mark is hooked via the i_list.
+ *
+ * A list of notification marks relating to inode / mnt is contained in
+ * fsnotify_mark_connector. That structure is alive as long as there are any
+ * marks in the list and is also protected by fsnotify_mark_srcu. A mark gets
+ * detached from fsnotify_mark_connector when last reference to the mark is
+ * dropped.  Thus having mark reference is enough to protect mark->connector
+ * pointer and to make sure fsnotify_mark_connector cannot disappear. Also
+ * because we remove mark from g_list before dropping mark reference associated
+ * with that, any mark found through g_list is guaranteed to have
+ * mark->connector set until we drop group->mark_mutex.
+ *
+ * LIFETIME:
+ * Inode marks survive between when they are added to an inode and when their
+ * refcnt==0. Marks are also protected by fsnotify_mark_srcu.
+ *
+ * The inode mark can be cleared for a number of different reasons including:
+ * - The inode is unlinked for the last time.  (fsnotify_inode_remove)
+ * - The inode is being evicted from cache. (fsnotify_inode_delete)
+ * - The fs the inode is on is unmounted.  (fsnotify_inode_delete/fsnotify_unmount_inodes)
+ * - Something explicitly requests that it be removed.  (fsnotify_destroy_mark)
+ * - The fsnotify_group associated with the mark is going away and all such marks
+ *   need to be cleaned up. (fsnotify_clear_marks_by_group)
+ *
+ * This has the very interesting property of being able to run concurrently with
+ * any (or all) other directions.
+ */
+
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/srcu.h>
+#include <linux/ratelimit.h>
+
+#include <linux/atomic.h>
+
+#include <linux/fsnotify_backend.h>
+#include "fsnotify.h"
+
+#define FSNOTIFY_REAPER_DELAY	(1)	/* 1 jiffy */
+
+struct srcu_struct fsnotify_mark_srcu;
+struct kmem_cache *fsnotify_mark_connector_cachep;
+
+static DEFINE_SPINLOCK(destroy_lock);
+static LIST_HEAD(destroy_list);
+static struct fsnotify_mark_connector *connector_destroy_list;
+
+static void fsnotify_mark_destroy_workfn(struct work_struct *work);
+static DECLARE_DELAYED_WORK(reaper_work, fsnotify_mark_destroy_workfn);
+
+static void fsnotify_connector_destroy_workfn(struct work_struct *work);
+static DECLARE_WORK(connector_reaper_work, fsnotify_connector_destroy_workfn);
+
+void fsnotify_get_mark(struct fsnotify_mark *mark)
+{
+	WARN_ON_ONCE(!refcount_read(&mark->refcnt));
+	refcount_inc(&mark->refcnt);
+}
+
+static __u32 *fsnotify_conn_mask_p(struct fsnotify_mark_connector *conn)
+{
+	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
+		return &fsnotify_conn_inode(conn)->i_fsnotify_mask;
+	else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT)
+		return &fsnotify_conn_mount(conn)->mnt_fsnotify_mask;
+	else if (conn->type == FSNOTIFY_OBJ_TYPE_SB)
+		return &fsnotify_conn_sb(conn)->s_fsnotify_mask;
+	return NULL;
+}
+
+__u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn)
+{
+	if (WARN_ON(!fsnotify_valid_obj_type(conn->type)))
+		return 0;
+
+	return *fsnotify_conn_mask_p(conn);
+}
+
+static void fsnotify_get_inode_ref(struct inode *inode)
+{
+	ihold(inode);
+	atomic_long_inc(&inode->i_sb->s_fsnotify_connectors);
+}
+
+/*
+ * Grab or drop inode reference for the connector if needed.
+ *
+ * When it's time to drop the reference, we only clear the HAS_IREF flag and
+ * return the inode object. fsnotify_drop_object() will be resonsible for doing
+ * iput() outside of spinlocks. This happens when last mark that wanted iref is
+ * detached.
+ */
+static struct inode *fsnotify_update_iref(struct fsnotify_mark_connector *conn,
+					  bool want_iref)
+{
+	bool has_iref = conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF;
+	struct inode *inode = NULL;
+
+	if (conn->type != FSNOTIFY_OBJ_TYPE_INODE ||
+	    want_iref == has_iref)
+		return NULL;
+
+	if (want_iref) {
+		/* Pin inode if any mark wants inode refcount held */
+		fsnotify_get_inode_ref(fsnotify_conn_inode(conn));
+		conn->flags |= FSNOTIFY_CONN_FLAG_HAS_IREF;
+	} else {
+		/* Unpin inode after detach of last mark that wanted iref */
+		inode = fsnotify_conn_inode(conn);
+		conn->flags &= ~FSNOTIFY_CONN_FLAG_HAS_IREF;
+	}
+
+	return inode;
+}
+
+static void *__fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
+{
+	u32 new_mask = 0;
+	bool want_iref = false;
+	struct fsnotify_mark *mark;
+
+	assert_spin_locked(&conn->lock);
+	/* We can get detached connector here when inode is getting unlinked. */
+	if (!fsnotify_valid_obj_type(conn->type))
+		return NULL;
+	hlist_for_each_entry(mark, &conn->list, obj_list) {
+		if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED))
+			continue;
+		new_mask |= fsnotify_calc_mask(mark);
+		if (conn->type == FSNOTIFY_OBJ_TYPE_INODE &&
+		    !(mark->flags & FSNOTIFY_MARK_FLAG_NO_IREF))
+			want_iref = true;
+	}
+	*fsnotify_conn_mask_p(conn) = new_mask;
+
+	return fsnotify_update_iref(conn, want_iref);
+}
+
+/*
+ * Calculate mask of events for a list of marks. The caller must make sure
+ * connector and connector->obj cannot disappear under us.  Callers achieve
+ * this by holding a mark->lock or mark->group->mark_mutex for a mark on this
+ * list.
+ */
+void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn)
+{
+	if (!conn)
+		return;
+
+	spin_lock(&conn->lock);
+	__fsnotify_recalc_mask(conn);
+	spin_unlock(&conn->lock);
+	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE)
+		__fsnotify_update_child_dentry_flags(
+					fsnotify_conn_inode(conn));
+}
+
+/* Free all connectors queued for freeing once SRCU period ends */
+static void fsnotify_connector_destroy_workfn(struct work_struct *work)
+{
+	struct fsnotify_mark_connector *conn, *free;
+
+	spin_lock(&destroy_lock);
+	conn = connector_destroy_list;
+	connector_destroy_list = NULL;
+	spin_unlock(&destroy_lock);
+
+	synchronize_srcu(&fsnotify_mark_srcu);
+	while (conn) {
+		free = conn;
+		conn = conn->destroy_next;
+		kmem_cache_free(fsnotify_mark_connector_cachep, free);
+	}
+}
+
+static void fsnotify_put_inode_ref(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+
+	iput(inode);
+	if (atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
+		wake_up_var(&sb->s_fsnotify_connectors);
+}
+
+static void fsnotify_get_sb_connectors(struct fsnotify_mark_connector *conn)
+{
+	struct super_block *sb = fsnotify_connector_sb(conn);
+
+	if (sb)
+		atomic_long_inc(&sb->s_fsnotify_connectors);
+}
+
+static void fsnotify_put_sb_connectors(struct fsnotify_mark_connector *conn)
+{
+	struct super_block *sb = fsnotify_connector_sb(conn);
+
+	if (sb && atomic_long_dec_and_test(&sb->s_fsnotify_connectors))
+		wake_up_var(&sb->s_fsnotify_connectors);
+}
+
+static void *fsnotify_detach_connector_from_object(
+					struct fsnotify_mark_connector *conn,
+					unsigned int *type)
+{
+	struct inode *inode = NULL;
+
+	*type = conn->type;
+	if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED)
+		return NULL;
+
+	if (conn->type == FSNOTIFY_OBJ_TYPE_INODE) {
+		inode = fsnotify_conn_inode(conn);
+		inode->i_fsnotify_mask = 0;
+
+		/* Unpin inode when detaching from connector */
+		if (!(conn->flags & FSNOTIFY_CONN_FLAG_HAS_IREF))
+			inode = NULL;
+	} else if (conn->type == FSNOTIFY_OBJ_TYPE_VFSMOUNT) {
+		fsnotify_conn_mount(conn)->mnt_fsnotify_mask = 0;
+	} else if (conn->type == FSNOTIFY_OBJ_TYPE_SB) {
+		fsnotify_conn_sb(conn)->s_fsnotify_mask = 0;
+	}
+
+	fsnotify_put_sb_connectors(conn);
+	rcu_assign_pointer(*(conn->obj), NULL);
+	conn->obj = NULL;
+	conn->type = FSNOTIFY_OBJ_TYPE_DETACHED;
+
+	return inode;
+}
+
+static void fsnotify_final_mark_destroy(struct fsnotify_mark *mark)
+{
+	struct fsnotify_group *group = mark->group;
+
+	if (WARN_ON_ONCE(!group))
+		return;
+	group->ops->free_mark(mark);
+	fsnotify_put_group(group);
+}
+
+/* Drop object reference originally held by a connector */
+static void fsnotify_drop_object(unsigned int type, void *objp)
+{
+	if (!objp)
+		return;
+	/* Currently only inode references are passed to be dropped */
+	if (WARN_ON_ONCE(type != FSNOTIFY_OBJ_TYPE_INODE))
+		return;
+	fsnotify_put_inode_ref(objp);
+}
+
+void fsnotify_put_mark(struct fsnotify_mark *mark)
+{
+	struct fsnotify_mark_connector *conn = READ_ONCE(mark->connector);
+	void *objp = NULL;
+	unsigned int type = FSNOTIFY_OBJ_TYPE_DETACHED;
+	bool free_conn = false;
+
+	/* Catch marks that were actually never attached to object */
+	if (!conn) {
+		if (refcount_dec_and_test(&mark->refcnt))
+			fsnotify_final_mark_destroy(mark);
+		return;
+	}
+
+	/*
+	 * We have to be careful so that traversals of obj_list under lock can
+	 * safely grab mark reference.
+	 */
+	if (!refcount_dec_and_lock(&mark->refcnt, &conn->lock))
+		return;
+
+	hlist_del_init_rcu(&mark->obj_list);
+	if (hlist_empty(&conn->list)) {
+		objp = fsnotify_detach_connector_from_object(conn, &type);
+		free_conn = true;
+	} else {
+		objp = __fsnotify_recalc_mask(conn);
+		type = conn->type;
+	}
+	WRITE_ONCE(mark->connector, NULL);
+	spin_unlock(&conn->lock);
+
+	fsnotify_drop_object(type, objp);
+
+	if (free_conn) {
+		spin_lock(&destroy_lock);
+		conn->destroy_next = connector_destroy_list;
+		connector_destroy_list = conn;
+		spin_unlock(&destroy_lock);
+		queue_work(system_unbound_wq, &connector_reaper_work);
+	}
+	/*
+	 * Note that we didn't update flags telling whether inode cares about
+	 * what's happening with children. We update these flags from
+	 * __fsnotify_parent() lazily when next event happens on one of our
+	 * children.
+	 */
+	spin_lock(&destroy_lock);
+	list_add(&mark->g_list, &destroy_list);
+	spin_unlock(&destroy_lock);
+	queue_delayed_work(system_unbound_wq, &reaper_work,
+			   FSNOTIFY_REAPER_DELAY);
+}
+EXPORT_SYMBOL_GPL(fsnotify_put_mark);
+
+/*
+ * Get mark reference when we found the mark via lockless traversal of object
+ * list. Mark can be already removed from the list by now and on its way to be
+ * destroyed once SRCU period ends.
+ *
+ * Also pin the group so it doesn't disappear under us.
+ */
+static bool fsnotify_get_mark_safe(struct fsnotify_mark *mark)
+{
+	if (!mark)
+		return true;
+
+	if (refcount_inc_not_zero(&mark->refcnt)) {
+		spin_lock(&mark->lock);
+		if (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) {
+			/* mark is attached, group is still alive then */
+			atomic_inc(&mark->group->user_waits);
+			spin_unlock(&mark->lock);
+			return true;
+		}
+		spin_unlock(&mark->lock);
+		fsnotify_put_mark(mark);
+	}
+	return false;
+}
+
+/*
+ * Puts marks and wakes up group destruction if necessary.
+ *
+ * Pairs with fsnotify_get_mark_safe()
+ */
+static void fsnotify_put_mark_wake(struct fsnotify_mark *mark)
+{
+	if (mark) {
+		struct fsnotify_group *group = mark->group;
+
+		fsnotify_put_mark(mark);
+		/*
+		 * We abuse notification_waitq on group shutdown for waiting for
+		 * all marks pinned when waiting for userspace.
+		 */
+		if (atomic_dec_and_test(&group->user_waits) && group->shutdown)
+			wake_up(&group->notification_waitq);
+	}
+}
+
+bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info)
+	__releases(&fsnotify_mark_srcu)
+{
+	int type;
+
+	fsnotify_foreach_iter_type(type) {
+		/* This can fail if mark is being removed */
+		if (!fsnotify_get_mark_safe(iter_info->marks[type])) {
+			__release(&fsnotify_mark_srcu);
+			goto fail;
+		}
+	}
+
+	/*
+	 * Now that both marks are pinned by refcount in the inode / vfsmount
+	 * lists, we can drop SRCU lock, and safely resume the list iteration
+	 * once userspace returns.
+	 */
+	srcu_read_unlock(&fsnotify_mark_srcu, iter_info->srcu_idx);
+
+	return true;
+
+fail:
+	for (type--; type >= 0; type--)
+		fsnotify_put_mark_wake(iter_info->marks[type]);
+	return false;
+}
+
+void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
+	__acquires(&fsnotify_mark_srcu)
+{
+	int type;
+
+	iter_info->srcu_idx = srcu_read_lock(&fsnotify_mark_srcu);
+	fsnotify_foreach_iter_type(type)
+		fsnotify_put_mark_wake(iter_info->marks[type]);
+}
+
+/*
+ * Mark mark as detached, remove it from group list. Mark still stays in object
+ * list until its last reference is dropped. Note that we rely on mark being
+ * removed from group list before corresponding reference to it is dropped. In
+ * particular we rely on mark->connector being valid while we hold
+ * group->mark_mutex if we found the mark through g_list.
+ *
+ * Must be called with group->mark_mutex held. The caller must either hold
+ * reference to the mark or be protected by fsnotify_mark_srcu.
+ */
+void fsnotify_detach_mark(struct fsnotify_mark *mark)
+{
+	fsnotify_group_assert_locked(mark->group);
+	WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
+		     refcount_read(&mark->refcnt) < 1 +
+			!!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
+
+	spin_lock(&mark->lock);
+	/* something else already called this function on this mark */
+	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
+		spin_unlock(&mark->lock);
+		return;
+	}
+	mark->flags &= ~FSNOTIFY_MARK_FLAG_ATTACHED;
+	list_del_init(&mark->g_list);
+	spin_unlock(&mark->lock);
+
+	/* Drop mark reference acquired in fsnotify_add_mark_locked() */
+	fsnotify_put_mark(mark);
+}
+
+/*
+ * Free fsnotify mark. The mark is actually only marked as being freed.  The
+ * freeing is actually happening only once last reference to the mark is
+ * dropped from a workqueue which first waits for srcu period end.
+ *
+ * Caller must have a reference to the mark or be protected by
+ * fsnotify_mark_srcu.
+ */
+void fsnotify_free_mark(struct fsnotify_mark *mark)
+{
+	struct fsnotify_group *group = mark->group;
+
+	spin_lock(&mark->lock);
+	/* something else already called this function on this mark */
+	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
+		spin_unlock(&mark->lock);
+		return;
+	}
+	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
+	spin_unlock(&mark->lock);
+
+	/*
+	 * Some groups like to know that marks are being freed.  This is a
+	 * callback to the group function to let it know that this mark
+	 * is being freed.
+	 */
+	if (group->ops->freeing_mark)
+		group->ops->freeing_mark(mark, group);
+}
+
+void fsnotify_destroy_mark(struct fsnotify_mark *mark,
+			   struct fsnotify_group *group)
+{
+	fsnotify_group_lock(group);
+	fsnotify_detach_mark(mark);
+	fsnotify_group_unlock(group);
+	fsnotify_free_mark(mark);
+}
+EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
+
+/*
+ * Sorting function for lists of fsnotify marks.
+ *
+ * Fanotify supports different notification classes (reflected as priority of
+ * notification group). Events shall be passed to notification groups in
+ * decreasing priority order. To achieve this marks in notification lists for
+ * inodes and vfsmounts are sorted so that priorities of corresponding groups
+ * are descending.
+ *
+ * Furthermore correct handling of the ignore mask requires processing inode
+ * and vfsmount marks of each group together. Using the group address as
+ * further sort criterion provides a unique sorting order and thus we can
+ * merge inode and vfsmount lists of marks in linear time and find groups
+ * present in both lists.
+ *
+ * A return value of 1 signifies that b has priority over a.
+ * A return value of 0 signifies that the two marks have to be handled together.
+ * A return value of -1 signifies that a has priority over b.
+ */
+int fsnotify_compare_groups(struct fsnotify_group *a, struct fsnotify_group *b)
+{
+	if (a == b)
+		return 0;
+	if (!a)
+		return 1;
+	if (!b)
+		return -1;
+	if (a->priority < b->priority)
+		return 1;
+	if (a->priority > b->priority)
+		return -1;
+	if (a < b)
+		return 1;
+	return -1;
+}
+
+static int fsnotify_attach_connector_to_object(fsnotify_connp_t *connp,
+					       unsigned int obj_type,
+					       __kernel_fsid_t *fsid)
+{
+	struct fsnotify_mark_connector *conn;
+
+	conn = kmem_cache_alloc(fsnotify_mark_connector_cachep, GFP_KERNEL);
+	if (!conn)
+		return -ENOMEM;
+	spin_lock_init(&conn->lock);
+	INIT_HLIST_HEAD(&conn->list);
+	conn->flags = 0;
+	conn->type = obj_type;
+	conn->obj = connp;
+	/* Cache fsid of filesystem containing the object */
+	if (fsid) {
+		conn->fsid = *fsid;
+		conn->flags = FSNOTIFY_CONN_FLAG_HAS_FSID;
+	} else {
+		conn->fsid.val[0] = conn->fsid.val[1] = 0;
+		conn->flags = 0;
+	}
+	fsnotify_get_sb_connectors(conn);
+
+	/*
+	 * cmpxchg() provides the barrier so that readers of *connp can see
+	 * only initialized structure
+	 */
+	if (cmpxchg(connp, NULL, conn)) {
+		/* Someone else created list structure for us */
+		fsnotify_put_sb_connectors(conn);
+		kmem_cache_free(fsnotify_mark_connector_cachep, conn);
+	}
+
+	return 0;
+}
+
+/*
+ * Get mark connector, make sure it is alive and return with its lock held.
+ * This is for users that get connector pointer from inode or mount. Users that
+ * hold reference to a mark on the list may directly lock connector->lock as
+ * they are sure list cannot go away under them.
+ */
+static struct fsnotify_mark_connector *fsnotify_grab_connector(
+						fsnotify_connp_t *connp)
+{
+	struct fsnotify_mark_connector *conn;
+	int idx;
+
+	idx = srcu_read_lock(&fsnotify_mark_srcu);
+	conn = srcu_dereference(*connp, &fsnotify_mark_srcu);
+	if (!conn)
+		goto out;
+	spin_lock(&conn->lock);
+	if (conn->type == FSNOTIFY_OBJ_TYPE_DETACHED) {
+		spin_unlock(&conn->lock);
+		srcu_read_unlock(&fsnotify_mark_srcu, idx);
+		return NULL;
+	}
+out:
+	srcu_read_unlock(&fsnotify_mark_srcu, idx);
+	return conn;
+}
+
+/*
+ * Add mark into proper place in given list of marks. These marks may be used
+ * for the fsnotify backend to determine which event types should be delivered
+ * to which group and for which inodes. These marks are ordered according to
+ * priority, highest number first, and then by the group's location in memory.
+ */
+static int fsnotify_add_mark_list(struct fsnotify_mark *mark,
+				  fsnotify_connp_t *connp,
+				  unsigned int obj_type,
+				  int add_flags, __kernel_fsid_t *fsid)
+{
+	struct fsnotify_mark *lmark, *last = NULL;
+	struct fsnotify_mark_connector *conn;
+	int cmp;
+	int err = 0;
+
+	if (WARN_ON(!fsnotify_valid_obj_type(obj_type)))
+		return -EINVAL;
+
+	/* Backend is expected to check for zero fsid (e.g. tmpfs) */
+	if (fsid && WARN_ON_ONCE(!fsid->val[0] && !fsid->val[1]))
+		return -ENODEV;
+
+restart:
+	spin_lock(&mark->lock);
+	conn = fsnotify_grab_connector(connp);
+	if (!conn) {
+		spin_unlock(&mark->lock);
+		err = fsnotify_attach_connector_to_object(connp, obj_type,
+							  fsid);
+		if (err)
+			return err;
+		goto restart;
+	} else if (fsid && !(conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID)) {
+		conn->fsid = *fsid;
+		/* Pairs with smp_rmb() in fanotify_get_fsid() */
+		smp_wmb();
+		conn->flags |= FSNOTIFY_CONN_FLAG_HAS_FSID;
+	} else if (fsid && (conn->flags & FSNOTIFY_CONN_FLAG_HAS_FSID) &&
+		   (fsid->val[0] != conn->fsid.val[0] ||
+		    fsid->val[1] != conn->fsid.val[1])) {
+		/*
+		 * Backend is expected to check for non uniform fsid
+		 * (e.g. btrfs), but maybe we missed something?
+		 * Only allow setting conn->fsid once to non zero fsid.
+		 * inotify and non-fid fanotify groups do not set nor test
+		 * conn->fsid.
+		 */
+		pr_warn_ratelimited("%s: fsid mismatch on object of type %u: "
+				    "%x.%x != %x.%x\n", __func__, conn->type,
+				    fsid->val[0], fsid->val[1],
+				    conn->fsid.val[0], conn->fsid.val[1]);
+		err = -EXDEV;
+		goto out_err;
+	}
+
+	/* is mark the first mark? */
+	if (hlist_empty(&conn->list)) {
+		hlist_add_head_rcu(&mark->obj_list, &conn->list);
+		goto added;
+	}
+
+	/* should mark be in the middle of the current list? */
+	hlist_for_each_entry(lmark, &conn->list, obj_list) {
+		last = lmark;
+
+		if ((lmark->group == mark->group) &&
+		    (lmark->flags & FSNOTIFY_MARK_FLAG_ATTACHED) &&
+		    !(mark->group->flags & FSNOTIFY_GROUP_DUPS)) {
+			err = -EEXIST;
+			goto out_err;
+		}
+
+		cmp = fsnotify_compare_groups(lmark->group, mark->group);
+		if (cmp >= 0) {
+			hlist_add_before_rcu(&mark->obj_list, &lmark->obj_list);
+			goto added;
+		}
+	}
+
+	BUG_ON(last == NULL);
+	/* mark should be the last entry.  last is the current last entry */
+	hlist_add_behind_rcu(&mark->obj_list, &last->obj_list);
+added:
+	/*
+	 * Since connector is attached to object using cmpxchg() we are
+	 * guaranteed that connector initialization is fully visible by anyone
+	 * seeing mark->connector set.
+	 */
+	WRITE_ONCE(mark->connector, conn);
+out_err:
+	spin_unlock(&conn->lock);
+	spin_unlock(&mark->lock);
+	return err;
+}
+
+/*
+ * Attach an initialized mark to a given group and fs object.
+ * These marks may be used for the fsnotify backend to determine which
+ * event types should be delivered to which group.
+ */
+int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
+			     fsnotify_connp_t *connp, unsigned int obj_type,
+			     int add_flags, __kernel_fsid_t *fsid)
+{
+	struct fsnotify_group *group = mark->group;
+	int ret = 0;
+
+	fsnotify_group_assert_locked(group);
+
+	/*
+	 * LOCKING ORDER!!!!
+	 * group->mark_mutex
+	 * mark->lock
+	 * mark->connector->lock
+	 */
+	spin_lock(&mark->lock);
+	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE | FSNOTIFY_MARK_FLAG_ATTACHED;
+
+	list_add(&mark->g_list, &group->marks_list);
+	fsnotify_get_mark(mark); /* for g_list */
+	spin_unlock(&mark->lock);
+
+	ret = fsnotify_add_mark_list(mark, connp, obj_type, add_flags, fsid);
+	if (ret)
+		goto err;
+
+	fsnotify_recalc_mask(mark->connector);
+
+	return ret;
+err:
+	spin_lock(&mark->lock);
+	mark->flags &= ~(FSNOTIFY_MARK_FLAG_ALIVE |
+			 FSNOTIFY_MARK_FLAG_ATTACHED);
+	list_del_init(&mark->g_list);
+	spin_unlock(&mark->lock);
+
+	fsnotify_put_mark(mark);
+	return ret;
+}
+
+int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
+		      unsigned int obj_type, int add_flags,
+		      __kernel_fsid_t *fsid)
+{
+	int ret;
+	struct fsnotify_group *group = mark->group;
+
+	fsnotify_group_lock(group);
+	ret = fsnotify_add_mark_locked(mark, connp, obj_type, add_flags, fsid);
+	fsnotify_group_unlock(group);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(fsnotify_add_mark);
+
+/*
+ * Given a list of marks, find the mark associated with given group. If found
+ * take a reference to that mark and return it, else return NULL.
+ */
+struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
+					 struct fsnotify_group *group)
+{
+	struct fsnotify_mark_connector *conn;
+	struct fsnotify_mark *mark;
+
+	conn = fsnotify_grab_connector(connp);
+	if (!conn)
+		return NULL;
+
+	hlist_for_each_entry(mark, &conn->list, obj_list) {
+		if (mark->group == group &&
+		    (mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED)) {
+			fsnotify_get_mark(mark);
+			spin_unlock(&conn->lock);
+			return mark;
+		}
+	}
+	spin_unlock(&conn->lock);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(fsnotify_find_mark);
+
+/* Clear any marks in a group with given type mask */
+void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
+				   unsigned int obj_type)
+{
+	struct fsnotify_mark *lmark, *mark;
+	LIST_HEAD(to_free);
+	struct list_head *head = &to_free;
+
+	/* Skip selection step if we want to clear all marks. */
+	if (obj_type == FSNOTIFY_OBJ_TYPE_ANY) {
+		head = &group->marks_list;
+		goto clear;
+	}
+	/*
+	 * We have to be really careful here. Anytime we drop mark_mutex, e.g.
+	 * fsnotify_clear_marks_by_inode() can come and free marks. Even in our
+	 * to_free list so we have to use mark_mutex even when accessing that
+	 * list. And freeing mark requires us to drop mark_mutex. So we can
+	 * reliably free only the first mark in the list. That's why we first
+	 * move marks to free to to_free list in one go and then free marks in
+	 * to_free list one by one.
+	 */
+	fsnotify_group_lock(group);
+	list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
+		if (mark->connector->type == obj_type)
+			list_move(&mark->g_list, &to_free);
+	}
+	fsnotify_group_unlock(group);
+
+clear:
+	while (1) {
+		fsnotify_group_lock(group);
+		if (list_empty(head)) {
+			fsnotify_group_unlock(group);
+			break;
+		}
+		mark = list_first_entry(head, struct fsnotify_mark, g_list);
+		fsnotify_get_mark(mark);
+		fsnotify_detach_mark(mark);
+		fsnotify_group_unlock(group);
+		fsnotify_free_mark(mark);
+		fsnotify_put_mark(mark);
+	}
+}
+
+/* Destroy all marks attached to an object via connector */
+void fsnotify_destroy_marks(fsnotify_connp_t *connp)
+{
+	struct fsnotify_mark_connector *conn;
+	struct fsnotify_mark *mark, *old_mark = NULL;
+	void *objp;
+	unsigned int type;
+
+	conn = fsnotify_grab_connector(connp);
+	if (!conn)
+		return;
+	/*
+	 * We have to be careful since we can race with e.g.
+	 * fsnotify_clear_marks_by_group() and once we drop the conn->lock, the
+	 * list can get modified. However we are holding mark reference and
+	 * thus our mark cannot be removed from obj_list so we can continue
+	 * iteration after regaining conn->lock.
+	 */
+	hlist_for_each_entry(mark, &conn->list, obj_list) {
+		fsnotify_get_mark(mark);
+		spin_unlock(&conn->lock);
+		if (old_mark)
+			fsnotify_put_mark(old_mark);
+		old_mark = mark;
+		fsnotify_destroy_mark(mark, mark->group);
+		spin_lock(&conn->lock);
+	}
+	/*
+	 * Detach list from object now so that we don't pin inode until all
+	 * mark references get dropped. It would lead to strange results such
+	 * as delaying inode deletion or blocking unmount.
+	 */
+	objp = fsnotify_detach_connector_from_object(conn, &type);
+	spin_unlock(&conn->lock);
+	if (old_mark)
+		fsnotify_put_mark(old_mark);
+	fsnotify_drop_object(type, objp);
+}
+
+/*
+ * Nothing fancy, just initialize lists and locks and counters.
+ */
+void fsnotify_init_mark(struct fsnotify_mark *mark,
+			struct fsnotify_group *group)
+{
+	memset(mark, 0, sizeof(*mark));
+	spin_lock_init(&mark->lock);
+	refcount_set(&mark->refcnt, 1);
+	fsnotify_get_group(group);
+	mark->group = group;
+	WRITE_ONCE(mark->connector, NULL);
+}
+EXPORT_SYMBOL_GPL(fsnotify_init_mark);
+
+/*
+ * Destroy all marks in destroy_list, waits for SRCU period to finish before
+ * actually freeing marks.
+ */
+static void fsnotify_mark_destroy_workfn(struct work_struct *work)
+{
+	struct fsnotify_mark *mark, *next;
+	struct list_head private_destroy_list;
+
+	spin_lock(&destroy_lock);
+	/* exchange the list head */
+	list_replace_init(&destroy_list, &private_destroy_list);
+	spin_unlock(&destroy_lock);
+
+	synchronize_srcu(&fsnotify_mark_srcu);
+
+	list_for_each_entry_safe(mark, next, &private_destroy_list, g_list) {
+		list_del_init(&mark->g_list);
+		fsnotify_final_mark_destroy(mark);
+	}
+}
+
+/* Wait for all marks queued for destruction to be actually destroyed */
+void fsnotify_wait_marks_destroyed(void)
+{
+	flush_delayed_work(&reaper_work);
+}
+EXPORT_SYMBOL_GPL(fsnotify_wait_marks_destroyed);