When inode is being inserted into inode cache, lookup whether there are
some notification marks for this inode and reconnect them to it.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/inode.c                       |  1 +
 fs/notify/mark.c                 | 37 ++++++++++++++++++++++++++++++++
 include/linux/fsnotify_backend.h | 13 +++++++++++
 3 files changed, 51 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index 01ebdc40021e..9f9507eea645 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1450,6 +1450,7 @@ struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 			spin_unlock(&inode->i_lock);
 			spin_unlock(&inode_hash_lock);
 			inode_sb_list_add(inode);
+			fsnotify_generic_reconnect_inode_marks(inode);
 
 			/* Return the locked inode with I_NEW set, the
 			 * caller is responsible for filling in the contents
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index f6a197c63c1d..8fe7128f4122 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -731,6 +731,43 @@ fsnotify_alloc_inode_connector(struct inode *inode)
 	return &iconn->common;
 }
 
+/*
+ * If there are existing notification marks for the inode, attach them
+ * to it.
+ */
+void fsnotify_reconnect_inode_marks(struct inode *inode, void *key)
+{
+	struct fsnotify_sb_info *info = fsnotify_sb_info(inode->i_sb);
+	const struct rhashtable_params *params =
+			fsnotify_get_conn_hash_params(inode->i_sb);
+	struct fsnotify_inode_mark_connector *iconn;
+	struct fsnotify_mark_connector *conn;
+	int idx;
+
+	if (!info)
+		return;
+
+	idx = srcu_read_lock(&fsnotify_mark_srcu);
+	iconn = rhashtable_lookup_fast(&info->inode_conn_hash, key, *params);
+	if (!iconn)
+		goto out_srcu;
+	conn = &iconn->common;
+	spin_lock(&conn->lock);
+	/* The connector is just undergoing destruction? */
+	if (hlist_empty(&conn->list))
+		goto out_lock;
+	conn->type = FSNOTIFY_OBJ_TYPE_INODE;
+	conn->obj = inode;
+	rcu_assign_pointer(inode->i_fsnotify_marks, conn);
+	__fsnotify_recalc_mask(conn);
+	fsnotify_update_sb_watchers(conn);
+out_lock:
+	spin_unlock(&conn->lock);
+out_srcu:
+	srcu_read_unlock(&fsnotify_mark_srcu, idx);
+}
+EXPORT_SYMBOL(fsnotify_reconnect_inode_marks);
+
 static void fsnotify_unhash_connector(struct fsnotify_mark_connector *conn)
 {
 	if (!(conn->flags & FSNOTIFY_CONN_FLAG_HASHED))
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index bf6796be7561..267c6587af97 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -921,6 +921,13 @@ static inline void fsnotify_init_event(struct fsnotify_event *event)
 int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
 			 size_t count);
 
+void fsnotify_reconnect_inode_marks(struct inode *inode, void *key);
+/* Reconnection function for filesystems using fsnotify_inode_mark_connector */
+static inline void fsnotify_generic_reconnect_inode_marks(struct inode *inode)
+{
+	fsnotify_reconnect_inode_marks(inode, &inode->i_ino);
+}
+
 #else
 
 static inline int fsnotify_pre_content(const struct path *path,
@@ -971,6 +978,12 @@ static inline void fsnotify_unmount_inodes(struct super_block *sb)
 static inline void fsnotify_mnt(__u32 mask, struct mnt_namespace *ns, struct vfsmount *mnt)
 {}
 
+static inline void fsnotify_reconnect_inode_marks(struct inode *inode, void *key)
+{}
+
+static inline void fsnotify_generic_reconnect_inode_marks(struct inode *inode)
+{}
+
 #endif	/* CONFIG_FSNOTIFY */
 
 #endif	/* __KERNEL __ */
-- 
2.51.0