eventfs: Use list_add_tail_rcu() for SRCU-protected children list

Commit d260327 ("eventfs: Use list_del_rcu() for SRCU protected
list variable") converted the removal side to pair with the
list_for_each_entry_srcu() walker in eventfs_iterate(). The insertion
in eventfs_create_dir() was left as a plain list_add_tail(), which on
weakly-ordered architectures can expose a new entry to the SRCU reader
before its list pointers and fields are observable.

Use list_add_tail_rcu() so the publication pairs with the existing
list_del_rcu() and list_for_each_entry_srcu().

Fixes: 43aa6f9 ("eventfs: Get rid of dentry pointers without refcounts")
Cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: David Carlier <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>

Author: devnexen

fs/tracefs/event_inode.c

@@ -706,7 +706,7 @@ struct eventfs_inode *eventfs_create_dir(const char *name, struct eventfs_inode
 
 	scoped_guard(mutex, &eventfs_mutex) {
 		if (!parent->is_freed)
-			list_add_tail(&ei->list, &parent->children);
+			list_add_tail_rcu(&ei->list, &parent->children);
 	}
 	/* Was the parent freed? */
 	if (list_empty(&ei->list)) {