ftrace: fix incorrect hash size in register_ftrace_direct()

JIRA: https://issues.redhat.com/browse/RHEL-115358

commit 92f1d3b
Author: Menglong Dong <menglong8.dong@gmail.com>
Date:   Sun Apr 13 09:44:44 2025 +0800

    ftrace: fix incorrect hash size in register_ftrace_direct()

    The maximum of the ftrace hash bits is made fls(32) in
    register_ftrace_direct(), which seems illogical. So, we fix it by making
    the max hash bits FTRACE_HASH_MAX_BITS instead.

    Link: https://lore.kernel.org/20250413014444.36724-1-dongml2@chinatelecom.cn
    Fixes: d05cb47 ("ftrace: Fix modification of direct_function hash while in use")
    Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
    Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
    Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

kernel/trace/ftrace.c

@@ -5944,9 +5944,10 @@ int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
 
 	/* Make a copy hash to place the new and the old entries in */
 	size = hash->count + direct_functions->count;
-	if (size > 32)
-		size = 32;
-	new_hash = alloc_ftrace_hash(fls(size));
+	size = fls(size);
+	if (size > FTRACE_HASH_MAX_BITS)
+		size = FTRACE_HASH_MAX_BITS;
+	new_hash = alloc_ftrace_hash(size);
 	if (!new_hash)
 		goto out_unlock;