dcache: Replace simple_strtoul with kstrtoul in set_dhash_entries

Replace simple_strtoul() with the recommended kstrtoul() for parsing the
'dhash_entries=' boot parameter.

Check the return value of kstrtoul() and reject invalid values. This
adds error handling while preserving behavior for existing values, and
removes use of the deprecated simple_strtoul() helper.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20251216145236.44520-2-thorsten.blum@linux.dev
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: toblux

fs/dcache.c

@@ -3227,10 +3227,7 @@ EXPORT_SYMBOL(d_parent_ino);
 static __initdata unsigned long dhash_entries;
 static int __init set_dhash_entries(char *str)
 {
-	if (!str)
-		return 0;
-	dhash_entries = simple_strtoul(str, &str, 0);
-	return 1;
+	return kstrtoul(str, 0, &dhash_entries) == 0;
 }
 __setup("dhash_entries=", set_dhash_entries);