Hi In my opinion, pfn_valid() is meant to be able to tell if a given PFN has valid section, and That section can contain corresponding mem_map. but, the section can be has holes, the corresponding mem_map also be allcoated, resulting in treating the PFN as valid incorrect. what's problem for the interpretation of the above? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>