On 07/29/2013 11:49 PM, Xishi Qiu wrote: > I think we can remove "BUG_ON(start_pfn >= end_pfn)" in __offline_pages(), > because in memory_block_action() "nr_pages = PAGES_PER_SECTION * sections_per_block" > is always greater than 0. ... > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1472,7 +1472,6 @@ static int __ref __offline_pages(unsigned long start_pfn, > struct zone *zone; > struct memory_notify arg; > > - BUG_ON(start_pfn >= end_pfn); > /* at least, alignment against pageblock is necessary */ > if (!IS_ALIGNED(start_pfn, pageblock_nr_pages)) > return -EINVAL; I think you're saying that you don't see a way to hit this BUG_ON() in practice. That does appear to be true, unless sections_per_block ended up 0 or negative. The odds of getting in to this code if 'sections_per_block' was bogus are pretty small. Or, is this a theoretical thing that folks might run in to when adding new features or developing? It's in a cold path and the cost of the check is miniscule. The original author (cc'd) also saw a need to put this in probably because he actually ran in to this. In any case, it looks fairly safe to me: Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> -- 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>