On Thu, Mar 02, 2006 at 01:29:50PM -0800, Chen, Kenneth W wrote: > Hugh Dickins wrote on Thursday, March 02, 2006 12:27 PM > > But the first part, || instead of && in is_hugepage_only_range, looks > > insufficient: the start and end of the range might each fall in a > > non-huge region, but the range still cross a huge region. > > > > Ah, does RGN_HPAGE nestle up against the TASK_SIZE roof, so any range > > already tested against TASK_SIZE (as get_unmapped_area has) cannot > > cross RGN_HPAGE? If so, perhaps it deserves a comment there. And > > if that is so, and can be relied upon, is_hugepage_only_range need > > only be testing REGION_NUMBER(addr+len-1) - but it does seem fragile. > > There are many address range check before we hit get_unmapped area. > ia64 can never have a vma range that crosses region boundary. David > pointed out earlier that shmat and mremap can still slip through the > crack and he has a patch that fixed it. But yes, this patch is making > that assumption (or relying on checks being done properly beforehand). In fact with that other patch, which ensures that no region-crossing ranges get through, simply (REGION_NUMBER(addr) == RGN_HPAGE) would be sufficient; either both start and end are in the hugepage region, or they're both in the same different region. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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