On Wed, Aug 24, 2011 at 12:13:21AM +0200, Andrea Arcangeli wrote: > Hi Andrew, > > On Tue, Aug 23, 2011 at 02:14:45PM -0700, Andrew Morton wrote: > > > + if ((old_addr & ~HPAGE_PMD_MASK) || > > > + (new_addr & ~HPAGE_PMD_MASK) || > > > + (old_addr + HPAGE_PMD_SIZE) > old_end || > > > > Can (old_addr + HPAGE_PMD_SIZE) wrap past zero? > > Good question. old_addr is hpage aligned so to overflow it'd need to > be exactly at address 0-HPAGE_PMD_SIZE. Can any userland map an > address there? I doubt and surely not x86* or sparc (currently THP is > only enabled on x86 anyway so answer is it can't wrap past zero). But > probably we should add a wrap check for other archs in the future > unless we have a real guarantee from all archs to avoid the check. I > only can guarantee about x86*. I suggest to incorporate this into thp-mremap-support-and-tlb-optimization-fix.patch (it's only for the future but it's zero cost so it's certainly worth it...). Untested... diff --git a/mm/huge_memory.c b/mm/huge_memory.c --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1066,7 +1066,7 @@ int move_huge_pmd(struct vm_area_struct if ((old_addr & ~HPAGE_PMD_MASK) || (new_addr & ~HPAGE_PMD_MASK) || - (old_addr + HPAGE_PMD_SIZE) > old_end || + old_end - old_addr < HPAGE_PMD_SIZE || (new_vma->vm_flags & VM_NOHUGEPAGE)) goto out; -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>