On Mon, 2016-09-26 at 10:46 +0200, Michal Hocko wrote: > On Fri 23-09-16 17:53:51, Oleg Nesterov wrote: > > On 09/23, Michal Hocko wrote: > > > > > > On Fri 23-09-16 15:56:36, Oleg Nesterov wrote: > > > > > > > > I think we can simplify this patch. And imo make it better. How about > > > > > > it is certainly less subtle because it doesn't report "sub-vmas". > > > > > > > if (last_addr) { > > > > vma = find_vma(mm, last_addr - 1); > > > > if (vma && vma->vm_start <= last_addr) > > > > vma = m_next_vma(priv, vma); > > > > if (vma) > > > > return vma; > > > > } > > > > > > we would still miss a VMA if the last one got shrunk/split > > > > Not sure I understand what you mean... If the last one was split > > we probably should not report the new vma. > > Right, VMA split is less of a problem. I meant to say that if the > last_vma->vm_end got lower for whatever reason then we could miss a VMA > right after. We actually might want to display such a VMA because it > could be a completely new one. We just do not know whether it is a > former split with enlarged VMA or a completely new one > > [ old VMA ] Hole [ VMA ] > [ old VMA ][ New VMa ] [ VMA ] This is indeed possible. But I see this is like the last_vma enlargement case. I suggest we accept such missing, as we accept the enlargement part of last_vma is not printed. How about we set such target: 1) no duplicate print; 2) no old vma missing (unless it's unmapped); 3) monotonic printing. We accept those newly added/changed parts between 2 partial reads is not printed. How about above suggestion? If you, Dave, Oleg and others accept it, then Oleg's improvement can achieve it, I think. > > > Nevermind, in any case yes, sure, this can't "fix" other corner cases. > > Agreed, or at least I do not see an easy way for that. -- 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>