On 29/08/2017 14:04, Peter Zijlstra wrote: > On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote: >> On 27/08/2017 02:18, Kirill A. Shutemov wrote: >>>> + >>>> + if (unlikely(!vma->anon_vma)) >>>> + goto unlock; >>> >>> It deserves a comment. >> >> You're right I'll add it in the next version. >> For the record, the root cause is that __anon_vma_prepare() requires the >> mmap_sem to be held because vm_next and vm_prev must be safe. > > But should that test not be: > > if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) > goto unlock; > > Because !anon vmas will never have ->anon_vma set and you don't want to > exclude those.
Yes in the case we later allow non anonymous vmas to be handled. Currently only anonymous vmas are supported so the check is good enough, isn't it ?
