On 19.04.2018 09:33, Michal Hocko wrote: > On Wed 18-04-18 17:46:25, David Hildenbrand wrote: > [...] >> BTW I was able to easily produce the case where do_migrate_range() would >> loop for ever (well at least for multiple minutes, but I assume this >> would have went on :) ) > > I am definitely interested to hear details. > migrate_pages() seems to be returning > 0 all the time. Seems to come from too many -EAGAIN from unmap_and_move(). This in return (did not go further down that road) can be as simple as trylock_page() failing. Of course, we could have other permanent errors here (-ENOMEM). __offline_pages() ignores all errors coming from do_migrate_range(). So in theory, this can take forever - at least not what I want for my use case. I want it to fail fast. "if this block cannot be offlined, try another one". I wonder if it is the right thing to do in __offline_pages() to ignore even permanent errors. Anyhow, I think I'll need some way of telling offline_pages "please don't retry forever". -- Thanks, David / dhildenb
