On 2021/9/13 20:59, Michal Hocko wrote: > On Mon 13-09-21 20:43:35, Miaohe Lin wrote: >> On 2021/9/13 20:20, David Hildenbrand wrote: >>> On 13.09.21 14:12, Michal Hocko wrote: >>>> On Mon 13-09-21 19:51:25, Miaohe Lin wrote: >>>>> In start_isolate_page_range() undo path, pfn_to_online_page() just checks >>>>> the first pfn in a pageblock while __first_valid_page() will traverse the >>>>> pageblock until the first online pfn is found. So we may miss the call to >>>>> unset_migratetype_isolate() in undo path and pages will remain isolated >>>>> unexpectedly. Fix this by calling undo_isolate_page_range() and this will >>>>> also help to simplify the code further. >>>> >>>> I like the clean up part but is this a real problem that requires CC >>>> stable? Have you ever seen this to be a real problem? It looks like >>>> something based on reading the code. >> >> I'm sorry but I haven't seen this to be a real problem. It's a theoretical bug. > > Make it clear in the changelog Will do. > >>> We discussed that it isn't an issue anymore (we never call it on >>> memory holes), but might have been an issue on older kernels, back >>> when we didn't have the "memory holes" check in the memory offlining >>> path in place. >> >> So is the Cc:stable needed in this case? > > I do not think so. Even if this was happening in the practice then the > practical consequences would be pretty minor, right? (few pageblocks > stay isolated thus unavailable). > > I do realize that the stable tree is in a hoarding mode for quite some > years but my general approach has been (in line with the documentation) > to mark and backport only fixes that really do matter. So even the Fixes tag should be removed ? Many thanks. >
