>On Tue, 1 Mar 2016 06:14:32 +0000 Atsushi Kumagai <ats-kumagai at wm.jp.nec.com> wrote: > >> makedumpfile refers page.lru.next to get the order of compound pages >> for page filtering. However, now the order is stored in page.compound_order, >> hence VMCOREINFO should be updated to export the offset of >> page.compound_order. >> >> The fact is, page.compound_order was introduced already in kernel 4.0, >> but the offset of it was the same as page.lru.next until kernel 4.3, >> so this was not actual problem. >> >> The above can be said also for page.lru.prev and page.compound_dtor, >> it's necessary to detect hugetlbfs pages. Further, the content was >> changed from direct address to the ID which means dtor. > >It's unclear which kernels need the patch and why. I *think* that the >patch is needed in 4.3.x, 4.4.x, 4.5.x and 4.6 in order to make >makedumpfile work correctly. Is that right? The patch is necessary for 4.4.x, 4.5.x and 4.6. 4.3.x don't have the problem. >And it appears that [patch 2/2] is needed in 4.0+? [patch 2/2] is for 4.5.x and latter: $ git name-rev 1c290f642101e6 1c290f642101e6 tags/v4.5-rc1~77^2~129 $ >However in both cases I am uncertain - what are the end-user visible >effects of these regressions? Why can bugs remain in place for so long >without having been observed? The problem is that unnecessary hugepages wouldn't be removed from a dump file in the older kernels. This means that extra disk space would be consumed. It's a problem, but not critical. >Please make all these things clear when perparing changelogs for >bugfixes: which kernel versions need fixing and why (ie: what are the >end-user visible effects of the bug). Sure, I will be careful about it. Thanks, Atsushi Kumagai