Messages in this thread | | | From | Atsushi Kumagai <> | Subject | RE: [PATCH 1/2] kexec: update VMCOREINFO for compound_order/dtor | Date | Mon, 4 Apr 2016 01:04:38 +0000 |
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>On Tue, 1 Mar 2016 06:14:32 +0000 Atsushi Kumagai <ats-kumagai@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
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