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charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 30 Mar 2022, at 17:25, Zi Yan wrote: > On 30 Mar 2022, at 16:53, Steven Rostedt wrote: > >> On Wed, 30 Mar 2022 16:29:28 -0400 >> Zi Yan wrote: >> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index bdc8f60ae462..83a90e2973b7 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -1108,6 +1108,8 @@ static inline void __free_one_page(struct page = *page, >>> >>> buddy_pfn =3D __find_buddy_pfn(pfn, order); >>> buddy =3D page + (buddy_pfn - pfn); >>> + if (!page_is_buddy(page, buddy, order)) >>> + goto done_merging; >>> buddy_mt =3D get_pageblock_migratetype(buddy); >>> >>> if (migratetype !=3D buddy_mt >>> >> >> The above did not apply to Linus's tree, nor even the problem commit >> (before or after), but I found where the code is, and added it manuall= y. >> >> It does appear to allow the machine to boot. >> > I just pulled Linus=E2=80=99s tree and grabbed the diff. Anyway, thanks= =2E > > I would like to get more understanding of the issue before blindly send= ing > this as a fix. > > Merge the other thread: >> >> Not sure if this matters or not, but my kernel command line has: >> >> crashkernel=3D256M >> >> Could that have caused this to break? > > Unlikely, 256MB is MAX_ORDER_NR_PAGES aligned (MAX_ORDER is 11 here). > __find_buddy_pfn() will not get any buddy_pfn from crashkernel memory > region, since that would cross MAX_ORDER_NR_PAGES boundary. > > page_is_buddy() checks page_is_guard(buddy), PageBuddy(buddy), > buddy_order(buddy), and page_zone_id(buddy), where page_is_guard(buddy)= > is always false since CONFIG_DEBUG_PAGEALLOC is not set in your config.= > So either PageBuddy(buddy) is false, buddy_order(buddy) !=3D order, > or page_zone_id(buddy) is not the same as page_zone_id(page). > > Do you mind adding the following code right before my fix code above > and provide a complete boot log? I would like to understand what > went wrong. Thanks. > > pr_info("buddy_pfn: %lx, PageBuddy: %d, buddy_order: %d (vs %d), page_z= one_id: %d (vs %d)\n", > buddy_pfn, PageBuddy(buddy), buddy_order(buddy), order, page_zo= ne_id(buddy), > page_zone_id(page)); > > This seems to be a bug in the original code too. But "if (unlikely(has_isolate_pageblock(zone)))" is too rare to trigger i= t. I do not see how having isolated pageblocks in a zone could get us away from checking page_is_buddy(). -- Best Regards, Yan, Zi --=_MailMate_3164F1AF-856D-4B25-BF74-6C87D860CE21_= Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQJDBAEBCgAtFiEE6rR4j8RuQ2XmaZol4n+egRQHKFQFAmJEzukPHHppeUBudmlk aWEuY29tAAoJEOJ/noEUByhU5mEQAJLaGIxob8+0Qg+kpWEl6Q/GkZeo4MuILSlU UZCiAsde8whU5xJOWo5GY14V31mL9oTQ/AKM4KFH6/FWlYJgg5qsj0vrzvy/6xhb 30/KNfg8Jmj8gY2aLb+fpvONOiMaKM0m4tbIMCmk77o1HhnbsGIBwx27mUclKfU4 pQtehSYHplOLhDVZfakuChYyG4BqhRf7D6TN9XH7z+zBuTSEPL6mFABT/v4KeCU0 TD870aC43E45N9mMTjac3Ue7J6b/9QnDhJsB1PIv9DyWbJZxuoCSi2IOew+9sP9Y 5+5YY/Iip0WNket/BnD0FayolvO4wrbVhcKmwrYla5U2VO1bV5RI/ZBRCaJtEwKY sPC7kwZv3D3/dMb38iMFsiEHkreUeJmbuOkrCt7k8HhWPOGYwAi2sTt/A4+liN+9 59tKBE1QdcK2nG/pPpbyYcyxV5Fwbx0z11Dg99jkCaWTdAFu3Zm4193F7AHfm+vg nsZa9vsjcoP65pg/HaHyOBjP89VXV63aD5vUGuDyLW3vjn3bTqWM9U7bXdTcOIdd EwaBTVMaDklNzH+ZsT14NmYaq0L9U6VsfLgdvZ+kSt01Tetp5bha7ye5gXWxrtL3 QrB/VCi3k9XXV66CEr0bYiQs+Pf57fjD5S/IsGqLs5OkI7IPkde0/gnljwdd0qB1 Qd1DZRNt =lWlU -----END PGP SIGNATURE----- --=_MailMate_3164F1AF-856D-4B25-BF74-6C87D860CE21_=--