On 2022/8/12 11:04, Wang, Haiyue wrote: >> -----Original Message----- >> From: Miaohe Lin <linmiaohe@xxxxxxxxxx> >> Sent: Friday, August 12, 2022 09:59 >> To: Wang, Haiyue <haiyue.wang@xxxxxxxxx> >> Cc: akpm@xxxxxxxxxxxxxxxxxxxx; Linux-MM <linux-mm@xxxxxxxxx>; linux-kernel <linux- >> kernel@xxxxxxxxxxxxxxx>; Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx>; David Hildenbrand >> <david@xxxxxxxxxx> >> Subject: Re: Linux 5.19 __NR_move_pages failed for hugepage >> >> On 2022/8/11 16:01, Wang, Haiyue wrote: >>> Hi Miaohe, >>> >>> >> >> Hi Haiyue, >> >> Many thanks for your report and debug. >> >>> >>> When I call "*syscall (__NR_move_pages, 0, n_pages, ptr, 0, status, 0)*" to get the huge page node >>> >>> information, it is failed with '-2' returned in 'status' array. >>> >>> >>> >>> After some debug, I found that "*follow_huge_pud*" will return NULL if '*FOLL_GET*' is set. >>> >>> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e66f17ff71772b209eed39de >> 35aaa99ba819c93d >> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e66f17ff71772b209eed39d >> e35aaa99ba819c93d> >>> >>> >>> >>> This will make your patch doesn't work for huge page. >>> >>> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4cd614841c06338a087769ee >> 3cfa96718784d1f5 >> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4cd614841c06338a087769e >> e3cfa96718784d1f5> >>> >> >> Supporting of '*FOLL_GET*' in follow_huge_pud is introduced via the below commit: >> >> https://lore.kernel.org/all/20220714042420.1847125-9- >> naoya.horiguchi@xxxxxxxxx/T/#mb3c83df087fba454b7b4ea32227fb8775ca70081 >> >> But that's still not perfect yet. For s390 version of follow_huge_pud, FOLL_GET is still not supported. >> And pgd level >> hugepage doesn't support FOLL_GET now. >> >>> >>> >>> Not sure you know this issue or not, just share my debug information. >> >> I'm not sure whether it's better to revert my above "problematic" patch first then add it back when >> all hugetlb pages support FOLL_GET. >> Or we could just live with it? Any thoughts? >> > > TBH, the issue is more complicated than I think. :-( > > Looks like only '[PATCH v7 5/8] mm, hwpoison: set PG_hwpoison for busy hugetlb pages' will be > backported to 5.19 ? Only this patch has "Fixes:" tag. If so, it will break 5.19. If you want to mitigate the problem of __NR_move_pages failing for hugepage, "[PATCH v7 2/8] mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry" could be backported to 5.19. > > I just run VPP 'https://fd.io/' to find the error message about huge page allocation > after I switched from 5.18 to 5.19. Do you mean the reported problem is found by VPP? Anyway, you can send a patch to fix the problem if you like. :) I will try fixing it if requested of course (but I'm not sure how to fix it yet). Thanks, Miaohe Lin
