> -----Original Message----- > From: Miaohe Lin <linmiaohe@xxxxxxxxxx> > Sent: Friday, August 12, 2022 14:41 > 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 2022/8/12 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). > I try a quick fix, and cc'ed you. Ugly design, but your fix is kept. > Thanks, > Miaohe Lin
