> -----Original Message----- > From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Sent: Wednesday, August 17, 2022 08:59 > To: Wang, Haiyue <haiyue.wang@xxxxxxxxx> > Cc: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; david@xxxxxxxxxx; apopple@xxxxxxxxxx; > linmiaohe@xxxxxxxxxx; Huang, Ying <ying.huang@xxxxxxxxx>; songmuchun@xxxxxxxxxxxxx; > naoya.horiguchi@xxxxxxxxx; alex.sierra@xxxxxxx; Heiko Carstens <hca@xxxxxxxxxxxxx>; Vasily Gorbik > <gor@xxxxxxxxxxxxx>; Alexander Gordeev <agordeev@xxxxxxxxxxxxx>; Christian Borntraeger > <borntraeger@xxxxxxxxxxxxx>; Sven Schnelle <svens@xxxxxxxxxxxxx>; Mike Kravetz > <mike.kravetz@xxxxxxxxxx> > Subject: Re: [PATCH v6 1/2] mm: migration: fix the FOLL_GET failure on following huge page > > On Tue, 16 Aug 2022 10:21:00 +0800 Haiyue Wang <haiyue.wang@xxxxxxxxx> wrote: > > > Not all huge page APIs support FOLL_GET option, so move_pages() syscall > > will fail to get the page node information for some huge pages. > > > > Like x86 on linux 5.19 with 1GB huge page API follow_huge_pud(), it will > > return NULL page for FOLL_GET when calling move_pages() syscall with the > > NULL 'nodes' parameter, the 'status' parameter has '-2' error in array. > > > > Note: follow_huge_pud() now supports FOLL_GET in linux 6.0. > > Link: https://lore.kernel.org/all/20220714042420.1847125-3-naoya.horiguchi@xxxxxxxxx > > > > But these huge page APIs don't support FOLL_GET: > > 1. follow_huge_pud() in arch/s390/mm/hugetlbpage.c > > Let's tell the s390 maintainers. > > > 2. follow_huge_addr() in arch/ia64/mm/hugetlbpage.c > > It will cause WARN_ON_ONCE for FOLL_GET. > > ia64 doesn't have maintainers :( Can we come up with something local to > arch/ia64 for this? The 'follow_huge_addr' itself just has interest on "FOLL_WRITE" struct page * follow_huge_addr(struct mm_struct *mm, unsigned long address, int write) And arch/ia64 defines this function 17 years ago ... But I found that "WARN_ON_ONCE for FOLL_GET" was introduced on 2005-10-29 by commit: [PATCH] mm: follow_page with inner ptlock https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=deceb6cd17e6dfafe4c4f81b1b4153bc41b2cb70 - page = follow_huge_addr(mm, address, write); - if (! IS_ERR(page)) - return page; + page = follow_huge_addr(mm, address, flags & FOLL_WRITE); + if (!IS_ERR(page)) { + BUG_ON(flags & FOLL_GET); + goto out; + } > > > 3. follow_huge_pgd() in mm/hugetlb.c > > Hi, Mike. > > > } > > I would be better to fix this for real at those three client code sites? Then 5.19 will break for a while to wait for the final BIG patch ?
