On Mon 24-09-18 22:10:30, Anshuman Khandual wrote: > > > On 09/24/2018 08:00 PM, Michal Hocko wrote: > > On Mon 24-09-18 19:44:55, Anshuman Khandual wrote: > >> When unmap_and_move[_huge_page] function fails due to lack of memory, the > >> splitting should happen only for transparent huge pages not for HugeTLB > >> pages. PageTransHuge() returns true for both THP and HugeTLB pages. Hence > >> the conditonal check should test PagesHuge() flag to make sure that given > >> pages is not a HugeTLB one. > > > > Well spotted! Have you actually seen this happening or this is review > > driven? I am wondering what would be the real effect of this mismatch? > > I have tried to follow to code path but I suspect > > split_huge_page_to_list would fail for hugetlbfs pages. If there is a > > more serious effect then we should mark the patch for stable as well. > > split_huge_page_to_list() fails on HugeTLB pages. I was experimenting around > moving 32MB contig HugeTLB pages on arm64 (with a debug patch applied) hit > the following stack trace when the kernel crashed. > > [ 3732.462797] Call trace: > [ 3732.462835] split_huge_page_to_list+0x3b0/0x858 > [ 3732.462913] migrate_pages+0x728/0xc20 > [ 3732.462999] soft_offline_page+0x448/0x8b0 > [ 3732.463097] __arm64_sys_madvise+0x724/0x850 > [ 3732.463197] el0_svc_handler+0x74/0x110 > [ 3732.463297] el0_svc+0x8/0xc > [ 3732.463347] Code: d1000400 f90b0e60 f2fbd5a2 a94982a1 (f9000420) Please make sure this makes it to the changelog and mark the patch for stable. -- Michal Hocko SUSE Labs
