On Fri, Oct 28, 2022 at 2:44 PM Zach O'Keefe <zokeefe@xxxxxxxxxx> wrote: > > On Oct 28 10:37, Yang Shi wrote: > > On Fri, Oct 28, 2022 at 12:49 AM syzbot > > <syzbot+0044b22d177870ee974f@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > Hello, > > > > > > syzbot found the following issue on: > > > > > > HEAD commit: a70385240892 Merge tag 'perf_urgent_for_v6.1_rc2' of git:/.. > > > git tree: upstream > > > console+strace: https://syzkaller.appspot.com/x/log.txt?x=13f4726a880000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=ea03ca45176080bc > > > dashboard link: https://syzkaller.appspot.com/bug?extid=0044b22d177870ee974f > > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13726f72880000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13b57436880000 > > > > > > Downloadable assets: > > > disk image: https://storage.googleapis.com/syzbot-assets/5e17f1e83cf3/disk-a7038524.raw.xz > > > vmlinux: https://storage.googleapis.com/syzbot-assets/f8ef729877f7/vmlinux-a7038524.xz > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > Reported-by: syzbot+0044b22d177870ee974f@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > > > ------------[ cut here ]------------ > > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 __alloc_pages_node include/linux/gfp.h:221 [inline] > > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > > > WARNING: CPU: 1 PID: 3646 at include/linux/gfp.h:221 alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > > > > It looks like the node requested by the allocation is offlined, and > > the allocation is using __GFP_THISNODE. It doesn't sound like > > khugepaged specific problem IIUC, I don't see other callsites do > > anything to prevent the node from being offlined. > > > > Shall we remove that warn? The page allocation call will return NULL > > anyway. Or we could just ignore the warn? > > > > Thanks for taking a look, Yang. > > As for the warn -- I don't see the value in the warning at present. As you > mention, I don't think it's a khugepaged-thing (as, at least from skimming, > other callsites don't take care to expect that the node is online). The > allocation might fail -- for a number of reasons -- and I don't think > __GFP_THISNODE + offline node is so special to deserve a warn. > > A different question, is if this particular callsite wants to defend against > that possibility. My understanding, which I state without data, is that the > performance of accessing remote memory outweighs the benefit of pmd-mapping the > memory -- and so I think we rightly fail here. > > So, my vote is to just remove the warn. Thanks, Zach. Did some archeology, it seems the warning was even stronger before commit 8addc2d00fe17 ("mm: do not warn on offline nodes unless the specific node is explicitly requested"). That commit softened the warning for __GFP_THISNODE. This warning seems not quite useful TBH because: * There is no guarantee the node is online for __GFP_THISNODE context * Kernel just fails the allocation regardless the warning, and it looks all callsites handle the allocation failure gracefully. So I think we'd better remove this warning. > > Thanks, > Zach > > > > Modules linked in: > > > CPU: 1 PID: 3646 Comm: syz-executor210 Not tainted 6.1.0-rc1-syzkaller-00454-ga70385240892 #0 > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 > > > RIP: 0010:__alloc_pages_node include/linux/gfp.h:221 [inline] > > > RIP: 0010:hpage_collapse_alloc_page mm/khugepaged.c:807 [inline] > > > RIP: 0010:alloc_charge_hpage+0x802/0xaa0 mm/khugepaged.c:963 > > > Code: e5 01 4c 89 ee e8 6e f9 ae ff 4d 85 ed 0f 84 28 fc ff ff e8 70 fc ae ff 48 8d 6b ff 4c 8d 63 07 e9 16 fc ff ff e8 5e fc ae ff <0f> 0b e9 96 fa ff ff 41 bc 1a 00 00 00 e9 86 fd ff ff e8 47 fc ae > > > RSP: 0018:ffffc90003fdf7d8 EFLAGS: 00010293 > > > RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 > > > RDX: ffff888077f457c0 RSI: ffffffff81cd8f42 RDI: 0000000000000001 > > > RBP: ffff888079388c0c R08: 0000000000000001 R09: 0000000000000000 > > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 > > > R13: dffffc0000000000 R14: 0000000000000000 R15: 0000000000000000 > > > FS: 00007f6b48ccf700(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000 > > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > CR2: 00007f6b48a819f0 CR3: 00000000171e7000 CR4: 00000000003506e0 > > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > > Call Trace: > > > <TASK> > > > collapse_file+0x1ca/0x5780 mm/khugepaged.c:1715 > > > hpage_collapse_scan_file+0xd6c/0x17a0 mm/khugepaged.c:2156 > > > madvise_collapse+0x53a/0xb40 mm/khugepaged.c:2611 > > > madvise_vma_behavior+0xd0a/0x1cc0 mm/madvise.c:1066 > > > madvise_walk_vmas+0x1c7/0x2b0 mm/madvise.c:1240 > > > do_madvise.part.0+0x24a/0x340 mm/madvise.c:1419 > > > do_madvise mm/madvise.c:1432 [inline] > > > __do_sys_madvise mm/madvise.c:1432 [inline] > > > __se_sys_madvise mm/madvise.c:1430 [inline] > > > __x64_sys_madvise+0x113/0x150 mm/madvise.c:1430 > > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > RIP: 0033:0x7f6b48a4eef9 > > > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > > > RSP: 002b:00007f6b48ccf318 EFLAGS: 00000246 ORIG_RAX: 000000000000001c > > > RAX: ffffffffffffffda RBX: 00007f6b48af0048 RCX: 00007f6b48a4eef9 > > > RDX: 0000000000000019 RSI: 0000000000600003 RDI: 0000000020000000 > > > RBP: 00007f6b48af0040 R08: 0000000000000000 R09: 0000000000000000 > > > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f6b48aa53a4 > > > R13: 00007f6b48bffcbf R14: 00007f6b48ccf400 R15: 0000000000022000 > > > </TASK> > > > > > > > > > --- > > > This report is generated by a bot. It may contain errors. > > > See https://goo.gl/tpsmEJ for more information about syzbot. > > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > > > syzbot will keep track of this issue. See: > > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > > syzbot can test patches for this issue, for details see: > > > https://goo.gl/tpsmEJ#testing-patches > > >
