FYI, we noticed the following commit: https://github.com/goldwynr/linux kobjectify-fs commit dfac59d60d602849663e045af372ce9222d7672e ("Add kset to file_system_type") on test machine: vm-kbuild-1G: 2 threads qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap with 1G memory caused below changes: [ 0.332120] Mount-cache hash table entries: 2048 (order: 2, 16384 bytes) [ 0.334294] Mountpoint-cache hash table entries: 2048 (order: 2, 16384 bytes) [ 0.336683] ------------[ cut here ]------------ [ 0.338551] WARNING: CPU: 0 PID: 0 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x64/0x80 [ 0.341857] sysfs: cannot create duplicate filename '/fs/cgroup' [ 0.343838] Modules linked in: [ 0.345451] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-00001-gdfac59d #1 [ 0.348441] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014 [ 0.351800] 0000000000000000 ffffffff81e03d68 ffffffff8142e5aa ffffffff81e03db8 [ 0.355385] 0000000000000000 ffffffff81e03da8 ffffffff8107b9a1 0000001f00000073 [ 0.359553] ffff880035823000 ffffffff81cc71bf ffff880035a470f0 0000000000000000 [ 0.363055] Call Trace: [ 0.364358] [<ffffffff8142e5aa>] dump_stack+0x63/0x89 [ 0.367373] [<ffffffff8107b9a1>] __warn+0xd1/0xf0 [ 0.369126] [<ffffffff8107ba0f>] warn_slowpath_fmt+0x4f/0x60 [ 0.371126] [<ffffffff8127a3b4>] sysfs_warn_dup+0x64/0x80 [ 0.373048] [<ffffffff8127a497>] sysfs_create_dir_ns+0x77/0x90 [ 0.374994] [<ffffffff814313a5>] kobject_add_internal+0xb5/0x340 [ 0.377034] [<ffffffff814311be>] ? kobject_set_name+0x3e/0x40 [ 0.379066] [<ffffffff814316f9>] kset_register+0x49/0x70 [ 0.380955] [<ffffffff8143178b>] kset_create_and_add+0x6b/0xa0 [ 0.382880] [<ffffffff81219f27>] register_filesystem+0x97/0xa0 [ 0.384803] [<ffffffff82004661>] cgroup_init+0x356/0x3c9 [ 0.386783] [<ffffffff81fdaf44>] start_kernel+0x3f1/0x436 [ 0.388622] [<ffffffff81fda120>] ? early_idt_handler_array+0x120/0x120 [ 0.390790] [<ffffffff81fda4ec>] x86_64_start_reservations+0x2a/0x2c [ 0.392822] [<ffffffff81fda629>] x86_64_start_kernel+0x13b/0x14a [ 0.394913] ---[ end trace bbb5bd06d9154d79 ]--- [ 0.396643] ------------[ cut here ]------------ FYI, raw QEMU command line is: qemu-system-x86_64 -enable-kvm -cpu Haswell,+smep,+smap -kernel /pkg/linux/x86_64-rhel/gcc-4.9/dfac59d60d602849663e045af372ce9222d7672e/vmlinuz-4.6.0-rc5-00001-gdfac59d -append 'root=/dev/ram0 user=lkp job=/lkp/scheduled/vm-kbuild-1G-10/bisect_boot-1-debian-x86_64-2015-02-07.cgz-x86_64-rhel-dfac59d60d602849663e045af372ce9222d7672e-20160427-91533-idhx15-1.yaml ARCH=x86_64 kconfig=x86_64-rhel branch=linux-devel/devel-catchup-201604262209 commit=dfac59d60d602849663e045af372ce9222d7672e BOOT_IMAGE=/pkg/linux/x86_64-rhel/gcc-4.9/dfac59d60d602849663e045af372ce9222d7672e/vmlinuz-4.6.0-rc5-00001-gdfac59d max_uptime=600 RESULT_ROOT=/result/boot/1/vm-kbuild-1G/debian-x86_64-2015-02-07.cgz/x86_64-rhel/gcc-4.9/dfac59d60d602849663e045af372ce9222d7672e/0 LKP_SERVER=inn earlyprintk=ttyS0,115200 systemd.log_level=err debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 console=ttyS0,115200 console=tty0 vga=normal rw ip=::::vm-kbuild-1G-10::dhcp' -initrd /fs/sde1/initrd-vm-kbuild-1G-10 -m 1024 -smp 2 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::23009-:22 -boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -device virtio-scsi-pci,id=scsi0 -drive file=/fs/sde1/disk0-vm-kbuild-1G-10,if=none,id=hd0,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd0,scsi-id=1,lun=0 -drive file=/fs/sde1/disk1-vm-kbuild-1G-10,if=none,id=hd1,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd1,scsi-id=1,lun=1 -drive file=/fs/sde1/disk2-vm-kbuild-1G-10,if=none,id=hd2,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd2,scsi-id=1,lun=2 -drive file=/fs/sde1/disk3-vm-kbuild-1G-10,if=none,id=hd3,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd3,scsi-id=1,lun=3 -drive file=/fs/sde1/disk4-vm-kbuild-1G-10,if=none,id=hd4,media=disk,aio=native,cache=none -device scsi-hd,bus=scsi0.0,drive=hd4,scsi-id=1,lun=4 -pidfile /dev/shm/kboot/pid-vm-kbuild-1G-10 -serial file:/dev/shm/kboot/serial-vm-kbuild-1G-10 -daemonize -display none -monitor null Thanks, Xiaolong