Al Viro <v...@zeniv.linux.org.uk> writes:
> On Mon, Mar 14, 2016 at 08:48:26AM +0800, kernel test robot wrote:
>> FYI, we noticed the below changes on
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git work.lookups
>> commit fda89e65743179d09e55bc6c265d06fa5efa8803 ("namei: untanlge
>> lookup_fast()")
>
> Unfortunately, while with my normal .config it reliably triggers an oops
> in x86_pmu_enable() (with or without those patches), yours triggers nothing
> but a pile of OOMs. How much RAM do you give those suckers? I'm _not_
> testing those on bare hardware, obviously - it's KVM image.
qemu-system-x86_64 -enable-kvm -cpu qemu64,+ssse3 -kernel
/pkg/linux/x86_64-rhel/gcc-4.9/fda89e65743179d09e55bc6c265d06fa5efa8803/vmlinuz-4.5.0-rc4-00017-gfda89e6
-append 'root=/dev/ram0 user=lkp
job=/lkp/scheduled/vm-kbuild-4G-3/bisect_trinity-300s-debian-x86_64-2015-02-07.cgz-x86_64-rhel-fda89e65743179d09e55bc6c265d06fa5efa8803-20160312-104797-ow7uw0-0.yaml
ARCH=x86_64 kconfig=x86_64-rhel branch=linux-devel/devel-catchup-201603120257
commit=fda89e65743179d09e55bc6c265d06fa5efa8803
BOOT_IMAGE=/pkg/linux/x86_64-rhel/gcc-4.9/fda89e65743179d09e55bc6c265d06fa5efa8803/vmlinuz-4.5.0-rc4-00017-gfda89e6
max_uptime=1500
RESULT_ROOT=/result/trinity/300s/vm-kbuild-4G/debian-x86_64-2015-02-07.cgz/x86_64-rhel/gcc-4.9/fda89e65743179d09e55bc6c265d06fa5efa8803/0
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-4G-3::dhcp' -initrd /fs/sdg1/initrd-vm-kbuild-4G-3 -m 4096
-smp 4 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::23034-:22
-boot order=nc -no-reboot -watchdog i6300esb -rtc base=localtime -drive
file=/fs/sdg1/disk0-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk1-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk2-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk3-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk4-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk5-vm-kbuild-4G-3,media=disk,if=virtio -drive
file=/fs/sdg1/disk6-vm-kbuild-4G-3,media=disk,if=virtio -pidfile
/dev/shm/kboot/pid-vm-kbuild-4G-3 -serial
file:/dev/shm/kboot/serial-vm-kbuild-4G-3 -daemonize -display none -monitor
null
This is the qemu command line we used for testing.
Best Regards,
Huang, Ying
> FWIW, see below for hopefully cleaner fix (will fold once I manage to trigger
> the damn thing and verify that fix indeed fixes). It's on top of offending
> commit. Folks, could you please check if it fixes that crap on your setup?
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 7a5f79f..d721821 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1519,6 +1519,7 @@ static int lookup_fast(struct nameidata *nd,
> struct vfsmount *mnt = nd->path.mnt;
> struct dentry *dentry, *parent = nd->path.dentry;
> int err;
> + int status = 1;
>
> /*
> * Rename seqlock is not required here because in the off chance
> @@ -1555,54 +1556,45 @@ static int lookup_fast(struct nameidata *nd,
> return -ECHILD;
>
> *seqp = seq;
> - if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
> - int status = d_revalidate(dentry, nd->flags);
> - if (unlikely(status <= 0)) {
> - if (unlazy_walk(nd, dentry, seq))
> - return -ECHILD;
> - if (status == -ECHILD)
> - status = d_revalidate(dentry,
> nd->flags);
> - if (status <= 0) {
> - if (!status) {
> - d_invalidate(dentry);
> - status = 1;
> - }
> - dput(dentry);
> - return status;
> - }
> - }
> + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
> + status = d_revalidate(dentry, nd->flags);
> + if (unlikely(status <= 0)) {
> + if (unlazy_walk(nd, dentry, seq))
> + return -ECHILD;
> + if (status == -ECHILD)
> + status = d_revalidate(dentry, nd->flags);
> + } else {
> + /*
> + * Note: do negative dentry check after revalidation in
> + * case that drops it.
> + */
> + if (unlikely(negative))
> + return -ENOENT;
> + path->mnt = mnt;
> + path->dentry = dentry;
> + if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
> + return 0;
> + if (unlazy_walk(nd, dentry, seq))
> + return -ECHILD;
> }
> - /*
> - * Note: do negative dentry check after revalidation in
> - * case that drops it.
> - */
> - if (unlikely(negative))
> - return -ENOENT;
> - path->mnt = mnt;
> - path->dentry = dentry;
> - if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
> - return 0;
> - if (unlazy_walk(nd, dentry, seq))
> - return -ECHILD;
> } else {
> dentry = __d_lookup(parent, &nd->last);
> if (unlikely(!dentry))
> return 1;
> - if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
> - int status = d_revalidate(dentry, nd->flags);
> - if (unlikely(status <= 0)) {
> - if (!status) {
> - d_invalidate(dentry);
> - status = 1;
> - }
> - dput(dentry);
> - return status;
> - }
> - }
> - if (unlikely(d_is_negative(dentry))) {
> - dput(dentry);
> - return -ENOENT;
> + if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
> + status = d_revalidate(dentry, nd->flags);
> + }
> + if (unlikely(status <= 0)) {
> + if (!status) {
> + d_invalidate(dentry);
> + status = 1;
> }
> + dput(dentry);
> + return status;
> + }
> + if (unlikely(d_is_negative(dentry))) {
> + dput(dentry);
> + return -ENOENT;
> }
>
> path->mnt = mnt;
> _______________________________________________
> LKP mailing list
> l...@lists.01.org
> https://lists.01.org/mailman/listinfo/lkp
