Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes:
> On Tue, Mar 03, 2020 at 08:45:23PM +1100, Michael Ellerman wrote:
>> Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes:
>> > On Tue, Mar 03, 2020 at 06:46:23PM +1100, Michael Ellerman wrote:
>> >> Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> writes:
>> >> > When calling debugfs functions, there is no need to ever check the
>> >> > return value. The function can work or not, but the code logic should
>> >> > never do something different based on this.
>> >>
>> >> Except it does need to do something different, if the file was created
>> >> it needs to be removed in the remove path.
>> >>
>> >> > diff --git a/arch/powerpc/kvm/timing.c b/arch/powerpc/kvm/timing.c
>> >> > index bfe4f106cffc..8e4791c6f2af 100644
>> >> > --- a/arch/powerpc/kvm/timing.c
>> >> > +++ b/arch/powerpc/kvm/timing.c
>> >> > @@ -207,19 +207,12 @@ static const struct file_operations kvmppc_exit_timing_fops = {
>> >> > void kvmppc_create_vcpu_debugfs(struct kvm_vcpu *vcpu, unsigned int id)
>> >> > {
>> >> > static char dbg_fname[50];
>> >> > - struct dentry *debugfs_file;
>> >> >
>> >> > snprintf(dbg_fname, sizeof(dbg_fname), "vm%u_vcpu%u_timing",
>> >> > current->pid, id);
>> >> > - debugfs_file = debugfs_create_file(dbg_fname, 0666,
>> >> > - kvm_debugfs_dir, vcpu,
>> >> > - &kvmppc_exit_timing_fops);
>> >> > -
>> >> > - if (!debugfs_file) {
>> >> > - printk(KERN_ERR"%s: error creating debugfs file %s\n",
>> >> > - __func__, dbg_fname);
>> >> > - return;
>> >> > - }
>> >> > + debugfs_create_file(dbg_fname, 0666, kvm_debugfs_dir, vcpu,
>> >> > + &kvmppc_exit_timing_fops);
>> >> > +
>> >> >
>> >> > vcpu->arch.debugfs_exit_timing = debugfs_file;
>> >
>> > Ugh, you are right, how did I miss that? How is 0-day missing this?
>> > It's been in my tree for a long time, odd.
>>
>> This code isn't enabled by default, or in any defconfig. So it's only
>> allmodconfig that would trip it, I guess 0-day isn't doing powerpc
>> allmodconfig builds.
>>
>> >> I squashed this in, which seems to work:
>> ...
>> >>
>> >> void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu)
>> >> {
>> >> - if (vcpu->arch.debugfs_exit_timing) {
>> >> + if (!IS_ERR_OR_NULL(vcpu->arch.debugfs_exit_timing)) {
>> >> debugfs_remove(vcpu->arch.debugfs_exit_timing);
>> >> vcpu->arch.debugfs_exit_timing = NULL;
>> >> }
>> >
>> > No, this can just be:
>> > debugfs_remove(vcpu->arch.debugfs_exit_timing);
>> >
>> > No need to check anything, just call it and the debugfs code can handle
>> > it just fine.
>>
>> Oh duh, of course, I should have checked.
>>
>> I'd still like to NULL out the debugfs_exit_timing member, so I'll do:
>>
>> void kvmppc_remove_vcpu_debugfs(struct kvm_vcpu *vcpu)
>> {
>> debugfs_remove(vcpu->arch.debugfs_exit_timing);
>> vcpu->arch.debugfs_exit_timing = NULL;
>> }
>
> Fair enough, but I doubt it ever matters :)
Yeah, but I'm paranoid and I have no way to test this code :)
> Thanks for the fixups, sorry for sending a broken patch, my fault.
No worries, we have too many CONFIG options.
cheers
