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;
}
cheers
