From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
kvm-ppc@vger.kernel.org
Subject: Re: [PATCH 2/6] powerpc: kvm: no need to check return value of debugfs_create functions
Date: Tue, 3 Mar 2020 10:58:49 +0100 [thread overview]
Message-ID: <20200303095849.GA1399072@kroah.com> (raw)
In-Reply-To: <87d09tsrf0.fsf@mpe.ellerman.id.au>
On Tue, Mar 03, 2020 at 08:45:23PM +1100, Michael Ellerman wrote:
> Greg Kroah-Hartman <gregkh@linuxfoundation.org> writes:
> > On Tue, Mar 03, 2020 at 06:46:23PM +1100, Michael Ellerman wrote:
> >> Greg Kroah-Hartman <gregkh@linuxfoundation.org> 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 :)
Thanks for the fixups, sorry for sending a broken patch, my fault.
greg k-h
next prev parent reply other threads:[~2020-03-03 10:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-09 10:58 [PATCH 1/6] powerpc: kernel: no need to check return value of debugfs_create functions Greg Kroah-Hartman
2020-02-09 10:58 ` [PATCH 2/6] powerpc: kvm: " Greg Kroah-Hartman
2020-03-03 7:46 ` Michael Ellerman
2020-03-03 8:50 ` Greg Kroah-Hartman
2020-03-03 9:45 ` Michael Ellerman
2020-03-03 9:58 ` Greg Kroah-Hartman [this message]
2020-03-03 10:32 ` Michael Ellerman
2020-02-09 10:58 ` [PATCH 3/6] powerpc: mm: book3s64: hash_utils: " Greg Kroah-Hartman
2020-02-09 10:58 ` [PATCH 4/6] powerpc: mm: ptdump: " Greg Kroah-Hartman
2020-02-09 10:59 ` [PATCH 5/6] powerpc: cell: axon_msi: " Greg Kroah-Hartman
2020-02-09 10:59 ` [PATCH 6/6] powerpc: powernv: " Greg Kroah-Hartman
2020-02-10 15:01 ` Oliver O'Halloran
2020-02-10 15:19 ` Greg Kroah-Hartman
2020-03-03 9:52 ` Michael Ellerman
2020-03-06 0:27 ` [PATCH 1/6] powerpc: kernel: " Michael Ellerman
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