| Message ID | 20220815031228.64126-1-ye.xingchen@zte.com.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [linux-next] KVM:define vcpu_get_pid_fops with DEFINE_DEBUGFS_ATTRIBUTE | expand |
On Mon, Aug 15, 2022, cgel.zte@gmail.com wrote: > From: ye xingchen <ye.xingchen@zte.com.cn> > > From the coccinelle check: > ./virt/kvm/kvm_main.c line 3847 > WARNING vcpu_get_pid_fops should be defined with DEFINE_DEBUGFS_ATTRIBUTE > > Reported-by: Zeal Robot <zealci@zte.com.cn> > Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn> > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 515dfe9d3bcf..a0817179f8e4 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -3844,7 +3844,7 @@ static int vcpu_get_pid(void *data, u64 *val) > return 0; > } > > -DEFINE_SIMPLE_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); > +DEFINE_DEBUGFS_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); Based on the comments in scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci, it seems that using DEFINE_DEBUGFS_ATTRIBUTE is only beneficial if the file is created with debugfs_create_file_unsafe(). IIUC, using DEFINE_DEBUGFS_ATTRIBUTE without switching to debugfs_create_file_unsafe() will actually _add_ overhead. //# Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file() //# imposes some significant overhead as compared to //# DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe(). Using DEFINE_DEBUGFS_ATTRIBUTE also effectively drops ->llseek() support. I assume that's not a problem? But someone that knows how this is actually used should chime in.
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 515dfe9d3bcf..a0817179f8e4 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3844,7 +3844,7 @@ static int vcpu_get_pid(void *data, u64 *val) return 0; } -DEFINE_SIMPLE_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); +DEFINE_DEBUGFS_ATTRIBUTE(vcpu_get_pid_fops, vcpu_get_pid, NULL, "%llu\n"); static void kvm_create_vcpu_debugfs(struct kvm_vcpu *vcpu) {