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SubjectRe: [PATCH 3/3] blk-throttle: don't parse cgroup path if trace isn't enabled
On Tue, 10 May 2016 11:52:15 -0400
Jeff Moyer <jmoyer@redhat.com> wrote:


> > +static inline bool blk_trace_note_message_enabled(struct request_queue *q)
> > +{
> > + struct blk_trace *bt = q->blk_trace;
> > + if (likely(!bt))
> > + return false;
> > + return bt->act_mask & BLK_TC_NOTIFY;
>
> Do we want to return !!(bt->act_mask & BLK_TC_NOTIFY)?

The return type is bool. I would think that gcc would be smart enough
to make the conversion.

To check, I compiled the following function:

bool testbool(int x)
{
return x & 1<<3;
}

and the result was:


0000000000000000 <testbool>:
0: 55 push %rbp
1: 48 89 e5 mov %rsp,%rbp
4: 89 7d fc mov %edi,-0x4(%rbp)
7: 8b 45 fc mov -0x4(%rbp),%eax
a: 83 e0 08 and $0x8,%eax
d: 85 c0 test %eax,%eax
f: 0f 95 c0 setne %al
12: 5d pop %rbp
13: c3 retq

I get the same by adding !!(x & 1<<3)

Looks like it does the conversion.

-- Steve

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