linux-kernel - Re: misuse of fget_raw() in perf_event

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Message-ID: <20190415090406.GJ2490@worktop.programming.kicks-ass.net>
Date:   Mon, 15 Apr 2019 11:04:06 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, tj@...nel.org
Subject: Re: misuse of fget_raw() in perf_event_get()

On Sun, Apr 14, 2019 at 09:42:00PM -0700, Alexei Starovoitov wrote:
> On Sat, Apr 13, 2019 at 10:02:42PM +0100, Al Viro wrote:
> > 	What's the point of using fget_raw(), if you do
> > _not_ accept O_PATH descriptors?  That should be fget()...
> 
> I think you're talking about commit e03e7ee34fdd ("perf/bpf: Convert perf_event_array to use struct file")
> I don't really remember why we went with this instead of fget().
> There was a bunch of back and forth back then with Peter.

That was mostly on what refcount to use, you wanted to use the event
refcount, and I suggested using the file refcount.

If you look at:

  lkml.kernel.org/r/20160126161637.GF6357@...ns.programming.kicks-ass.net

I too wondered about the fget_raw() at the time, whatever Al wants
though, I never quite remember how that file stuff works :/