linux-kernel - Re: [PATCH 15/19] perf: Fix perf

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Message-ID: <21acdcec-a256-4309-a6b8-891c97a46f42@lucifer.local>
Date: Mon, 3 Mar 2025 12:38:38 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, lucas.demarchi@...el.com,
        linux-kernel@...r.kernel.org, willy@...radead.org, acme@...nel.org,
        namhyung@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        irogers@...gle.com, adrian.hunter@...el.com, kan.liang@...ux.intel.com
Subject: Re: [PATCH 15/19] perf: Fix perf_mmap() failure path

On Sat, Mar 01, 2025 at 08:17:02PM +0100, Ingo Molnar wrote:
>
> * Peter Zijlstra <peterz@...radead.org> wrote:
>
> > When f_ops->mmap() returns failure, m_ops->close() is *not* called.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> >  kernel/events/core.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > --- a/kernel/events/core.c
> > +++ b/kernel/events/core.c
> > @@ -6830,7 +6830,7 @@ static int perf_mmap(struct file *file,
> >  	vm_flags_set(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP);
> >  	vma->vm_ops = &perf_mmap_vmops;
> >
> > -	if (event->pmu->event_mapped)
> > +	if (!ret && event->pmu->event_mapped)
> >  		event->pmu->event_mapped(event, vma->vm_mm);
> >
> >  	return ret;
>
> I'm wondering whether this fix is still relevant in context of this
> recent commit:
>
>    b709eb872e19 perf: map pages in advance

Yeah this is, as perf_mmap() will still be triggered by the mmap code when
this is mmap'd, all we do is essentially prefault the pages at this point
also.

>
> Thanks,
>
> 	Ingo