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Message-ID: <20230814161731.GN776869@hirez.programming.kicks-ass.net>
Date: Mon, 14 Aug 2023 18:17:31 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Dan Williams <dan.j.williams@...el.com>,
linux-coco@...ts.linux.dev,
Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] mm/slab: Add __free() support for kvfree
On Mon, Aug 14, 2023 at 05:31:27PM +0200, Greg Kroah-Hartman wrote:
> On Mon, Aug 14, 2023 at 12:43:32AM -0700, Dan Williams wrote:
> > Allow for the declaration of variables that trigger kvfree() when they
> > go out of scope.
> >
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > ---
> > include/linux/slab.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 848c7c82ad5a..241025367943 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -746,6 +746,8 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
> > extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
> > __realloc_size(3);
> > extern void kvfree(const void *addr);
> > +DEFINE_FREE(kvfree, void *, if (_T) kvfree(_T))
>
> No need to check _T before calling this, right (as was also pointed out
> earlier).
Well, that does mean you get an unconditional call to kvfree() in the
success case. Linus argued against this.
This way the compiler sees:
buf = NULL;
if (buf)
kvfree(buf);
and goes: 'let me clean that up for you'. And all is well.
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