linux-kernel - Re: [PATCH 2/2] bitmap: sync tools with new bitmap allocation API

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Date:   Mon, 25 Jun 2018 01:45:22 +0300
From:   Yury Norov <ynorov@...iumnetworks.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Matthew Wilcox <willy@...radead.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        David Ahern <dsahern@...il.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Jin Yao <yao.jin@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Snitzer <snitzer@...hat.com>
Subject: Re: [PATCH 2/2] bitmap: sync tools with new bitmap allocation API

On Sun, Jun 24, 2018 at 02:31:03PM -0700, Dmitry Torokhov wrote:
> External Email
> 
> On Sat, Jun 23, 2018 at 10:35:02AM +0300, Yury Norov wrote:
> > On top of next-20180622 and Andy Shevchenko series:
> > https://lkml.org/lkml/2018/6/18/841
> >
> > The series mentioned above introduces helpers for bitmap allocation.
> > tools/ has its own bitmap_alloc() which differs from bitmap_alloc()
> > proposed in new kernel API, and is equivalent to bitmap_zalloc().
> > In this series tools is switched to new API.
> >
> > This is RFC because I didn't find counterpart free() call to some
> > bitmap_zalloc()'s. So I didn't convert them to bitmap_free(). Could
> > someone point me out? The functions are:
> > setup_nodes();
> > do_read_bitmap(); // Free is called, but only in fail path.
> 
> Yes, because if we succeed we effectively return allocated bitmap to the
> caller. You'd need to trace upwards and see how it all gets cleaned up.
> But given that this is userspace and is not expected to be long-lived,
> maybe nobody bothered freeing memory and we instead rely on the kernel
> to clean it all up when process terminates.
> 
> Thanks.
> 
> > memory_node__read();
> >
> > Signed-off-by: Yury Norov <ynorov@...iumnetworks.com>
> > ---
> >  tools/include/linux/bitmap.h | 19 +++++++++++++++----
> >  tools/perf/builtin-c2c.c     | 10 +++++-----
> >  tools/perf/tests/bitmap.c    |  4 ++--
> >  tools/perf/tests/mem2node.c  |  4 ++--
> >  tools/perf/util/header.c     |  6 +++---
> >  5 files changed, 27 insertions(+), 16 deletions(-)
> >
> > diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
> > index 48c208437bbd..b9b85b94c937 100644
> > --- a/tools/include/linux/bitmap.h
> > +++ b/tools/include/linux/bitmap.h
> > @@ -98,12 +98,23 @@ static inline int test_and_set_bit(int nr, unsigned long *addr)
> >  }
> >
> >  /**
> > - * bitmap_alloc - Allocate bitmap
> > - * @nbits: Number of bits
> > + * Allocation and deallocation of bitmap.
> >   */
> > -static inline unsigned long *bitmap_alloc(int nbits)
> > +static inline unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags)
> 
> This makes absolutely no sense for userspace API. What gfp_t even means
> here?
> 
> If you want to introduce bitmap_zalloc and bitmap_free it is fine but
> adding dummy parameters to match kernel API exactly is a folly.

Identical API makes easier porting the code from kernel to tools.
Refer for example declaration of kmalloc in:
tools/testing/radix-tree/linux.c
tools/testing/scatterlist/linux/mm.h
tools/virtio/linux/kernel.h
tools/virtio/ringtest/ptr_ring.c

Yury