netdev - RE: [PATCH v1] ocfs2/dlm: Move BITS_TO_BYTES() to bitops.h for wider use

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Message-ID: <MN2PR18MB2528511CEFCBC2BE07947BAAD3A50@MN2PR18MB2528.namprd18.prod.outlook.com>
Date:   Thu, 22 Aug 2019 05:46:07 +0000
From:   Sudarsana Reddy Kalluru <skalluru@...vell.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>
CC:     Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>,
        Ariel Elior <aelior@...vell.com>,
        GR-everest-linux-l2 <GR-everest-linux-l2@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Colin Ian King <colin.king@...onical.com>
Subject: RE: [PATCH v1] ocfs2/dlm: Move BITS_TO_BYTES() to bitops.h for wider
 use


> -----Original Message-----
> From: netdev-owner@...r.kernel.org <netdev-owner@...r.kernel.org> On
> Behalf Of Andy Shevchenko
> Sent: Wednesday, August 21, 2019 2:56 PM
> To: Joseph Qi <joseph.qi@...ux.alibaba.com>
> Cc: Mark Fasheh <mark@...heh.com>; Joel Becker <jlbec@...lplan.org>;
> ocfs2-devel@....oracle.com; Ariel Elior <aelior@...vell.com>; Sudarsana
> Reddy Kalluru <skalluru@...vell.com>; GR-everest-linux-l2 <GR-everest-
> linux-l2@...vell.com>; David S. Miller <davem@...emloft.net>;
> netdev@...r.kernel.org; Colin Ian King <colin.king@...onical.com>
> Subject: Re: [PATCH v1] ocfs2/dlm: Move BITS_TO_BYTES() to bitops.h for
> wider use
> 
> On Wed, Aug 21, 2019 at 09:29:04AM +0800, Joseph Qi wrote:
> > On 19/8/21 00:31, Andy Shevchenko wrote:
> > > There are users already and will be more of BITS_TO_BYTES() macro.
> > > Move it to bitops.h for wider use.
> > >
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > ---
> > >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_init.h | 1 -
> > >  fs/ocfs2/dlm/dlmcommon.h                         | 4 ----
> > >  include/linux/bitops.h                           | 1 +
> > >  3 files changed, 1 insertion(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_init.h
> > > b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_init.h
> > > index 066765fbef06..0a59a09ef82f 100644
> > > --- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_init.h
> > > +++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_init.h
> > > @@ -296,7 +296,6 @@ static inline void bnx2x_dcb_config_qm(struct
> bnx2x *bp, enum cos_mode mode,
> > >   *    possible, the driver should only write the valid vnics into the internal
> > >   *    ram according to the appropriate port mode.
> > >   */
> > > -#define BITS_TO_BYTES(x) ((x)/8)>
> > I don't think this is a equivalent replace, or it is in fact wrong
> > before?
> 
> I was thinking about this one and there are two applications:
> - calculus of the amount of structures of certain type per PAGE
>   (obviously off-by-one error in the original code IIUC purpose of
> STRUCT_SIZE)
> - calculus of some threshold based on line speed in bytes per second
>   (I dunno it will have any difference on the Gbs / 100 MBs speeds)
> 
I see that both the implementations (existing vs new) yield same value for standard speeds 10G (i.e.,10000), 1G (1000) that device supports. Hence the change look to be ok.

> > >  /* CMNG constants, as derived from system spec calculations */
> > >
> > > diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h
> > > index aaf24548b02a..0463dce65bb2 100644
> > > --- a/fs/ocfs2/dlm/dlmcommon.h
> > > +++ b/fs/ocfs2/dlm/dlmcommon.h
> > > @@ -688,10 +688,6 @@ struct dlm_begin_reco
> > >  	__be32 pad2;
> > >  };
> > >
> > > -
> > > -#define BITS_PER_BYTE 8
> > > -#define BITS_TO_BYTES(bits)
> > > (((bits)+BITS_PER_BYTE-1)/BITS_PER_BYTE)
> > > -
> > For ocfs2 part, it looks good to me.
> > Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
> 
> Thanks!
> 
> >
> > >  struct dlm_query_join_request
> > >  {
> > >  	u8 node_idx;
> > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h index
> > > cf074bce3eb3..79d80f5ddf7b 100644
> > > --- a/include/linux/bitops.h
> > > +++ b/include/linux/bitops.h
> > > @@ -5,6 +5,7 @@
> > >  #include <linux/bits.h>
> > >
> > >  #define BITS_PER_TYPE(type) (sizeof(type) * BITS_PER_BYTE)
> > > +#define BITS_TO_BYTES(nr)	DIV_ROUND_UP(nr, BITS_PER_BYTE)
> > >  #define BITS_TO_LONGS(nr)	DIV_ROUND_UP(nr,
> BITS_PER_TYPE(long))
> > >
> > >  extern unsigned int __sw_hweight8(unsigned int w);
> > >
> 
> --
> With Best Regards,
> Andy Shevchenko
>