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

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Date:   Wed, 21 Aug 2019 12:25:41 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
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 Kalluru <skalluru@...vell.com>,
        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)

> >  /* 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