netdev - RE: [PATCH v2] ocfs2/dlm: Move BITS_TO_BYTES() to bitops.h for wider use

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Date:   Wed, 11 Dec 2019 03:32:00 +0000
From:   Sudarsana Reddy Kalluru <skalluru@...vell.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        "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 v2] 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: Monday, December 9, 2019 10:14 PM
> To: Mark Fasheh <mark@...heh.com>; Joel Becker <jlbec@...lplan.org>;
> Joseph Qi <joseph.qi@...ux.alibaba.com>; 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 v2] ocfs2/dlm: Move BITS_TO_BYTES() to bitops.h for
> wider use
> 
> On Tue, Aug 27, 2019 at 07:37:17PM +0300, Andy Shevchenko wrote:
> > There are users already and will be more of BITS_TO_BYTES() macro.
> > Move it to bitops.h for wider use.
> >
> > In the case of ocfs2 the replacement is identical.
> >
> > As for bnx2x, there are two places where floor version is used.
> > In the first case to calculate the amount of structures that can fit
> > one memory page. In this case obviously the ceiling variant is correct
> > and original code might have a potential bug, if amount of bits % 8 is not 0.
> > In the second case the macro is used to calculate bytes transmitted in
> > one microsecond. This will work for all speeds which is multiply of
> > 1Gbps without any change, for the rest new code will give ceiling
> > value, for instance 100Mbps will give 13 bytes, while old code gives
> > 12 bytes and the arithmetically correct one is 12.5 bytes. Further the
> > value is used to setup timer threshold which in any case has its own
> > margins due to certain resolution. I don't see here an issue with
> > slightly shifting thresholds for low speed connections, the card is supposed
> to utilize highest available rate, which is usually 10Gbps.
> 
> Anybody to comment on bnx2 change?
> Can we survive with this applied?
> 
> >
> > Reviewed-by: Joseph Qi <joseph.qi@...ux.alibaba.com>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > ---
> > - described bnx2x cases in the commit message
> > - appended Rb (for ocfs2)
> >
> >  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)
> >
> >  /* 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)
> > -
> >  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);
> > --
> > 2.23.0.rc1
> >
> 
> --
> With Best Regards,
> Andy Shevchenko
> 

Thanks for the changes.

Acked-by: Sudarsana Reddy Kalluru <skalluru@...vell.com>