linux-kernel - Re: [PATCH] nfs: fix a couple of minor portability issues

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Date:	Wed, 10 Aug 2011 15:02:04 -0700
From:	Boaz Harrosh <bharrosh@...asas.com>
To:	Chris Metcalf <cmetcalf@...era.com>
CC:	Trond Myklebust <Trond.Myklebust@...app.com>,
	<linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nfs: fix a couple of minor portability issues

On 08/10/2011 10:56 AM, Chris Metcalf wrote:
> Building on tilepro revealed two minor portability issues: the
> blocklayout.c file used prefetchw() without #include <linux/prefetch.h>,
> and the nfs4filelayout.c file used do_div() on an s64 not a u64.
> This change fixes those two issues so the NFS code builds on tilepro.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
> ---
>  fs/nfs/blocklayout/blocklayout.c |    1 +
>  fs/nfs/nfs4filelayout.c          |    6 +++---
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index e56564d..9561c8f 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -36,6 +36,7 @@
>  #include <linux/namei.h>
>  #include <linux/bio.h>		/* struct bio */
>  #include <linux/buffer_head.h>	/* various write calls */
> +#include <linux/prefetch.h>
>  
>  #include "blocklayout.h"
>  
> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
> index e8915d4..6976a72 100644
> --- a/fs/nfs/nfs4filelayout.c
> +++ b/fs/nfs/nfs4filelayout.c
> @@ -48,13 +48,13 @@ filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
>  			    loff_t offset)
>  {
>  	u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
> -	u64 tmp;
> +	u64 tmp, uoff;
>  
>  	offset -= flseg->pattern_offset;
> -	tmp = offset;
> +	tmp = uoff = offset;
>  	do_div(tmp, stripe_width);
>  
> -	return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
> +	return tmp * flseg->stripe_unit + do_div(uoff, flseg->stripe_unit);

For proper u64 divisions it is best to use the div_u64 (and div64_u64) and not
use do_div. (And please don't add an unnecessary variable, just use a cast)

Thanks
Boaz

>  }
>  
>  /* This function is used by the layout driver to calculate the

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