[PATCH] nfs: fix a couple of minor portability issues

[PATCH] nfs: fix a couple of minor portability issues

[Chris Metcalf]

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@tilera.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);
 }
 
 /* This function is used by the layout driver to calculate the
-- 
1.6.5.2

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

[Boaz Harrosh]

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@tilera.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

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

[Chris Metcalf]

On 8/10/2011 6:02 PM, Boaz Harrosh wrote:
> 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.
>>
>> [...] 
>> 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)

You can't use a cast with do_div() or you get errors about non-lvalues.

And the context here is that we want the remainder, not the divided result,
so we'd need a temporary variable anyway if we were going to use a routine
from math64.h, presumably div_u64_rem().  But that's just an inline wrapper
around do_div() anyway, so it's no more efficient, and not obviously any
less "cluttered" in the source code here.  The original code author (who
I'm adding belatedly to this email) may have a stronger opinion.

I'm not the author or maintainer of this code, I just want it to compile
without warning on 32-bit architectures :-)

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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

[Peng Tao]

On Thu, Aug 11, 2011 at 1:56 AM, Chris Metcalf <cmetcalf@tilera.com> 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@tilera.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>
This is already fixed in Trond's nfs-for-next branch by commit 88c9e4219.

>
>  #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);
>  }
>
>  /* This function is used by the layout driver to calculate the
> --
> 1.6.5.2
>
> --
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>



-- 
Thanks,
-Bergwolf

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

[Boaz Harrosh]

On 08/11/2011 06:26 AM, Chris Metcalf wrote:
> 
> You can't use a cast with do_div() or you get errors about non-lvalues.
> 
> And the context here is that we want the remainder, not the divided result,
> so we'd need a temporary variable anyway if we were going to use a routine
> from math64.h, presumably div_u64_rem().  But that's just an inline wrapper
> around do_div() anyway, so it's no more efficient, and not obviously any
> less "cluttered" in the source code here.  The original code author (who
> I'm adding belatedly to this email) may have a stronger opinion.
> 
> I'm not the author or maintainer of this code, I just want it to compile
> without warning on 32-bit architectures :-)
> 

Still, if you fix it do it properly by using, as you said, div_u64_rem().
It's what needs to be used with u64 types.

Thanks
Boaz

[PATCH v2] nfs: fix a minor do_div portability issue

[Chris Metcalf]

This change modifies filelayout_get_dense_offset() to use the functions
in math64.h and thus avoid a 32-bit platform compile error trying to
use do_div() on an s64 type.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: Boaz Harrosh <bharrosh@panasas.com>
---
 fs/nfs/nfs4filelayout.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
index e8915d4..3ecb14f 100644
--- a/fs/nfs/nfs4filelayout.c
+++ b/fs/nfs/nfs4filelayout.c
@@ -49,12 +49,13 @@ filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
 {
 	u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
 	u64 tmp;
+	u32 rem;
 
 	offset -= flseg->pattern_offset;
-	tmp = offset;
-	do_div(tmp, stripe_width);
+	tmp = div_u64(offset, stripe_width);
+	div_u64_rem(offset, flseg->stripe_unit, &rem);
 
-	return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
+	return tmp * flseg->stripe_unit + rem;
 }
 
 /* This function is used by the layout driver to calculate the
-- 
1.6.5.2

[PATCH v3] nfs: fix a minor do_div portability issue

[Boaz Harrosh]

On 08/11/2011 12:32 PM, Chris Metcalf wrote:
> This change modifies filelayout_get_dense_offset() to use the functions
> in math64.h and thus avoid a 32-bit platform compile error trying to
> use do_div() on an s64 type.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
> Cc: Boaz Harrosh <bharrosh@panasas.com>

Thanks
Reviewed-by: Boaz Harrosh <bharrosh@panasas.com>

Just if you don't mind a name change. tmp => stripe_no
while at it.

---
From: Chris Metcalf <cmetcalf@tilera.com>
Subject: [PATCH v3] nfs: fix a minor do_div portability issue


This change modifies filelayout_get_dense_offset() to use the functions
in math64.h and thus avoid a 32-bit platform compile error trying to
use do_div() on an s64 type.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Reviewed-by: Boaz Harrosh <bharrosh@panasas.com>
---
 fs/nfs/nfs4filelayout.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
index e8915d4..3ecb14f 100644
--- a/fs/nfs/nfs4filelayout.c
+++ b/fs/nfs/nfs4filelayout.c
@@ -49,12 +49,13 @@ filelayout_get_dense_offset(struct nfs4_filelayout_segment *flseg,
 {
 	u32 stripe_width = flseg->stripe_unit * flseg->dsaddr->stripe_count;
 	u64 stripe_no;
+	u32 rem;
 
 	offset -= flseg->pattern_offset;
-	tmp = offset;
-	do_div(tmp, stripe_width);
+	stripe_no = div_u64(offset, stripe_width);
+	div_u64_rem(offset, flseg->stripe_unit, &rem);
 
-	return tmp * flseg->stripe_unit + do_div(offset, flseg->stripe_unit);
+	return stripe_no * flseg->stripe_unit + rem;
 }
 
 /* This function is used by the layout driver to calculate the
-- 1.6.5.2