do_div is the wrong way to divide a sector_t, as it is less
efficient when sector_t is 32-bit wide. With the upcoming
do_div optimizations, the kernel starts warning about this:
drivers/scsi/scsi_debug.c: In function 'dif_store':
include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
This changes the code to use sector_div instead, which always
produces optimal code.
Signed-off-by: Arnd Bergmann <[email protected]>
---
Found on the ARM randconfig build today, after I merged Nico's patches
for linux-next
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index dfcc45bb03b1..ec622ba9864a 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
static struct sd_dif_tuple *dif_store(sector_t sector)
{
- sector = do_div(sector, sdebug_store_sectors);
+ sector = sector_div(sector, sdebug_store_sectors);
return dif_storep + sector;
}
@@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t lba)
lba += scsi_debug_unmap_granularity -
scsi_debug_unmap_alignment;
}
- do_div(lba, scsi_debug_unmap_granularity);
+ sector_div(lba, scsi_debug_unmap_granularity);
return lba;
}
On Fri, 2015-11-20 at 17:38 +0100, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
>
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct
> pointer types lacks a cast
>
> This changes the code to use sector_div instead, which always
> produces optimal code.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> Found on the ARM randconfig build today, after I merged Nico's
> patches
> for linux-next
>
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index dfcc45bb03b1..ec622ba9864a 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
>
> static struct sd_dif_tuple *dif_store(sector_t sector)
> {
> - sector = do_div(sector, sdebug_store_sectors);
> + sector = sector_div(sector, sdebug_store_sectors);
>
> return dif_storep + sector;
> }
> @@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t
> lba)
> lba += scsi_debug_unmap_granularity -
> scsi_debug_unmap_alignment;
> }
> - do_div(lba, scsi_debug_unmap_granularity);
> + sector_div(lba, scsi_debug_unmap_granularity);
>
> return lba;
> }
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-scsi"
> in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
Reviewed-by: Johannes Thumshirn <[email protected]>
On 20/11/2015 18:38, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
>
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
>
> This changes the code to use sector_div instead, which always
> produces optimal code.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Sagi Grimberg <[email protected]>
On 11/20/2015 05:38 PM, Arnd Bergmann wrote:
> do_div is the wrong way to divide a sector_t, as it is less
> efficient when sector_t is 32-bit wide. With the upcoming
> do_div optimizations, the kernel starts warning about this:
>
> drivers/scsi/scsi_debug.c: In function 'dif_store':
> include/asm-generic/div64.h:207:28: warning: comparison of distinct pointer types lacks a cast
>
> This changes the code to use sector_div instead, which always
> produces optimal code.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> Found on the ARM randconfig build today, after I merged Nico's patches
> for linux-next
>
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index dfcc45bb03b1..ec622ba9864a 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -678,7 +678,7 @@ static void *fake_store(unsigned long long lba)
>
> static struct sd_dif_tuple *dif_store(sector_t sector)
> {
> - sector = do_div(sector, sdebug_store_sectors);
> + sector = sector_div(sector, sdebug_store_sectors);
>
> return dif_storep + sector;
> }
> @@ -2780,7 +2780,7 @@ static unsigned long lba_to_map_index(sector_t lba)
> lba += scsi_debug_unmap_granularity -
> scsi_debug_unmap_alignment;
> }
> - do_div(lba, scsi_debug_unmap_granularity);
> + sector_div(lba, scsi_debug_unmap_granularity);
>
> return lba;
> }
>
Reviewed-by: Hannes Reinecke <[email protected]>
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
[email protected] +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
GF: F. Imend?rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG N?rnberg)
>>>>> "Arnd" == Arnd Bergmann <[email protected]> writes:
Arnd> do_div is the wrong way to divide a sector_t, as it is less
Arnd> efficient when sector_t is 32-bit wide. With the upcoming do_div
Arnd> optimizations, the kernel starts warning about this:
Applied.
--
Martin K. Petersen Oracle Linux Engineering