2018-07-10 16:58:20

by Arnd Bergmann

Subject: [PATCH] block: iolatency: avoid 64-bit division

On 32-bit architectures, dividing a 64-bit number needs to use the
do_div() function or something like it to avoid a link failure:

block/blk-iolatency.o: In function `iolatency_prfill_limit':
blk-iolatency.c:(.text+0x8cc): undefined reference to `__aeabi_uldivmod'

Using div_u64() gives us the best output and avoids the need for an
explicit cast.

Fixes: d70675121546 ("block: introduce blk-iolatency io controller")
Signed-off-by: Arnd Bergmann <[email protected]>
---
block/blk-iolatency.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index a35a1f580337..56ddb2c68752 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -798,8 +798,7 @@ static u64 iolatency_prfill_limit(struct seq_file *sf,
if (!dname || !iolat->min_lat_nsec)
return 0;
seq_printf(sf, "%s target=%llu\n",
- dname,
- (unsigned long long)iolat->min_lat_nsec / NSEC_PER_USEC);
+ dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC));
return 0;
}

--
2.9.0

2018-07-10 18:18:31

by Josef Bacik

Subject: Re: [PATCH] block: iolatency: avoid 64-bit division

On Tue, Jul 10, 2018 at 05:21:34PM +0200, Arnd Bergmann wrote:
> On 32-bit architectures, dividing a 64-bit number needs to use the
> do_div() function or something like it to avoid a link failure:
>
> block/blk-iolatency.o: In function `iolatency_prfill_limit':
> blk-iolatency.c:(.text+0x8cc): undefined reference to `__aeabi_uldivmod'
>
> Using div_u64() gives us the best output and avoids the need for an
> explicit cast.
>
> Fixes: d70675121546 ("block: introduce blk-iolatency io controller")
> Signed-off-by: Arnd Bergmann <[email protected]>

Oops sorry Arnd,

Reviewed-by: Josef Bacik <[email protected]>

2018-07-10 18:30:34

by Jens Axboe

Subject: Re: [PATCH] block: iolatency: avoid 64-bit division

On 7/10/18 9:21 AM, Arnd Bergmann wrote:
> On 32-bit architectures, dividing a 64-bit number needs to use the
> do_div() function or something like it to avoid a link failure:
>
> block/blk-iolatency.o: In function `iolatency_prfill_limit':
> blk-iolatency.c:(.text+0x8cc): undefined reference to `__aeabi_uldivmod'
>
> Using div_u64() gives us the best output and avoids the need for an
> explicit cast.

Applied, thanks Arnd.

--
Jens Axboe