block: iolatency: avoid 64-bit division
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Message ID 20180710152146.2371336-1-arnd@arndb.de
State New
Headers show

Commit Message

Arnd Bergmann July 10, 2018, 3:21 p.m. UTC
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 <arnd@arndb.de>
---
 block/blk-iolatency.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Comments

Josef Bacik July 10, 2018, 6:16 p.m. UTC | #1
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 <arnd@arndb.de>

Oops sorry Arnd,

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Jens Axboe July 10, 2018, 6:28 p.m. UTC | #2
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.

Patch
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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;
 }