[PATCH] lib: scatterlist: Fix to support no mapped sg

[PATCH] lib: scatterlist: Fix to support no mapped sg

[Zhou Wang]

In function sg_split, the second sg_calculate_split will return -EINVAL
when in_mapped_nents is 0.

Indeed there is no need to do second sg_calculate_split and sg_split_mapped
when in_mapped_nents is 0, as in_mapped_nents indicates no mapped entry in
original sgl.

Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
---
 lib/sg_split.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/lib/sg_split.c b/lib/sg_split.c
index b063410..d4181c8 100644
--- a/lib/sg_split.c
+++ b/lib/sg_split.c
@@ -178,11 +178,13 @@ int sg_split(struct scatterlist *in, const int in_mapped_nents,
 	 * The order of these 3 calls is important and should be kept.
 	 */
 	sg_split_phys(splitters, nb_splits);
-	ret = sg_calculate_split(in, in_mapped_nents, nb_splits, skip,
-				 split_sizes, splitters, true);
-	if (ret < 0)
-		goto err;
-	sg_split_mapped(splitters, nb_splits);
+	if (in_mapped_nents) {
+		ret = sg_calculate_split(in, in_mapped_nents, nb_splits, skip,
+					 split_sizes, splitters, true);
+		if (ret < 0)
+			goto err;
+		sg_split_mapped(splitters, nb_splits);
+	}
 
 	for (i = 0; i < nb_splits; i++) {
 		out[i] = splitters[i].out_sg;
-- 
2.8.1

Re: [PATCH] lib: scatterlist: Fix to support no mapped sg

[Robert Jarzmik]

Zhou Wang <wangzhou1@hisilicon.com> writes:

> In function sg_split, the second sg_calculate_split will return -EINVAL
> when in_mapped_nents is 0.
>
> Indeed there is no need to do second sg_calculate_split and sg_split_mapped
> when in_mapped_nents is 0, as in_mapped_nents indicates no mapped entry in
> original sgl.
>
> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
That's right. May I know what is the usecase which led you to this fix ?

Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>

--
Robert

Re: [PATCH] lib: scatterlist: Fix to support no mapped sg

[Zhou Wang]

On 2019/4/19 18:43, Robert Jarzmik wrote:
> Zhou Wang <wangzhou1@hisilicon.com> writes:
> 
>> In function sg_split, the second sg_calculate_split will return -EINVAL
>> when in_mapped_nents is 0.
>>
>> Indeed there is no need to do second sg_calculate_split and sg_split_mapped
>> when in_mapped_nents is 0, as in_mapped_nents indicates no mapped entry in
>> original sgl.
>>
>> Signed-off-by: Zhou Wang <wangzhou1@hisilicon.com>
> That's right. May I know what is the usecase which led you to this fix ?

I posted a patchset to support HiSilicon compression engine:
https://lkml.org/lkml/2019/1/23/358. As Herber Xu suggested, it should use
new crypto acomp API which uses sgl as data input and output. However, our
hardware can not handle compress head for input/output data, so I need split
input/output sgl firstly which is not mapped sgl.

New version of HiSilicon compression engine driver has not been posted to
community yet. I will do this later.

> 
> Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>

Many thanks for your review,
Zhou

> 
> --
> Robert
> 
> .
>