lib: scatterlist: Fix to support no mapped sg

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>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/sg_split.c b/lib/sg_split.c
index 9982c63d1063..60a0babebf2e 100644
--- a/lib/sg_split.c
+++ b/lib/sg_split.c
@@ -176,11 +176,13 @@ 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;