[PATCH v2 21/21] dma-mapping: Disallow .map_sg operations from returning zero on error

[Logan Gunthorpe <logang@xxxxxxxxxxxx>]

Now that all the .map_sg operations have been converted to returning
proper error codes, drop the code to handle a zero return value,
add a warning if a zero is returned and update the comment for the
map_sg operation.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
 kernel/dma/mapping.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index b8dc8b1cb402..86a8a421344a 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -194,6 +194,9 @@ static int __dma_map_sg_attrs(struct device *dev, struct 
scatterlist *sg,
        else
                ents = ops->map_sg(dev, sg, nents, dir, attrs);
 
+       if (WARN_ON_ONCE(ents == 0))
+               return -EIO;
+
        if (ents > 0)
                debug_dma_map_sg(dev, sg, nents, ents, dir);
 
@@ -259,9 +262,7 @@ int dma_map_sgtable(struct device *dev, struct sg_table 
*sgt,
        int nents;
 
        nents = __dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);
-       if (nents == 0)
-               return -EIO;
-       else if (nents < 0) {
+       if (nents < 0) {
                if (WARN_ON_ONCE(nents != -EINVAL && nents != -ENOMEM &&
                                 nents != -EIO))
                        return -EIO;
-- 
2.20.1