IA64: iommu uses sg_next with an invalid sg element

sg list elements might not be continuous.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
index 4338f4123f3..3c95f4184b9 100644
--- a/arch/ia64/hp/common/sba_iommu.c
+++ b/arch/ia64/hp/common/sba_iommu.c
@@ -1179,7 +1179,6 @@ sba_fill_pdir(
         u64 *pdirp = NULL;
         unsigned long dma_offset = 0;
 
-        dma_sg--;
         while (nents-- > 0) {
                 int     cnt = startsg->dma_length;
                 startsg->dma_length = 0;
@@ -1201,7 +1200,8 @@ sba_fill_pdir(
                         u32 pide = startsg->dma_address & ~PIDE_FLAG;
                         dma_offset = (unsigned long) pide & ~iovp_mask;
                         startsg->dma_address = 0;
-                        dma_sg = sg_next(dma_sg);
+                        if (n_mappings)
+                                dma_sg = sg_next(dma_sg);
                         dma_sg->dma_address = pide | ioc->ibase;
                         pdirp = &(ioc->pdir_base[pide >> iovp_shift]);
                         n_mappings++;