nvme-pci: take sglist coalescing in dma_map_sg into account

Some iommu implementations can merge physically and/or virtually
contiguous segments inside sg_map_dma.  The NVMe SGL support does not take
this into account and will warn because of falling off a loop.  Pass the
number of mapped segments to nvme_pci_setup_sgls so that the SGL setup
can take the number of mapped segments into account.

Reported-by: Fangjian (Turing) <f.fangjian@huawei.com>
Fixes: a7a7cbe3 ("nvme-pci: add SGL support")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@rimberg.me>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 9 insertions, 12 deletions

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index a7e94cc3c70e..4276ebfff22b 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -725,20 +725,19 @@ static void nvme_pci_sgl_set_seg(struct nvme_sgl_desc *sge,
 }
 
 static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,
-                struct request *req, struct nvme_rw_command *cmd)
+                struct request *req, struct nvme_rw_command *cmd, int entries)
 {
         struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
-        int length = blk_rq_payload_bytes(req);
         struct dma_pool *pool;
         struct nvme_sgl_desc *sg_list;
         struct scatterlist *sg = iod->sg;
-        int entries = iod->nents, i = 0;
         dma_addr_t sgl_dma;
+        int i = 0;
 
         /* setting the transfer type as SGL */
         cmd->flags = NVME_CMD_SGL_METABUF;
 
-        if (length == sg_dma_len(sg)) {
+        if (entries == 1) {
                 nvme_pci_sgl_set_data(&cmd->dptr.sgl, sg);
                 return BLK_STS_OK;
         }
@@ -778,13 +777,9 @@ static blk_status_t nvme_pci_setup_sgls(struct nvme_dev *dev,
                 }
 
                 nvme_pci_sgl_set_data(&sg_list[i++], sg);
-
-                length -= sg_dma_len(sg);
                 sg = sg_next(sg);
-                entries--;
-        } while (length > 0);
+        } while (--entries > 0);
 
-        WARN_ON(entries > 0);
         return BLK_STS_OK;
 }
 
@@ -796,6 +791,7 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
         enum dma_data_direction dma_dir = rq_data_dir(req) ?
                         DMA_TO_DEVICE : DMA_FROM_DEVICE;
         blk_status_t ret = BLK_STS_IOERR;
+        int nr_mapped;
 
         sg_init_table(iod->sg, blk_rq_nr_phys_segments(req));
         iod->nents = blk_rq_map_sg(q, req, iod->sg);
@@ -803,12 +799,13 @@ static blk_status_t nvme_map_data(struct nvme_dev *dev, struct request *req,
                 goto out;
 
         ret = BLK_STS_RESOURCE;
-        if (!dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir,
-                                DMA_ATTR_NO_WARN))
+        nr_mapped = dma_map_sg_attrs(dev->dev, iod->sg, iod->nents, dma_dir,
+                        DMA_ATTR_NO_WARN);
+        if (!nr_mapped)
                 goto out;
 
         if (iod->use_sgl)
-                ret = nvme_pci_setup_sgls(dev, req, &cmnd->rw);
+                ret = nvme_pci_setup_sgls(dev, req, &cmnd->rw, nr_mapped);
         else
                 ret = nvme_pci_setup_prps(dev, req, &cmnd->rw);