NVMe: Use PRP2 for the nvme_identify ioctl

DMA the result straight to userspace instead of bounce-buffering in the
kernel.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

1 files changed, 41 insertions, 17 deletions

diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c
index 44a9d5edd8db..c0ef1dd1cc90 100644
--- a/drivers/block/nvme.c
+++ b/drivers/block/nvme.c
@@ -647,33 +647,57 @@ static int __devinit nvme_configure_admin_queue(struct nvme_dev *dev)
         return result;
 }
 
-static int nvme_identify(struct nvme_ns *ns, void __user *addr, int cns)
+static int nvme_identify(struct nvme_ns *ns, unsigned long addr, int cns)
 {
         struct nvme_dev *dev = ns->dev;
-        int status;
+        int i, err, count, nents, offset;
         struct nvme_command c;
-        void *page;
-        dma_addr_t dma_addr;
-
-        page = dma_alloc_coherent(&dev->pci_dev->dev, 4096, &dma_addr,
-                                                                GFP_KERNEL);
+        struct scatterlist sg[2];
+        struct page *pages[2];
+
+        if (addr & 3)
+                return -EINVAL;
+        offset = offset_in_page(addr);
+        count = offset ? 2 : 1;
+
+        err = get_user_pages_fast(addr, count, 1, pages);
+        if (err < count) {
+                count = err;
+                err = -EFAULT;
+                goto put_pages;
+        }
+        sg_init_table(sg, count);
+        for (i = 0; i < count; i++)
+                sg_set_page(&sg[i], pages[i], PAGE_SIZE, 0);
+        nents = dma_map_sg(&dev->pci_dev->dev, sg, count, DMA_FROM_DEVICE);
+        if (!nents)
+                goto put_pages;
 
         memset(&c, 0, sizeof(c));
         c.identify.opcode = nvme_admin_identify;
         c.identify.nsid = cns ? 0 : cpu_to_le32(ns->ns_id);
-        c.identify.prp1 = cpu_to_le64(dma_addr);
+        c.identify.prp1 = cpu_to_le64(sg_dma_address(&sg[0]) + offset);
+        if (count > 1) {
+                u64 dma_addr;
+                if (nents > 1)
+                        dma_addr = sg_dma_address(&sg[1]);
+                else
+                        dma_addr = sg_dma_address(&sg[0]) + PAGE_SIZE;
+                c.identify.prp2 = cpu_to_le64(dma_addr);
+        }
         c.identify.cns = cpu_to_le32(cns);
 
-        status = nvme_submit_admin_cmd(dev, &c, NULL);
+        err = nvme_submit_admin_cmd(dev, &c, NULL);
 
-        if (status)
-                status = -EIO;
-        else if (copy_to_user(addr, page, 4096))
-                status = -EFAULT;
+        if (err)
+                err = -EIO;
 
-        dma_free_coherent(&dev->pci_dev->dev, 4096, page, dma_addr);
+        dma_unmap_sg(&dev->pci_dev->dev, sg, nents, DMA_FROM_DEVICE);
+ put_pages:
+        for (i = 0; i < count; i++)
+                put_page(pages[i]);
 
-        return status;
+        return err;
 }
 
 static int nvme_get_range_type(struct nvme_ns *ns, void __user *addr)
@@ -713,9 +737,9 @@ static int nvme_ioctl(struct block_device *bdev, fmode_t mode, unsigned int cmd,
 
         switch (cmd) {
         case NVME_IOCTL_IDENTIFY_NS:
-                return nvme_identify(ns, (void __user *)arg, 0);
+                return nvme_identify(ns, arg, 0);
         case NVME_IOCTL_IDENTIFY_CTRL:
-                return nvme_identify(ns, (void __user *)arg, 1);
+                return nvme_identify(ns, arg, 1);
         case NVME_IOCTL_GET_RANGE_TYPE:
                 return nvme_get_range_type(ns, (void __user *)arg);
         default: