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>

diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c
index 44a9d5e..c0ef1dd 100644 (file)
--- 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: