rapidio: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages_fast(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1].  That means that it's time
to convert the get_user_pages_fast() + put_page() calls to
pin_user_pages_fast() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small
part of fixing a long-standing disconnect between pinning pages, and
file systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Alexandre Bounine <alex.bou9@gmail.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Link: http://lkml.kernel.org/r/20200517235620.205225-3-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/rapidio/devices/rio_mport_cdev.c b/drivers/rapidio/devices/rio_mport_cdev.c
index 0b85a80ae7ef626f7265e2241f69512e93fa2f06..451608e960a1823287f3afa6ec48a7312cf1f2a3 100644 (file)
--- a/drivers/rapidio/devices/rio_mport_cdev.c
+++ b/drivers/rapidio/devices/rio_mport_cdev.c
@@ -572,14 +572,12 @@ static void dma_req_free(struct kref *ref)
        struct mport_dma_req *req = container_of(ref, struct mport_dma_req,
                        refcount);
        struct mport_cdev_priv *priv = req->priv;
-       unsigned int i;
 
        dma_unmap_sg(req->dmach->device->dev,
                     req->sgt.sgl, req->sgt.nents, req->dir);
        sg_free_table(&req->sgt);
        if (req->page_list) {
-               for (i = 0; i < req->nr_pages; i++)
-                       put_page(req->page_list[i]);
+               unpin_user_pages(req->page_list, req->nr_pages);
                kfree(req->page_list);
        }
 
@@ -815,7 +813,7 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
        struct mport_dma_req *req;
        struct mport_dev *md = priv->md;
        struct dma_chan *chan;
-       int i, ret;
+       int ret;
        int nents;
 
        if (xfer->length == 0)
@@ -862,7 +860,7 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
                        goto err_req;
                }
 
-               pinned = get_user_pages_fast(
+               pinned = pin_user_pages_fast(
                                (unsigned long)xfer->loc_addr & PAGE_MASK,
                                nr_pages,
                                dir == DMA_FROM_DEVICE ? FOLL_WRITE : 0,
@@ -870,7 +868,7 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
 
                if (pinned != nr_pages) {
                        if (pinned < 0) {
-                               rmcd_error("get_user_pages_unlocked err=%ld",
+                               rmcd_error("pin_user_pages_fast err=%ld",
                                           pinned);
                                nr_pages = 0;
                        } else
@@ -951,8 +949,7 @@ rio_dma_transfer(struct file *filp, u32 transfer_mode,
 
 err_pg:
        if (!req->page_list) {
-               for (i = 0; i < nr_pages; i++)
-                       put_page(page_list[i]);
+               unpin_user_pages(page_list, nr_pages);
                kfree(page_list);
        }
 err_req: