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

This code was using get_user_pages*(), in a "Case 2" scenario
(DMA/RDMA), using the categorization from [1].  That means that it's
time to convert the get_user_pages*() + put_page() calls to
pin_user_pages*() + 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: Andy Walls <awalls@md.metrocast.net>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: http://lkml.kernel.org/r/20200518012157.1178336-3-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 13 deletions

diff --git a/drivers/media/pci/ivtv/ivtv-udma.c b/drivers/media/pci/ivtv/ivtv-udma.c
index 5f8883031c9c..0d8372cc364a 100644
--- a/drivers/media/pci/ivtv/ivtv-udma.c
+++ b/drivers/media/pci/ivtv/ivtv-udma.c
@@ -92,7 +92,7 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 {
 	struct ivtv_dma_page_info user_dma;
 	struct ivtv_user_dma *dma = &itv->udma;
-	int i, err;
+	int err;
 
 	IVTV_DEBUG_DMA("ivtv_udma_setup, dst: 0x%08x\n", (unsigned int)ivtv_dest_addr);
 
@@ -111,16 +111,15 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 		return -EINVAL;
 	}
 
-	/* Get user pages for DMA Xfer */
-	err = get_user_pages_unlocked(user_dma.uaddr, user_dma.page_count,
+	/* Pin user pages for DMA Xfer */
+	err = pin_user_pages_unlocked(user_dma.uaddr, user_dma.page_count,
 			dma->map, FOLL_FORCE);
 
 	if (user_dma.page_count != err) {
 		IVTV_DEBUG_WARN("failed to map user pages, returned %d instead of %d\n",
 			   err, user_dma.page_count);
 		if (err >= 0) {
-			for (i = 0; i < err; i++)
-				put_page(dma->map[i]);
+			unpin_user_pages(dma->map, err);
 			return -EINVAL;
 		}
 		return err;
@@ -130,9 +129,7 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 
 	/* Fill SG List with new values */
 	if (ivtv_udma_fill_sg_list(dma, &user_dma, 0) < 0) {
-		for (i = 0; i < dma->page_count; i++) {
-			put_page(dma->map[i]);
-		}
+		unpin_user_pages(dma->map, dma->page_count);
 		dma->page_count = 0;
 		return -ENOMEM;
 	}
@@ -153,7 +150,6 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
 void ivtv_udma_unmap(struct ivtv *itv)
 {
 	struct ivtv_user_dma *dma = &itv->udma;
-	int i;
 
 	IVTV_DEBUG_INFO("ivtv_unmap_user_dma\n");
 
@@ -169,10 +165,7 @@ void ivtv_udma_unmap(struct ivtv *itv)
 	/* sync DMA */
 	ivtv_udma_sync_for_cpu(itv);
 
-	/* Release User Pages */
-	for (i = 0; i < dma->page_count; i++) {
-		put_page(dma->map[i]);
-	}
+	unpin_user_pages(dma->map, dma->page_count);
 	dma->page_count = 0;
 }