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, 11 deletions

diff --git a/drivers/media/pci/ivtv/ivtv-yuv.c b/drivers/media/pci/ivtv/ivtv-yuv.c
index cd2fe2d444c0..5f7dc9771f8d 100644
--- a/drivers/media/pci/ivtv/ivtv-yuv.c
+++ b/drivers/media/pci/ivtv/ivtv-yuv.c
@@ -30,7 +30,6 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 	struct yuv_playback_info *yi = &itv->yuv_info;
 	u8 frame = yi->draw_frame;
 	struct yuv_frame_info *f = &yi->new_frame_info[frame];
-	int i;
 	int y_pages, uv_pages;
 	unsigned long y_buffer_offset, uv_buffer_offset;
 	int y_decode_height, uv_decode_height, y_size;
@@ -62,12 +61,12 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 	ivtv_udma_get_page_info (&y_dma, (unsigned long)args->y_source, 720 * y_decode_height);
 	ivtv_udma_get_page_info (&uv_dma, (unsigned long)args->uv_source, 360 * uv_decode_height);
 
-	/* Get user pages for DMA Xfer */
-	y_pages = get_user_pages_unlocked(y_dma.uaddr,
+	/* Pin user pages for DMA Xfer */
+	y_pages = pin_user_pages_unlocked(y_dma.uaddr,
 			y_dma.page_count, &dma->map[0], FOLL_FORCE);
 	uv_pages = 0; /* silence gcc. value is set and consumed only if: */
 	if (y_pages == y_dma.page_count) {
-		uv_pages = get_user_pages_unlocked(uv_dma.uaddr,
+		uv_pages = pin_user_pages_unlocked(uv_dma.uaddr,
 				uv_dma.page_count, &dma->map[y_pages],
 				FOLL_FORCE);
 	}
@@ -81,8 +80,7 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 				 uv_pages, uv_dma.page_count);
 
 			if (uv_pages >= 0) {
-				for (i = 0; i < uv_pages; i++)
-					put_page(dma->map[y_pages + i]);
+				unpin_user_pages(&dma->map[y_pages], uv_pages);
 				rc = -EFAULT;
 			} else {
 				rc = uv_pages;
@@ -93,8 +91,7 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 				 y_pages, y_dma.page_count);
 		}
 		if (y_pages >= 0) {
-			for (i = 0; i < y_pages; i++)
-				put_page(dma->map[i]);
+			unpin_user_pages(dma->map, y_pages);
 			/*
 			 * Inherit the -EFAULT from rc's
 			 * initialization, but allow it to be
@@ -112,9 +109,7 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
 	/* Fill & map SG List */
 	if (ivtv_udma_fill_sg_list (dma, &uv_dma, ivtv_udma_fill_sg_list (dma, &y_dma, 0)) < 0) {
 		IVTV_DEBUG_WARN("could not allocate bounce buffers for highmem userspace buffers\n");
-		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;
 	}