linux-kernel - [PATCH 3.16.y-ckt 020/142] drm/radeon: use post-decrement in error handling

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Date:	Tue, 22 Mar 2016 10:39:09 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Alex Deucher <alexander.deucher@....com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 020/142] drm/radeon: use post-decrement in error handling

3.16.7-ckt26 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Rasmus Villemoes <linux@...musvillemoes.dk>

commit bc3f5d8c4ca01555820617eb3b6c0857e4df710d upstream.

We need to use post-decrement to get the pci_map_page undone also for
i==0, and to avoid some very unpleasant behaviour if pci_map_page
failed already at i==0.

Reviewed-by: Christian König <christian.koenig@....com>
Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/gpu/drm/radeon/radeon_ttm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 7555349e30da..c4675b9729c9 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -629,7 +629,7 @@ static int radeon_ttm_tt_populate(struct ttm_tt *ttm)
 						       0, PAGE_SIZE,
 						       PCI_DMA_BIDIRECTIONAL);
 		if (pci_dma_mapping_error(rdev->pdev, gtt->ttm.dma_address[i])) {
-			while (--i) {
+			while (i--) {
 				pci_unmap_page(rdev->pdev, gtt->ttm.dma_address[i],
 					       PAGE_SIZE, PCI_DMA_BIDIRECTIONAL);
 				gtt->ttm.dma_address[i] = 0;