[PATCH v19 17/30] drm/panfrost: Fix the error path in panfrost_mmu_map_fault_addr()

[Dmitry Osipenko]

From: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>

If some the pages or sgt allocation failed, we shouldn't release the
pages ref we got earlier, otherwise we will end up with unbalanced
get/put_pages() calls. We should instead leave everything in place
and let the BO release function deal with extra cleanup when the object
is destroyed, or let the fault handler try again next time it's called.

Fixes: 187d2929206e ("drm/panfrost: Add support for GPU heap allocations")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
Co-developed-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/panfrost/panfrost_mmu.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
index bd5a0073009d..4a0b4bf03f1a 100644
--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -502,11 +502,18 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	mapping_set_unevictable(mapping);
 
 	for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) {
+		/* Can happen if the last fault only partially filled this
+		 * section of the pages array before failing. In that case
+		 * we skip already filled pages.
+		 */
+		if (pages[i])
+			continue;
+
 		pages[i] = shmem_read_mapping_page(mapping, i);
 		if (IS_ERR(pages[i])) {
 			ret = PTR_ERR(pages[i]);
 			pages[i] = NULL;
-			goto err_pages;
+			goto err_unlock;
 		}
 	}
 
@@ -514,7 +521,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
 					NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL);
 	if (ret)
-		goto err_pages;
+		goto err_unlock;
 
 	ret = dma_map_sgtable(pfdev->dev, sgt, DMA_BIDIRECTIONAL, 0);
 	if (ret)
@@ -537,8 +544,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 
 err_map:
 	sg_free_table(sgt);
-err_pages:
-	drm_gem_shmem_put_pages_locked(&bo->base);
 err_unlock:
 	dma_resv_unlock(obj->resv);
 err_bo:
-- 
2.43.0