Revert "drm/shmem-helper: Switch to reservation lock"

This reverts commit 67b7836d.

The locking appears incomplete. A caller of SHMEM helper's pin
function never acquires the dma-buf reservation lock. So we get

  WARNING: CPU: 3 PID: 967 at drivers/gpu/drm/drm_gem_shmem_helper.c:243 drm_gem_shmem_pin+0x42/0x90 [drm_shmem_helper]
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230228152612.19971-1-tzimmermann@suse.de

drivers/gpu/drm/lima/lima_gem.c

@@ -34,7 +34,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 
 	new_size = min(new_size, bo->base.base.size);
 
-	dma_resv_lock(bo->base.base.resv, NULL);
+	mutex_lock(&bo->base.pages_lock);
 
 	if (bo->base.pages) {
 		pages = bo->base.pages;
@@ -42,7 +42,7 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		pages = kvmalloc_array(bo->base.base.size >> PAGE_SHIFT,
 				       sizeof(*pages), GFP_KERNEL | __GFP_ZERO);
 		if (!pages) {
-			dma_resv_unlock(bo->base.base.resv);
+			mutex_unlock(&bo->base.pages_lock);
 			return -ENOMEM;
 		}
 
@@ -56,13 +56,13 @@ int lima_heap_alloc(struct lima_bo *bo, struct lima_vm *vm)
 		struct page *page = shmem_read_mapping_page(mapping, i);
 
 		if (IS_ERR(page)) {
-			dma_resv_unlock(bo->base.base.resv);
+			mutex_unlock(&bo->base.pages_lock);
 			return PTR_ERR(page);
 		}
 		pages[i] = page;
 	}
 
-	dma_resv_unlock(bo->base.base.resv);
+	mutex_unlock(&bo->base.pages_lock);
 
 	ret = sg_alloc_table_from_pages(&sgt, pages, i, 0,
 					new_size, GFP_KERNEL);

drivers/gpu/drm/panfrost/panfrost_drv.c

@@ -407,10 +407,6 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 
 	bo = to_panfrost_bo(gem_obj);
 
-	ret = dma_resv_lock_interruptible(bo->base.base.resv, NULL);
-	if (ret)
-		goto out_put_object;
-
 	mutex_lock(&pfdev->shrinker_lock);
 	mutex_lock(&bo->mappings.lock);
 	if (args->madv == PANFROST_MADV_DONTNEED) {
@@ -448,8 +444,7 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
 out_unlock_mappings:
 	mutex_unlock(&bo->mappings.lock);
 	mutex_unlock(&pfdev->shrinker_lock);
-	dma_resv_unlock(bo->base.base.resv);
-out_put_object:
+
 	drm_gem_object_put(gem_obj);
 	return ret;
 }

drivers/gpu/drm/panfrost/panfrost_gem_shrinker.c

@@ -48,14 +48,14 @@ static bool panfrost_gem_purge(struct drm_gem_object *obj)
 	if (!mutex_trylock(&bo->mappings.lock))
 		return false;
 
-	if (!dma_resv_trylock(shmem->base.resv))
+	if (!mutex_trylock(&shmem->pages_lock))
 		goto unlock_mappings;
 
 	panfrost_gem_teardown_mappings_locked(bo);
-	drm_gem_shmem_purge(&bo->base);
+	drm_gem_shmem_purge_locked(&bo->base);
 	ret = true;
 
-	dma_resv_unlock(shmem->base.resv);
+	mutex_unlock(&shmem->pages_lock);
 
 unlock_mappings:
 	mutex_unlock(&bo->mappings.lock);

drivers/gpu/drm/panfrost/panfrost_mmu.c

@@ -443,7 +443,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	struct panfrost_gem_mapping *bomapping;
 	struct panfrost_gem_object *bo;
 	struct address_space *mapping;
-	struct drm_gem_object *obj;
 	pgoff_t page_offset;
 	struct sg_table *sgt;
 	struct page **pages;
@@ -466,16 +465,15 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	page_offset = addr >> PAGE_SHIFT;
 	page_offset -= bomapping->mmnode.start;
 
-	obj = &bo->base.base;
-
-	dma_resv_lock(obj->resv, NULL);
+	mutex_lock(&bo->base.pages_lock);
 
 	if (!bo->base.pages) {
 		bo->sgts = kvmalloc_array(bo->base.base.size / SZ_2M,
 				     sizeof(struct sg_table), GFP_KERNEL | __GFP_ZERO);
 		if (!bo->sgts) {
+			mutex_unlock(&bo->base.pages_lock);
 			ret = -ENOMEM;
-			goto err_unlock;
+			goto err_bo;
 		}
 
 		pages = kvmalloc_array(bo->base.base.size >> PAGE_SHIFT,
@@ -483,8 +481,9 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 		if (!pages) {
 			kvfree(bo->sgts);
 			bo->sgts = NULL;
+			mutex_unlock(&bo->base.pages_lock);
 			ret = -ENOMEM;
-			goto err_unlock;
+			goto err_bo;
 		}
 		bo->base.pages = pages;
 		bo->base.pages_use_count = 1;
@@ -492,6 +491,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 		pages = bo->base.pages;
 		if (pages[page_offset]) {
 			/* Pages are already mapped, bail out. */
+			mutex_unlock(&bo->base.pages_lock);
 			goto out;
 		}
 	}
@@ -502,11 +502,14 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	for (i = page_offset; i < page_offset + NUM_FAULT_PAGES; i++) {
 		pages[i] = shmem_read_mapping_page(mapping, i);
 		if (IS_ERR(pages[i])) {
+			mutex_unlock(&bo->base.pages_lock);
 			ret = PTR_ERR(pages[i]);
 			goto err_pages;
 		}
 	}
 
+	mutex_unlock(&bo->base.pages_lock);
+
 	sgt = &bo->sgts[page_offset / (SZ_2M / PAGE_SIZE)];
 	ret = sg_alloc_table_from_pages(sgt, pages + page_offset,
 					NUM_FAULT_PAGES, 0, SZ_2M, GFP_KERNEL);
@@ -525,8 +528,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
 
 out:
-	dma_resv_unlock(obj->resv);
-
 	panfrost_gem_mapping_put(bomapping);
 
 	return 0;
@@ -535,8 +536,6 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
 	sg_free_table(sgt);
 err_pages:
 	drm_gem_shmem_put_pages(&bo->base);
-err_unlock:
-	dma_resv_unlock(obj->resv);
 err_bo:
 	panfrost_gem_mapping_put(bomapping);
 	return ret;

include/drm/drm_gem_shmem_helper.h

@@ -26,6 +26,11 @@ struct drm_gem_shmem_object {
 	 */
 	struct drm_gem_object base;
 
+	/**
+	 * @pages_lock: Protects the page table and use count
+	 */
+	struct mutex pages_lock;
+
 	/**
 	 * @pages: Page table
 	 */
@@ -60,6 +65,11 @@ struct drm_gem_shmem_object {
 	 */
 	struct sg_table *sgt;
 
+	/**
+	 * @vmap_lock: Protects the vmap address and use count
+	 */
+	struct mutex vmap_lock;
+
 	/**
 	 * @vaddr: Kernel virtual address of the backing memory
 	 */
@@ -99,6 +109,7 @@ struct drm_gem_shmem_object {
 struct drm_gem_shmem_object *drm_gem_shmem_create(struct drm_device *dev, size_t size);
 void drm_gem_shmem_free(struct drm_gem_shmem_object *shmem);
 
+int drm_gem_shmem_get_pages(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem);
 int drm_gem_shmem_pin(struct drm_gem_shmem_object *shmem);
 void drm_gem_shmem_unpin(struct drm_gem_shmem_object *shmem);
@@ -117,7 +128,8 @@ static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem
 		!shmem->base.dma_buf && !shmem->base.import_attach;
 }
 
-void drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
+void drm_gem_shmem_purge_locked(struct drm_gem_shmem_object *shmem);
+bool drm_gem_shmem_purge(struct drm_gem_shmem_object *shmem);
 
 struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem);
 struct sg_table *drm_gem_shmem_get_pages_sgt(struct drm_gem_shmem_object *shmem);