drm/msm: deal with exhausted vmap space better

Some, but not all, callers of obj->vmap() would check if return
IS_ERR(). So let's actually return an error if vmap() fails. And fixup
the call-sites that were not handling this properly.

Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/adreno/adreno_gpu.c

···
 	}
 
 	adreno_gpu->memptrs = msm_gem_vaddr(adreno_gpu->memptrs_bo);
-	if (!adreno_gpu->memptrs) {
+	if (IS_ERR(adreno_gpu->memptrs)) {
 		dev_err(drm->dev, "could not vmap memptrs\n");
 		return -ENOMEM;
 	}

drivers/gpu/drm/msm/msm_fbdev.c

···
 	dev->mode_config.fb_base = paddr;
 
 	fbi->screen_base = msm_gem_vaddr_locked(fbdev->bo);
+	if (IS_ERR(fbi->screen_base)) {
+		ret = PTR_ERR(fbi->screen_base);
+		goto fail_unlock;
+	}
 	fbi->screen_size = fbdev->bo->size;
 	fbi->fix.smem_start = paddr;
 	fbi->fix.smem_len = fbdev->bo->size;

drivers/gpu/drm/msm/msm_gem.c

···
 			return ERR_CAST(pages);
 		msm_obj->vaddr = vmap(pages, obj->size >> PAGE_SHIFT,
 				VM_MAP, pgprot_writecombine(PAGE_KERNEL));
+		if (msm_obj->vaddr == NULL)
+			return ERR_PTR(-ENOMEM);
 	}
 	return msm_obj->vaddr;
 }

drivers/gpu/drm/msm/msm_rd.c

···
 		struct msm_gem_object *obj = submit->bos[idx].obj;
 		const char *buf = msm_gem_vaddr_locked(&obj->base);
 
+		if (IS_ERR(buf))
+			continue;
+
 		buf += iova - submit->bos[idx].iova;
 
 		rd_write_section(rd, RD_GPUADDR,

drivers/gpu/drm/msm/msm_ringbuffer.c

···
 	}
 
 	ring->start = msm_gem_vaddr_locked(ring->bo);
+	if (IS_ERR(ring->start)) {
+		ret = PTR_ERR(ring->start);
+		goto fail;
+	}
 	ring->end   = ring->start + (size / 4);
 	ring->cur   = ring->start;