With nouveau fixed all ttm-using drives have the correct nesting of
mmap_sem vs dma_resv, and we can just lock the buffer.

Assuming I didn't screw up anything with my audit of course.

v2:
- Dont forget wu_mutex (Christian König)
- Keep the mmap_sem-less wait optimization (Thomas)
- Use _lock_interruptible to be good citizens (Thomas)

Reviewed-by: Christian König <christian.koe...@amd.com>
Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
Cc: Christian Koenig <christian.koe...@amd.com>
Cc: Huang Rui <ray.hu...@amd.com>
Cc: Gerd Hoffmann <kra...@redhat.com>
Cc: "VMware Graphics" <linux-graphics-maintai...@vmware.com>
Cc: Thomas Hellstrom <thellst...@vmware.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c      | 36 -------------------------------
 drivers/gpu/drm/ttm/ttm_bo_util.c |  1 -
 drivers/gpu/drm/ttm/ttm_bo_vm.c   | 18 +++++-----------
 include/drm/ttm/ttm_bo_api.h      |  4 ----
 4 files changed, 5 insertions(+), 54 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 20ff56f27aa4..d1ce5d315d5b 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -162,7 +162,6 @@ static void ttm_bo_release_list(struct kref *list_kref)
        dma_fence_put(bo->moving);
        if (!ttm_bo_uses_embedded_gem_object(bo))
                dma_resv_fini(&bo->base._resv);
-       mutex_destroy(&bo->wu_mutex);
        bo->destroy(bo);
        ttm_mem_global_free(bdev->glob->mem_glob, acc_size);
 }
@@ -1319,7 +1318,6 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
        INIT_LIST_HEAD(&bo->ddestroy);
        INIT_LIST_HEAD(&bo->swap);
        INIT_LIST_HEAD(&bo->io_reserve_lru);
-       mutex_init(&bo->wu_mutex);
        bo->bdev = bdev;
        bo->type = type;
        bo->num_pages = num_pages;
@@ -1954,37 +1952,3 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
                ;
 }
 EXPORT_SYMBOL(ttm_bo_swapout_all);
-
-/**
- * ttm_bo_wait_unreserved - interruptible wait for a buffer object to become
- * unreserved
- *
- * @bo: Pointer to buffer
- */
-int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo)
-{
-       int ret;
-
-       /*
-        * In the absense of a wait_unlocked API,
-        * Use the bo::wu_mutex to avoid triggering livelocks due to
-        * concurrent use of this function. Note that this use of
-        * bo::wu_mutex can go away if we change locking order to
-        * mmap_sem -> bo::reserve.
-        */
-       ret = mutex_lock_interruptible(&bo->wu_mutex);
-       if (unlikely(ret != 0))
-               return -ERESTARTSYS;
-       if (!dma_resv_is_locked(bo->base.resv))
-               goto out_unlock;
-       ret = dma_resv_lock_interruptible(bo->base.resv, NULL);
-       if (ret == -EINTR)
-               ret = -ERESTARTSYS;
-       if (unlikely(ret != 0))
-               goto out_unlock;
-       dma_resv_unlock(bo->base.resv);
-
-out_unlock:
-       mutex_unlock(&bo->wu_mutex);
-       return ret;
-}
diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c 
b/drivers/gpu/drm/ttm/ttm_bo_util.c
index fe81c565e7ef..82ea26a49959 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -508,7 +508,6 @@ static int ttm_buffer_object_transfer(struct 
ttm_buffer_object *bo,
        INIT_LIST_HEAD(&fbo->base.lru);
        INIT_LIST_HEAD(&fbo->base.swap);
        INIT_LIST_HEAD(&fbo->base.io_reserve_lru);
-       mutex_init(&fbo->base.wu_mutex);
        fbo->base.moving = NULL;
        drm_vma_node_reset(&fbo->base.base.vma_node);
        atomic_set(&fbo->base.cpu_writers, 0);
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 76eedb963693..a61a35e57d1c 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -125,30 +125,22 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
                &bdev->man[bo->mem.mem_type];
        struct vm_area_struct cvma;
 
-       /*
-        * Work around locking order reversal in fault / nopfn
-        * between mmap_sem and bo_reserve: Perform a trylock operation
-        * for reserve, and if it fails, retry the fault after waiting
-        * for the buffer to become unreserved.
-        */
        if (unlikely(!dma_resv_trylock(bo->base.resv))) {
                if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
                        if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
                                ttm_bo_get(bo);
                                up_read(&vmf->vma->vm_mm->mmap_sem);
-                               (void) ttm_bo_wait_unreserved(bo);
+                               if (!dma_resv_lock_interruptible(bo->base.resv,
+                                                                NULL))
+                                       dma_resv_unlock(bo->base.resv);
                                ttm_bo_put(bo);
                        }
 
                        return VM_FAULT_RETRY;
                }
 
-               /*
-                * If we'd want to change locking order to
-                * mmap_sem -> bo::reserve, we'd use a blocking reserve here
-                * instead of retrying the fault...
-                */
-               return VM_FAULT_NOPAGE;
+               if (dma_resv_lock_interruptible(bo->base.resv, NULL))
+                       return VM_FAULT_NOPAGE;
        }
 
        /*
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index 43c4929a2171..21c7d0d28757 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -155,7 +155,6 @@ struct ttm_tt;
  * @offset: The current GPU offset, which can have different meanings
  * depending on the memory type. For SYSTEM type memory, it should be 0.
  * @cur_placement: Hint of current placement.
- * @wu_mutex: Wait unreserved mutex.
  *
  * Base class for TTM buffer object, that deals with data placement and CPU
  * mappings. GPU mappings are really up to the driver, but for simpler GPUs
@@ -229,8 +228,6 @@ struct ttm_buffer_object {
        uint64_t offset; /* GPU address space is independent of CPU word size */
 
        struct sg_table *sg;
-
-       struct mutex wu_mutex;
 };
 
 /**
@@ -765,7 +762,6 @@ ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file 
*filp,
 int ttm_bo_swapout(struct ttm_bo_global *glob,
                        struct ttm_operation_ctx *ctx);
 void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
-int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo);
 
 /**
  * ttm_bo_uses_embedded_gem_object - check if the given bo uses the
-- 
2.23.0.rc1

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