Re: [PATCH 5/7] dma-buf: rename and cleanup dma_resv_get_list

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 02.06.21 um 22:22 schrieb Jason Ekstrand:
> On Wed, Jun 2, 2021 at 6:17 AM Christian König
> <ckoenig.leichtzumerken@xxxxxxxxx> wrote:
> > When the comment needs to state explicitly that this is doesn't get a reference
> > to the object then the function is named rather badly.
> >
> > Rename the function and use it in even more places.
> >
> > Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> > ---
> >   drivers/dma-buf/dma-resv.c                    | 32 +++++++++----------
> >   .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c  |  2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c   |  2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c      |  2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c       |  2 +-
> >   drivers/gpu/drm/etnaviv/etnaviv_gem.c         |  2 +-
> >   drivers/gpu/drm/i915/gem/i915_gem_busy.c      |  2 +-
> >   drivers/gpu/drm/msm/msm_gem.c                 |  4 +--
> >   drivers/gpu/drm/nouveau/nouveau_fence.c       |  2 +-
> >   drivers/gpu/drm/qxl/qxl_debugfs.c             |  2 +-
> >   drivers/gpu/drm/radeon/radeon_sync.c          |  2 +-
> >   drivers/gpu/drm/ttm/ttm_bo.c                  |  2 +-
> >   include/linux/dma-resv.h                      | 25 +++++++--------
> >   13 files changed, 39 insertions(+), 42 deletions(-)
> >
> > diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> > index 81b032b43457..b1a1a31dc009 100644
> > --- a/drivers/dma-buf/dma-resv.c
> > +++ b/drivers/dma-buf/dma-resv.c
> > @@ -149,8 +149,7 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
> >
> >          dma_resv_assert_held(obj);
> >
> > -       old = dma_resv_get_list(obj);
> > -
> > +       old = dma_resv_shared(obj);
> >          if (old && old->shared_max) {
> >                  if ((old->shared_count + num_fences) <= old->shared_max)
> >                          return 0;
> > @@ -217,12 +216,13 @@ EXPORT_SYMBOL(dma_resv_reserve_shared);
> >    */
> >   void dma_resv_reset_shared_max(struct dma_resv *obj)
> >   {
> > -       /* Test shared fence slot reservation */
> > -       if (rcu_access_pointer(obj->fence)) {
> > -               struct dma_resv_list *fence = dma_resv_get_list(obj);
> > +       struct dma_resv_list *fences = dma_resv_shared(obj);
> >
> > -               fence->shared_max = fence->shared_count;
> > -       }
> > +       dma_resv_assert_held(obj);
> Does it make sense to assert we hold the lock *before* we touch it
> with something that requires that we do?  Maybe it doesn't matter?

As far as I can see that shouldn't matter.

> > +
> > +       /* Test shared fence slot reservation */
> > +       if (fences)
> > +               fences->shared_max = fences->shared_count;
> >   }
> >   #endif
> >
> > @@ -244,7 +244,7 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
> >
> >          dma_resv_assert_held(obj);
> >
> > -       fobj = dma_resv_get_list(obj);
> > +       fobj = dma_resv_shared(obj);
> >          count = fobj->shared_count;
> >
> >          write_seqcount_begin(&obj->seq);
> > @@ -287,7 +287,7 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
> >
> >          dma_resv_assert_held(obj);
> >
> > -       old = dma_resv_get_list(obj);
> > +       old = dma_resv_shared(obj);
> >          if (old)
> >                  i = old->shared_count;
> >
> > @@ -326,7 +326,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> >          dma_resv_assert_held(dst);
> >
> >          rcu_read_lock();
> > -       src_list = rcu_dereference(src->fence);
> > +       src_list = dma_resv_shared(src);
> >
> >   retry:
> >          if (src_list) {
> > @@ -339,7 +339,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> >                          return -ENOMEM;
> >
> >                  rcu_read_lock();
> > -               src_list = rcu_dereference(src->fence);
> > +               src_list = dma_resv_shared(src);
> >                  if (!src_list || src_list->shared_count > shared_count) {
> >                          kfree(dst_list);
> >                          goto retry;
> > @@ -357,7 +357,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> >
> >                          if (!dma_fence_get_rcu(fence)) {
> >                                  dma_resv_list_free(dst_list);
> > -                               src_list = rcu_dereference(src->fence);
> > +                               src_list = dma_resv_shared(src);
> >                                  goto retry;
> >                          }
> >
> > @@ -376,7 +376,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> >          new = dma_fence_get_rcu_safe(&src->fence_excl);
> >          rcu_read_unlock();
> >
> > -       src_list = dma_resv_get_list(dst);
> > +       src_list = dma_resv_shared(dst);
> >          old = dma_resv_exclusive(dst);
> >
> >          write_seqcount_begin(&dst->seq);
> > @@ -429,7 +429,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
> >                  if (fence_excl && !dma_fence_get_rcu(fence_excl))
> >                          goto unlock;
> >
> > -               fobj = rcu_dereference(obj->fence);
> > +               fobj = dma_resv_shared(obj);
> >                  if (fobj)
> >                          sz += sizeof(*shared) * fobj->shared_max;
> >
> > @@ -535,7 +535,7 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
> >          }
> >
> >          if (wait_all) {
> > -               struct dma_resv_list *fobj = rcu_dereference(obj->fence);
> > +               struct dma_resv_list *fobj = dma_resv_shared(obj);
> >
> >                  if (fobj)
> >                          shared_count = fobj->shared_count;
> > @@ -620,7 +620,7 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
> >          seq = read_seqcount_begin(&obj->seq);
> >
> >          if (test_all) {
> > -               struct dma_resv_list *fobj = rcu_dereference(obj->fence);
> > +               struct dma_resv_list *fobj = dma_resv_shared(obj);
> >                  unsigned int i;
> >
> >                  if (fobj)
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > index d5e6519bdea1..e90495ca49fd 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
> > @@ -247,7 +247,7 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo,
> >          if (!ef)
> >                  return -EINVAL;
> >
> > -       old = dma_resv_get_list(resv);
> > +       old = dma_resv_shared(resv);
> >          if (!old)
> >                  return 0;
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> > index 6dd0ea6e9e24..3b13c8a38c4e 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> > @@ -49,7 +49,7 @@ __dma_resv_make_exclusive(struct dma_resv *obj)
> >          unsigned int count;
> >          int r;
> >
> > -       if (!dma_resv_get_list(obj)) /* no shared fences to convert */
> > +       if (!dma_resv_shared(obj)) /* no shared fences to convert */
> >                  return 0;
> >
> >          r = dma_resv_get_fences_rcu(obj, NULL, &count, &fences);
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > index c84d5b843985..c50d9f92a0cd 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > @@ -213,7 +213,7 @@ int amdgpu_sync_resv(struct amdgpu_device *adev, struct amdgpu_sync *sync,
> >          f = dma_resv_exclusive(resv);
> >          r = amdgpu_sync_fence(sync, f);
> >
> > -       flist = dma_resv_get_list(resv);
> > +       flist = dma_resv_shared(resv);
> >          if (!flist || r)
> >                  return r;
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > index 663aa7d2e2ea..ddb6ce7d48bc 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> > @@ -1338,7 +1338,7 @@ static bool amdgpu_ttm_bo_eviction_valuable(struct ttm_buffer_object *bo,
> >           * If true, then return false as any KFD process needs all its BOs to
> >           * be resident to run successfully
> >           */
> > -       flist = dma_resv_get_list(bo->base.resv);
> > +       flist = dma_resv_shared(bo->base.resv);
> >          if (flist) {
> >                  for (i = 0; i < flist->shared_count; ++i) {
> >                          f = rcu_dereference_protected(flist->shared[i],
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > index d4f54dea8ac1..4d43b8630f0e 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > @@ -461,7 +461,7 @@ static void etnaviv_gem_describe(struct drm_gem_object *obj, struct seq_file *m)
> >                          off, etnaviv_obj->vaddr, obj->size);
> >
> >          rcu_read_lock();
> > -       fobj = rcu_dereference(robj->fence);
> > +       fobj = dma_resv_shared(robj);
> >          if (fobj) {
> >                  unsigned int i, shared_count = fobj->shared_count;
> >
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > index 02312a0c3a36..3f94becac541 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> > @@ -116,7 +116,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
> >          args->busy = busy_check_writer(dma_resv_exclusive(obj->base.resv));
> >
> >          /* Translate shared fences to READ set of engines */
> > -       list = rcu_dereference(obj->base.resv->fence);
> > +       list = dma_resv_shared(obj->base.resv);
> >          if (list) {
> >                  unsigned int shared_count = list->shared_count, i;
> >
> > diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> > index 54c1b53426d6..43af91df552e 100644
> > --- a/drivers/gpu/drm/msm/msm_gem.c
> > +++ b/drivers/gpu/drm/msm/msm_gem.c
> > @@ -817,7 +817,7 @@ int msm_gem_sync_object(struct drm_gem_object *obj,
> >          struct dma_fence *fence;
> >          int i, ret;
> >
> > -       fobj = dma_resv_get_list(obj->resv);
> > +       fobj = dma_resv_shared(obj->resv);
> >          if (!fobj || (fobj->shared_count == 0)) {
> >                  fence = dma_resv_exclusive(obj->resv);
> >                  /* don't need to wait on our own fences, since ring is fifo */
> > @@ -1025,7 +1025,7 @@ void msm_gem_describe(struct drm_gem_object *obj, struct seq_file *m,
> >          }
> >
> >          rcu_read_lock();
> > -       fobj = rcu_dereference(robj->fence);
> > +       fobj = dma_resv_shared(robj);
> >          if (fobj) {
> >                  unsigned int i, shared_count = fobj->shared_count;
> >
> > diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
> > index a6cb35181aee..5ce441c655ea 100644
> > --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> > +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> > @@ -355,7 +355,7 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, bool e
> >                          return ret;
> >          }
> >
> > -       fobj = dma_resv_get_list(resv);
> > +       fobj = dma_resv_shared(resv);
> >          fence = dma_resv_exclusive(resv);
> >
> >          if (fence && (!exclusive || !fobj || !fobj->shared_count)) {
> > diff --git a/drivers/gpu/drm/qxl/qxl_debugfs.c b/drivers/gpu/drm/qxl/qxl_debugfs.c
> > index 183d15e2cf58..0acc70a6d3dd 100644
> > --- a/drivers/gpu/drm/qxl/qxl_debugfs.c
> > +++ b/drivers/gpu/drm/qxl/qxl_debugfs.c
> > @@ -61,7 +61,7 @@ qxl_debugfs_buffers_info(struct seq_file *m, void *data)
> >                  int rel;
> >
> >                  rcu_read_lock();
> > -               fobj = rcu_dereference(bo->tbo.base.resv->fence);
> > +               fobj = dma_resv_shared(bo->tbo.base.resv);
> >                  rel = fobj ? fobj->shared_count : 0;
> >                  rcu_read_unlock();
> >
> > diff --git a/drivers/gpu/drm/radeon/radeon_sync.c b/drivers/gpu/drm/radeon/radeon_sync.c
> > index e476f90ef1c1..a9cdb88da173 100644
> > --- a/drivers/gpu/drm/radeon/radeon_sync.c
> > +++ b/drivers/gpu/drm/radeon/radeon_sync.c
> > @@ -105,7 +105,7 @@ int radeon_sync_resv(struct radeon_device *rdev,
> >          else if (f)
> >                  r = dma_fence_wait(f, true);
> >
> > -       flist = dma_resv_get_list(resv);
> > +       flist = dma_resv_shared(resv);
> >          if (shared || !flist || r)
> >                  return r;
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > index 92361556bf0b..c41ef0caa492 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -261,7 +261,7 @@ static void ttm_bo_flush_all_fences(struct ttm_buffer_object *bo)
> >          int i;
> >
> >          rcu_read_lock();
> > -       fobj = rcu_dereference(resv->fence);
> > +       fobj = dma_resv_shared(resv);
> >          fence = dma_resv_exclusive(resv);
> >          if (fence && !fence->ops->signaled)
> >                  dma_fence_enable_sw_signaling(fence);
> > diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> > index 7549ec5eb35c..98ac66fecb71 100644
> > --- a/include/linux/dma-resv.h
> > +++ b/include/linux/dma-resv.h
> > @@ -78,20 +78,6 @@ struct dma_resv {
> >   #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
> >   #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
> >
> > -/**
> > - * dma_resv_get_list - get the reservation object's
> > - * shared fence list, with update-side lock held
> > - * @obj: the reservation object
> > - *
> > - * Returns the shared fence list.  Does NOT take references to
> > - * the fence.  The obj->lock must be held.
> > - */
> > -static inline struct dma_resv_list *dma_resv_get_list(struct dma_resv *obj)
> > -{
> > -       return rcu_dereference_protected(obj->fence,
> > -                                        dma_resv_held(obj));
> > -}
> > -
> >   #ifdef CONFIG_DEBUG_MUTEXES
> >   void dma_resv_reset_shared_max(struct dma_resv *obj);
> >   #else
> > @@ -267,6 +253,17 @@ dma_resv_get_excl_rcu(struct dma_resv *obj)
> >          return fence;
> >   }
> >
> > +/**
> > + * dma_resv_shared - get the reservation object's shared fence list
> > + * @obj: the reservation object
> > + *
> > + * Returns the shared fence list. The obj->lock or rcu read side must be held.
> > + */
> > +static inline struct dma_resv_list *dma_resv_shared(struct dma_resv *obj)
> Maybe dma_resv_shared_list() just to be a little more clear what's
> being returned?

Ok, renamed this one and dma_resv_exclusive into dma_resv_excl_fence as 
well.

Christian.

> --Jason
>
> > +{
> > +       return rcu_dereference_check(obj->fence, dma_resv_held(obj));
> > +}
> > +
> >   void dma_resv_init(struct dma_resv *obj);
> >   void dma_resv_fini(struct dma_resv *obj);
> >   int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences);
> > --
> > 2.25.1