[PATCH v10 3/5] drm/gem/shmem: Export drm_gem_shmem_get_pages_sgt_locked()

[Lyude Paul <lyude@redhat.com>]

We will need this for implementing a set of SGTable bindings in Rust for
gem shmem objects, so that we can use the dma_resv lock to protect
additional resources in the shmem object.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 16 +++++++++++++++-
 include/drm/drm_gem_shmem_helper.h     |  1 +
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index addf8c1e5341e..15de7f6cc4981 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -786,12 +786,25 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_shmem_object *shmem)
 }
 EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
 
-static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
+/**
+ * drm_gem_shmem_get_sg_table - Under dma_resv lock, provide a scatter/gather table of
+ *				pinned pages for an shmem GEM object.
+ * @shmem: shmem GEM object
+ *
+ * This function is the same as drm_gem_shmem_get_pages_sgt, except that the caller is expected to
+ * already hold the dma_resv lock for @shmem.
+ *
+ * Returns:
+ * A poitner to the scatter/gather table of pinned pages, or error pointer on failure.
+ */
+struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem)
 {
 	struct drm_gem_object *obj = &shmem->base;
 	int ret;
 	struct sg_table *sgt;
 
+	dma_resv_assert_held(shmem->base.resv);
+
 	if (shmem->sgt)
 		return shmem->sgt;
 
@@ -822,6 +835,7 @@ static struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_
 	drm_gem_shmem_put_pages_locked(shmem);
 	return ERR_PTR(ret);
 }
+EXPORT_SYMBOL_GPL(drm_gem_shmem_get_pages_sgt_locked);
 
 /**
  * drm_gem_shmem_get_pages_sgt - Pin pages, dma map them, and return a
diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h
index b2c23af628e1a..682207ce9d1b5 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -138,6 +138,7 @@ void drm_gem_shmem_purge_locked(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);
+struct sg_table *drm_gem_shmem_get_pages_sgt_locked(struct drm_gem_shmem_object *shmem);
 
 void drm_gem_shmem_print_info(const struct drm_gem_shmem_object *shmem,
 			      struct drm_printer *p, unsigned int indent);
-- 
2.53.0