[PATCH v15 15/23] drm/shmem-helper: Switch drm_gem_shmem_vmap/vunmap to use pin/unpin

[Dmitry Osipenko]

The vmapped pages shall be pinned in memory and previously get/put_pages()
were implicitly hard-pinning/unpinning the pages. This will no longer be
the case with addition of memory shrinker because pages_use_count > 0 won't
determine anymore whether pages are hard-pinned (they will be soft-pinned),
while the new pages_pin_count will do the hard-pinning. Switch the
vmap/vunmap() to use pin/unpin() functions in a preparation of addition
of the memory shrinker support to drm-shmem.

Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
---
 drivers/gpu/drm/drm_gem_shmem_helper.c | 13 ++++++++++---
 include/drm/drm_gem_shmem_helper.h     |  2 +-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c 
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index f386289c24fc..17a0177acb5d 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -274,6 +274,13 @@ static void drm_gem_shmem_kref_unpin_pages(struct kref 
*kref)
        drm_gem_shmem_put_pages_locked(shmem);
 }
 
+static void drm_gem_shmem_unpin_locked(struct drm_gem_shmem_object *shmem)
+{
+       dma_resv_assert_held(shmem->base.resv);
+
+       kref_put(&shmem->pages_pin_count, drm_gem_shmem_kref_unpin_pages);
+}
+
 /**
  * drm_gem_shmem_pin - Pin backing pages for a shmem GEM object
  * @shmem: shmem GEM object
@@ -357,7 +364,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object 
*shmem,
                        return 0;
                }
 
-               ret = drm_gem_shmem_get_pages_locked(shmem);
+               ret = drm_gem_shmem_pin_locked(shmem);
                if (ret)
                        goto err_zero_use;
 
@@ -380,7 +387,7 @@ int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object 
*shmem,
 
 err_put_pages:
        if (!obj->import_attach)
-               drm_gem_shmem_put_pages_locked(shmem);
+               drm_gem_shmem_unpin_locked(shmem);
 err_zero_use:
        shmem->vmap_use_count = 0;
 
@@ -417,7 +424,7 @@ void drm_gem_shmem_vunmap_locked(struct 
drm_gem_shmem_object *shmem,
                        return;
 
                vunmap(shmem->vaddr);
-               drm_gem_shmem_put_pages_locked(shmem);
+               drm_gem_shmem_unpin_locked(shmem);
        }
 
        shmem->vaddr = NULL;
diff --git a/include/drm/drm_gem_shmem_helper.h 
b/include/drm/drm_gem_shmem_helper.h
index a5a3c193cc8f..400ecd63f45f 100644
--- a/include/drm/drm_gem_shmem_helper.h
+++ b/include/drm/drm_gem_shmem_helper.h
@@ -137,7 +137,7 @@ int drm_gem_shmem_madvise_locked(struct 
drm_gem_shmem_object *shmem, int madv);
 static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object 
*shmem)
 {
        return (shmem->madv > 0) &&
-               !shmem->vmap_use_count && shmem->sgt &&
+               !kref_read(&shmem->pages_pin_count) && shmem->sgt &&
                !shmem->base.dma_buf && !shmem->base.import_attach;
 }
 
-- 
2.41.0