Re: [PATCH Review 1/1] drm/ttm: fix debugfs node create failed

[Das, Nirmoy]

On 10/12/2021 1:58 PM, Stanley.Yang wrote:
Test scenario:
     modprobe amdgpu -> rmmod amdgpu -> modprobe amdgpu
Error log:
     [   54.396807] debugfs: File 'page_pool' in directory 'amdttm' already 
present!
     [   54.396833] debugfs: File 'page_pool_shrink' in directory 'amdttm' 
already present!
     [   54.396848] debugfs: File 'buffer_objects' in directory 'amdttm' 
already present!


We should instead add a check if those debugfs files already 
exist/created in ttm debugfs dir using debugfs_lookup() before creating.


Regards,

Nirmoy



Reason:
     page_pool, page_pool_shrink and buffer_objects can be removed when
     rmmod amdttm, in the above test scenario only rmmod amdgpu, so those
     debugfs node will not be removed, this caused file create failed.
Soultion:
     create ttm_page directory under ttm_root directory when insmod amdgpu,
     page_pool, page_pool_shrink and buffer_objects are stored in ttm_page 
directiry,
     remove ttm_page directory when do rmmod amdgpu, this can fix above issue.

Signed-off-by: Stanley.Yang <stanley.y...@amd.com>
---
  drivers/gpu/drm/ttm/ttm_device.c | 12 +++++++++++-
  drivers/gpu/drm/ttm/ttm_module.c |  1 +
  drivers/gpu/drm/ttm/ttm_module.h |  1 +
  drivers/gpu/drm/ttm/ttm_pool.c   |  4 ++--
  4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_device.c b/drivers/gpu/drm/ttm/ttm_device.c
index 1de23edbc182..ad170328f0c8 100644
--- a/drivers/gpu/drm/ttm/ttm_device.c
+++ b/drivers/gpu/drm/ttm/ttm_device.c
@@ -55,6 +55,10 @@ static void ttm_global_release(void)
  
  	ttm_pool_mgr_fini();
  
+#ifdef CONFIG_DEBUG_FS
+       debugfs_remove(ttm_debugfs_page);
+#endif
+
        __free_page(glob->dummy_read_page);
        memset(glob, 0, sizeof(*glob));
  out:
@@ -85,6 +89,10 @@ static int ttm_global_init(void)
                >> PAGE_SHIFT;
        num_dma32 = min(num_dma32, 2UL << (30 - PAGE_SHIFT));
  
+#ifdef CONFIG_DEBUG_FS
+       ttm_debugfs_page = debugfs_create_dir("ttm_page", ttm_debugfs_root);
+#endif
+
        ttm_pool_mgr_init(num_pages);
        ttm_tt_mgr_init(num_pages, num_dma32);
  
@@ -98,8 +106,10 @@ static int ttm_global_init(void)
        INIT_LIST_HEAD(&glob->device_list);
        atomic_set(&glob->bo_count, 0);
  
-	debugfs_create_atomic_t("buffer_objects", 0444, ttm_debugfs_root,
+#ifdef CONFIG_DEBUG_FS
+       debugfs_create_atomic_t("buffer_objects", 0444, ttm_debugfs_page,
                                &glob->bo_count);
+#endif
  out:
        mutex_unlock(&ttm_global_mutex);
        return ret;
diff --git a/drivers/gpu/drm/ttm/ttm_module.c b/drivers/gpu/drm/ttm/ttm_module.c
index 88970a6b8e32..66595e6e7087 100644
--- a/drivers/gpu/drm/ttm/ttm_module.c
+++ b/drivers/gpu/drm/ttm/ttm_module.c
@@ -38,6 +38,7 @@
  #include "ttm_module.h"
  
  struct dentry *ttm_debugfs_root;
+struct dentry *ttm_debugfs_page;
  
  static int __init ttm_init(void)
  {
diff --git a/drivers/gpu/drm/ttm/ttm_module.h b/drivers/gpu/drm/ttm/ttm_module.h
index d7cac5d4b835..6007dc66f44e 100644
--- a/drivers/gpu/drm/ttm/ttm_module.h
+++ b/drivers/gpu/drm/ttm/ttm_module.h
@@ -36,5 +36,6 @@
  struct dentry;
  
  extern struct dentry *ttm_debugfs_root;
+extern struct dentry *ttm_debugfs_page;
  
  #endif /* _TTM_MODULE_H_ */
diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
index 8be7fd7161fd..ecb33daad7b5 100644
--- a/drivers/gpu/drm/ttm/ttm_pool.c
+++ b/drivers/gpu/drm/ttm/ttm_pool.c
@@ -709,9 +709,9 @@ int ttm_pool_mgr_init(unsigned long num_pages)
        }
  
  #ifdef CONFIG_DEBUG_FS
-       debugfs_create_file("page_pool", 0444, ttm_debugfs_root, NULL,
+       debugfs_create_file("page_pool", 0444, ttm_debugfs_page, NULL,
                            &ttm_pool_debugfs_globals_fops);
-       debugfs_create_file("page_pool_shrink", 0400, ttm_debugfs_root, NULL,
+       debugfs_create_file("page_pool_shrink", 0400, ttm_debugfs_page, NULL,
                            &ttm_pool_debugfs_shrink_fops);
  #endif