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

[Christian König <ckoenig.leichtzumerken@xxxxxxxxx>]

Am 12.10.21 um 15:12 schrieb 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.

No, IIRC the Intel guys had fixed that already by adding/removing the 
debugfs file on module load/unload.


Christian.

> 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.Yang@xxxxxxx>
> > ---
> >   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