[android-common:android12-5.10-2022-10 21714/21865] drivers/dma-buf/dma-buf-sysfs-stats.c:142:2: error: static assertion failed due to requirement 'sizeof(struct kobject) >= sizeof(struct work_struct)': kobject is smaller than work_struct

[kernel test robot <lkp@intel.com>]

Hi Mercier,

FYI, the error/warning still remains.

tree:   https://android.googlesource.com/kernel/common android12-5.10-2022-10
head:   987d4745ed78ca0f958513bab62fa9de303f2676
commit: d34064cf6258cb4980ac890e00c3f5e75066d905 [21714/21865] BACKPORT: ANDROID: dma-buf: Move sysfs work out of DMA-BUF export path
config: x86_64-buildonly-randconfig-r002-20230708 (https://download.01.org/0day-ci/archive/20230708/202307080710.bfva0ZXb-lkp@intel.com/config)
compiler: clang version 15.0.7 (https://github.com/llvm/llvm-project.git 8dfdcc7b7bf66834a761bd8de445840ef68e4d1a)
reproduce: (https://download.01.org/0day-ci/archive/20230708/202307080710.bfva0ZXb-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202307080710.bfva0ZXb-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/dma-buf/dma-buf-sysfs-stats.c:142:2: error: static assertion failed due to requirement 'sizeof(struct kobject) >= sizeof(struct work_struct)': kobject is smaller than work_struct
           _Static_assert(sizeof(struct kobject) >= sizeof(struct work_struct),
           ^              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 error generated.


vim +142 drivers/dma-buf/dma-buf-sysfs-stats.c

   138	
   139	static void sysfs_add_workfn(struct work_struct *work)
   140	{
   141		/* The ABI would have to change for this to be false, but let's be paranoid. */
 > 142		_Static_assert(sizeof(struct kobject) >= sizeof(struct work_struct),
   143			"kobject is smaller than work_struct");
   144	
   145		struct dma_buf_sysfs_entry *sysfs_entry =
   146			container_of((struct kobject *)work, struct dma_buf_sysfs_entry, kobj);
   147		struct dma_buf *dmabuf = sysfs_entry->dmabuf;
   148	
   149		/*
   150		 * A dmabuf is ref-counted via its file member. If this handler holds the only
   151		 * reference to the dmabuf, there is no need for sysfs kobject creation. This is an
   152		 * optimization and a race; when the reference count drops to 1 immediately after
   153		 * this check it is not harmful as the sysfs entry will still get cleaned up in
   154		 * dma_buf_stats_teardown, which won't get called until the final dmabuf reference
   155		 * is released, and that can't happen until the end of this function.
   156		 */
   157		if (file_count(dmabuf->file) > 1) {
   158			/*
   159			 * kobject_init_and_add expects kobject to be zero-filled, but we have populated it
   160			 * to trigger this work function.
   161			 */
   162			memset(&dmabuf->sysfs_entry->kobj, 0, sizeof(dmabuf->sysfs_entry->kobj));
   163			dmabuf->sysfs_entry->kobj.kset = dma_buf_per_buffer_stats_kset;
   164			if (kobject_init_and_add(&dmabuf->sysfs_entry->kobj, &dma_buf_ktype, NULL,
   165							"%lu", file_inode(dmabuf->file)->i_ino)) {
   166				kobject_put(&dmabuf->sysfs_entry->kobj);
   167				dmabuf->sysfs_entry = NULL;
   168			}
   169		} else {
   170			/*
   171			 * Free the sysfs_entry and reset the pointer so dma_buf_stats_teardown doesn't
   172			 * attempt to operate on it.
   173			 */
   174			kfree(dmabuf->sysfs_entry);
   175			dmabuf->sysfs_entry = NULL;
   176		}
   177		dma_buf_put(dmabuf);
   178	}
   179	

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