Re: [PATCH] swiotlb: avoid double copy with swiotlb on tx socket

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

Hi Luigi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on linus/master v7.1 next-20260615]
[cannot apply to driver-core/driver-core-testing driver-core/driver-core-next driver-core/driver-core-linus]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Luigi-Rizzo/swiotlb-avoid-double-copy-with-swiotlb-on-tx-socket/20260616-074655
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20260615234220.3946885-1-lrizzo%40google.com
patch subject: [PATCH] swiotlb: avoid double copy with swiotlb on tx socket
config: arm-randconfig-r122-20260616 (https://download.01.org/0day-ci/archive/20260616/202606161921.OPkgBApm-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 16.1.0
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260616/202606161921.OPkgBApm-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/202606161921.OPkgBApm-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   kernel/dma/swiotlb.c: note: in included file (through include/linux/dma-direct.h):
>> include/linux/swiotlb.h:229:65: sparse: sparse: Using plain integer as NULL pointer
>> include/linux/swiotlb.h:229:65: sparse: sparse: Using plain integer as NULL pointer

vim +229 include/linux/swiotlb.h

   224	
   225	static inline bool is_zerocopy_swiotlb_folio(struct page *page)
   226	{
   227		struct folio *folio = page_folio(page);
   228	
 > 229		return folio_test_zcswiotlb(folio) && folio->private != 0;
   230	}
   231	

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