Re: [PATCH v10 9/9] fsdax: set a CoW flag when associate reflink mappings

[kernel test robot <yujie.liu@intel.com>]

Hi Shiyang,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linux/master]
[also build test WARNING on linus/master v5.17-rc1]
[cannot apply to xfs-linux/for-next hnaz-mm/master next-20220128]
[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]

url:    https://github.com/0day-ci/linux/commits/Shiyang-Ruan/fsdax-introduce-fs-query-to-support-reflink/20220127-204239
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2c271fe77d52a0555161926c232cd5bc07178b39
config: x86_64-randconfig-c007-20220124 (https://download.01.org/0day-ci/archive/20220129/202201290206.TU7AHhWg-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project f32dccb9a43b02ce4e540d6ba5dbbdb188f2dc7d)
reproduce (this is a W=1 build):
         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
         chmod +x ~/bin/make.cross
         # https://github.com/0day-ci/linux/commit/26822296a70d211de3c5f4ef903d4c4cf29179bd
         git remote add linux-review https://github.com/0day-ci/linux
         git fetch --no-tags linux-review Shiyang-Ruan/fsdax-introduce-fs-query-to-support-reflink/20220127-204239
         git checkout 26822296a70d211de3c5f4ef903d4c4cf29179bd
         # save the config file to linux build tree
         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 clang-analyzer

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


clang-analyzer warnings: (new ones prefixed by >>)

 >> fs/dax.c:339:2: warning: Value stored to 'mapping' is never read [clang-analyzer-deadcode.DeadStores]
            mapping = (struct address_space *)PAGE_MAPPING_DAX_COW;
            ^         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

vim +/mapping +339 fs/dax.c

d2c997c0f14535 Dan Williams   2017-12-22  328
d2c997c0f14535 Dan Williams   2017-12-22  329  /*
d2c997c0f14535 Dan Williams   2017-12-22  330   * Iterate through all mapped pfns represented by an entry, i.e. skip
d2c997c0f14535 Dan Williams   2017-12-22  331   * 'empty' and 'zero' entries.
d2c997c0f14535 Dan Williams   2017-12-22  332   */
d2c997c0f14535 Dan Williams   2017-12-22  333  #define for_each_mapped_pfn(entry, pfn) \
a77d19f46a37c0 Matthew Wilcox 2018-03-27  334  	for (pfn = dax_to_pfn(entry); \
a77d19f46a37c0 Matthew Wilcox 2018-03-27  335  			pfn < dax_end_pfn(entry); pfn++)
d2c997c0f14535 Dan Williams   2017-12-22  336
26822296a70d21 Shiyang Ruan   2022-01-27  337  static inline void dax_mapping_set_cow_flag(struct address_space *mapping)
26822296a70d21 Shiyang Ruan   2022-01-27  338  {
26822296a70d21 Shiyang Ruan   2022-01-27 @339  	mapping = (struct address_space *)PAGE_MAPPING_DAX_COW;
26822296a70d21 Shiyang Ruan   2022-01-27  340  }
26822296a70d21 Shiyang Ruan   2022-01-27  341

---
0-DAY CI Kernel Test Service, Intel Corporation
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