tree:   https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git fscache-iter-2
head:   23676c28d1a9add6ea09f19ca89b71be994a4b79
commit: b5cd0254309847abfb2eebfbcbd4415d61c5af1b [2/67] fscache: Implement a fallback I/O interface to replace the old API
config: i386-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit/?id=b5cd0254309847abfb2eebfbcbd4415d61c5af1b
        git remote add dhowells-fs https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git
        git fetch --no-tags dhowells-fs fscache-iter-2
        git checkout b5cd0254309847abfb2eebfbcbd4415d61c5af1b
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

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

All errors (new ones prefixed by >>):

>> fs/fscache/io.c:164:5: error: no previous prototype for '__fscache_fallback_read_page' [-Werror=missing-prototypes]
     164 | int __fscache_fallback_read_page(struct fscache_cookie *cookie, struct page *page)
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> fs/fscache/io.c:194:5: error: no previous prototype for '__fscache_fallback_write_page' [-Werror=missing-prototypes]
     194 | int __fscache_fallback_write_page(struct fscache_cookie *cookie, struct page *page)
         |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/fscache/io.c: In function '__fscache_fallback_write_page':
>> fs/fscache/io.c:200:9: error: variable 'len' set but not used [-Werror=unused-but-set-variable]
     200 |  size_t len;
         |         ^~~
>> fs/fscache/io.c:199:9: error: variable 'start' set but not used [-Werror=unused-but-set-variable]
     199 |  loff_t start;
         |         ^~~~~
   cc1: all warnings being treated as errors


vim +/__fscache_fallback_read_page +164 fs/fscache/io.c

   160	
   161	/*
   162	 * Fallback page reading interface.
   163	 */
 > 164	int __fscache_fallback_read_page(struct fscache_cookie *cookie, struct page *page)
   165	{
   166		struct netfs_cache_resources cres;
   167		struct iov_iter iter;
   168		struct bio_vec bvec[1];
   169		int ret;
   170	
   171		_enter("%lx", page->index);
   172	
   173		memset(&cres, 0, sizeof(cres));
   174		bvec[0].bv_page		= page;
   175		bvec[0].bv_offset	= 0;
   176		bvec[0].bv_len		= PAGE_SIZE;
   177		iov_iter_bvec(&iter, READ, bvec, ARRAY_SIZE(bvec), PAGE_SIZE);
   178	
   179		ret = fscache_begin_read_operation(&cres, cookie);
   180		if (ret < 0)
   181			return ret;
   182	
   183		ret = fscache_read(&cres, page_offset(page), &iter, NETFS_READ_HOLE_FAIL,
   184				   NULL, NULL);
   185		fscache_end_operation(&cres);
   186		_leave(" = %d", ret);
   187		return ret;
   188	}
   189	EXPORT_SYMBOL(__fscache_fallback_read_page);
   190	
   191	/*
   192	 * Fallback page writing interface.
   193	 */
 > 194	int __fscache_fallback_write_page(struct fscache_cookie *cookie, struct page *page)
   195	{
   196		struct netfs_cache_resources cres;
   197		struct iov_iter iter;
   198		struct bio_vec bvec[1];
 > 199		loff_t start;
 > 200		size_t len;

---
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