linux-kernel - [xiang:erofs/advancedpcl 16/16] fs/erofs/zdata.c:896:12: warning: variable 'len' is uninitialized when used here

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Date:   Thu, 14 Jul 2022 16:49:20 +0800
From:   kernel test robot <lkp@...el.com>
To:     Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        Xiang Gao <xiang@...nel.org>, linux-kernel@...r.kernel.org
Subject: [xiang:erofs/advancedpcl 16/16] fs/erofs/zdata.c:896:12: warning:
 variable 'len' is uninitialized when used here

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git erofs/advancedpcl
head:   0889e3f1d4cc1d9cb08d961107c5e810c47ecfd0
commit: 0889e3f1d4cc1d9cb08d961107c5e810c47ecfd0 [16/16] erofs: introduce multi-reference pclusters (fully-referenced)
config: x86_64-randconfig-a005 (https://download.01.org/0day-ci/archive/20220714/202207141642.UPeaIPx7-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 5e61b9c556267086ef9b743a0b57df302eef831b)
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://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git/commit/?id=0889e3f1d4cc1d9cb08d961107c5e810c47ecfd0
        git remote add xiang https://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git
        git fetch --no-tags xiang erofs/advancedpcl
        git checkout 0889e3f1d4cc1d9cb08d961107c5e810c47ecfd0
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash fs/erofs/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> fs/erofs/zdata.c:896:12: warning: variable 'len' is uninitialized when used here [-Wuninitialized]
                                   cur += len;
                                          ^~~
   fs/erofs/zdata.c:887:32: note: initialize the variable 'len' to silence this warning
                           unsigned int pgnr, scur, len;
                                                       ^
                                                        = 0
   1 warning generated.


vim +/len +896 fs/erofs/zdata.c

   869	
   870	static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
   871					      int err)
   872	{
   873		unsigned int off0 = be->pcl->pageofs_out;
   874		struct list_head *p, *n;
   875	
   876		list_for_each_safe(p, n, &be->decompressed_secondary_bvecs) {
   877			struct z_erofs_bvec_item *bvi;
   878			unsigned int end, cur;
   879			void *dst, *src;
   880	
   881			bvi = container_of(p, struct z_erofs_bvec_item, list);
   882			cur = bvi->bvec.offset < 0 ? -bvi->bvec.offset : 0;
   883			end = min_t(unsigned int, be->pcl->length - bvi->bvec.offset,
   884				    bvi->bvec.end);
   885			dst = kmap_local_page(bvi->bvec.page);
   886			while (cur < end) {
   887				unsigned int pgnr, scur, len;
   888	
   889				pgnr = (bvi->bvec.offset + cur + off0) >> PAGE_SHIFT;
   890				DBG_BUGON(pgnr >= be->nr_pages);
   891	
   892				scur = bvi->bvec.offset + cur -
   893						((pgnr << PAGE_SHIFT) - off0);
   894				if (!be->decompressed_pages[pgnr]) {
   895					err = -EFSCORRUPTED;
 > 896					cur += len;
   897					continue;
   898				}
   899				src = kmap_local_page(be->decompressed_pages[pgnr]);
   900				len = min_t(unsigned int, end - cur, PAGE_SIZE - scur);
   901				memcpy(dst + cur, src + scur, len);
   902				kunmap_local(src);
   903				cur += len;
   904			}
   905			kunmap_local(dst);
   906			if (err)
   907				z_erofs_page_mark_eio(bvi->bvec.page);
   908			z_erofs_onlinepage_endio(bvi->bvec.page);
   909			list_del(p);
   910			kfree(bvi);
   911		}
   912	}
   913	

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