Re: [PATCH v4 1/3] md: Move sb writer loop to its own function

[Jonathan Derrick <jonathan.derrick@linux.dev>]

On 2/24/2023 12:23 AM, kernel test robot wrote:
> Hi Jonathan,
> 
> Thank you for the patch! Perhaps something to improve:
> 
> [auto build test WARNING on song-md/md-next]
> [also build test WARNING on linus/master v6.2 next-20230224]
> [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/Jonathan-Derrick/md-Move-sb-writer-loop-to-its-own-function/20230224-035451
> base:   git://git.kernel.org/pub/scm/linux/kernel/git/song/md.git md-next
> patch link:    https://lore.kernel.org/r/20230223195225.534-2-jonathan.derrick%40linux.dev
> patch subject: [PATCH v4 1/3] md: Move sb writer loop to its own function
> config: s390-randconfig-r036-20230223 (https://download.01.org/0day-ci/archive/20230224/202302241507.7JQRJLLW-lkp@intel.com/config)
> compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project db89896bbbd2251fff457699635acbbedeead27f)
> 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
>         # install s390 cross compiling tool for clang build
>         # apt-get install binutils-s390x-linux-gnu
>         # https://github.com/intel-lab-lkp/linux/commit/93818e631c76938f9a3ad87d1baf681645d02ba7
>         git remote add linux-review https://github.com/intel-lab-lkp/linux
>         git fetch --no-tags linux-review Jonathan-Derrick/md-Move-sb-writer-loop-to-its-own-function/20230224-035451
>         git checkout 93818e631c76938f9a3ad87d1baf681645d02ba7
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 olddefconfig
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Link: https://lore.kernel.org/oe-kbuild-all/202302241507.7JQRJLLW-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
>    In file included from drivers/md/md-bitmap.c:31:
>    In file included from include/trace/events/block.h:8:
>    In file included from include/linux/blktrace_api.h:5:
>    In file included from include/linux/blk-mq.h:8:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:75:
>    include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __raw_readb(PCI_IOBASE + addr);
>                              ~~~~~~~~~~ ^
>    include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
>                                                            ~~~~~~~~~~ ^
>    include/uapi/linux/byteorder/big_endian.h:37:59: note: expanded from macro '__le16_to_cpu'
>    #define __le16_to_cpu(x) __swab16((__force __u16)(__le16)(x))
>                                                              ^
>    include/uapi/linux/swab.h:102:54: note: expanded from macro '__swab16'
>    #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
>                                                         ^
>    In file included from drivers/md/md-bitmap.c:31:
>    In file included from include/trace/events/block.h:8:
>    In file included from include/linux/blktrace_api.h:5:
>    In file included from include/linux/blk-mq.h:8:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:75:
>    include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
>                                                            ~~~~~~~~~~ ^
>    include/uapi/linux/byteorder/big_endian.h:35:59: note: expanded from macro '__le32_to_cpu'
>    #define __le32_to_cpu(x) __swab32((__force __u32)(__le32)(x))
>                                                              ^
>    include/uapi/linux/swab.h:115:54: note: expanded from macro '__swab32'
>    #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
>                                                         ^
>    In file included from drivers/md/md-bitmap.c:31:
>    In file included from include/trace/events/block.h:8:
>    In file included from include/linux/blktrace_api.h:5:
>    In file included from include/linux/blk-mq.h:8:
>    In file included from include/linux/scatterlist.h:9:
>    In file included from arch/s390/include/asm/io.h:75:
>    include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writeb(value, PCI_IOBASE + addr);
>                                ~~~~~~~~~~ ^
>    include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
>                                                          ~~~~~~~~~~ ^
>    include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
>                                                          ~~~~~~~~~~ ^
>    include/asm-generic/io.h:692:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsb(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:700:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsw(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:708:20: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            readsl(PCI_IOBASE + addr, buffer, count);
>                   ~~~~~~~~~~ ^
>    include/asm-generic/io.h:717:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesb(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
>    include/asm-generic/io.h:726:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesw(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
>    include/asm-generic/io.h:735:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
>            writesl(PCI_IOBASE + addr, buffer, count);
>                    ~~~~~~~~~~ ^
>>> drivers/md/md-bitmap.c:273:18: warning: variable 'rdev' is used uninitialized whenever function 'write_sb_page' is called [-Wsometimes-uninitialized]
>            struct md_rdev *rdev;
>            ~~~~~~~~~~~~~~~~^~~~
>    drivers/md/md-bitmap.c:278:35: note: uninitialized use occurs here
>                    while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
>                                                    ^~~~
>    drivers/md/md-bitmap.c:273:22: note: initialize the variable 'rdev' to silence this warning
Oops, I missed the rdev = NULL;
V5 incoming

>            struct md_rdev *rdev;
>                                ^
>                                 = NULL
>    13 warnings generated.
> 
> 
> vim +273 drivers/md/md-bitmap.c
> 
>    270	
>    271	static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
>    272	{
>  > 273		struct md_rdev *rdev;
>    274		struct mddev *mddev = bitmap->mddev;
>    275		int ret;
>    276	
>    277		do {
>    278			while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
>    279				ret = __write_sb_page(rdev, bitmap, page);
>    280				if (ret)
>    281					return ret;
>    282			}
>    283		} while (wait && md_super_wait(mddev) < 0);
>    284	
>    285		return 0;
>    286	}
>    287	
>