Re: [PATCH v3] fs/btrfs: Fix uninitialized variable

From: kernel test robot
Date: Tue Apr 20 2021 - 20:07:47 EST

Hi Khaled,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on kdave/for-next]
[also build test WARNING on v5.12-rc8 next-20210420]
[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/Khaled-ROMDHANI/fs-btrfs-Fix-uninitialized-variable/20210420-231754
base: https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next
config: s390-randconfig-r032-20210420 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project ca8eef7e3da8f750d7c7aa004fe426d1d34787ea)
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/0day-ci/linux/commit/c05b2a58c9ed11bd753f1e64695bd89da715fbaa
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Khaled-ROMDHANI/fs-btrfs-Fix-uninitialized-variable/20210420-231754
git checkout c05b2a58c9ed11bd753f1e64695bd89da715fbaa
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=s390

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

All warnings (new ones prefixed by >>):

In file included from fs/btrfs/zoned.c:5:
In file included from include/linux/blkdev.h:26:
In file included from include/linux/scatterlist.h:9:
In file included from arch/s390/include/asm/io.h:80:
include/asm-generic/io.h:464:31: 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:477:61: 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:36:59: 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 fs/btrfs/zoned.c:5:
In file included from include/linux/blkdev.h:26:
In file included from include/linux/scatterlist.h:9:
In file included from arch/s390/include/asm/io.h:80:
include/asm-generic/io.h:490:61: 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:34:59: 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 fs/btrfs/zoned.c:5:
In file included from include/linux/blkdev.h:26:
In file included from include/linux/scatterlist.h:9:
In file included from arch/s390/include/asm/io.h:80:
include/asm-generic/io.h:501:33: 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:511:59: 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:521:59: 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:609:20: 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:617:20: 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:625:20: 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:634:21: 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:643:21: 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:652:21: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
writesl(PCI_IOBASE + addr, buffer, count);
~~~~~~~~~~ ^
>> fs/btrfs/zoned.c:147:10: warning: variable 'zone' is uninitialized when used here [-Wuninitialized]
ASSERT(zone);
^~~~
fs/btrfs/ctree.h:3420:10: note: expanded from macro 'ASSERT'
(likely(expr) ? (void)0 : assertfail(#expr, __FILE__, __LINE__))
^~~~
include/linux/compiler.h:45:39: note: expanded from macro 'likely'
# define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
^
include/linux/compiler.h:33:34: note: expanded from macro '__branch_check__'
______r = __builtin_expect(!!(x), expect); \
^
fs/btrfs/zoned.c:139:10: note: initialize the variable 'zone' to silence this warning
u64 zone;
^
= 0
13 warnings generated.


vim +/zone +147 fs/btrfs/zoned.c

133
134 /*
135 * Get the first zone number of the superblock mirror
136 */
137 static inline u32 sb_zone_number(int shift, int mirror)
138 {
139 u64 zone;
140
141 ASSERT(mirror < BTRFS_SUPER_MIRROR_MAX);
142 switch (mirror) {
143 case 0: zone = 0; break;
144 case 1: zone = 1ULL << (BTRFS_SB_LOG_FIRST_SHIFT - shift); break;
145 case 2: zone = 1ULL << (BTRFS_SB_LOG_SECOND_SHIFT - shift); break;
146 default:
> 147 ASSERT(zone);
148 break;
149 }
150
151 ASSERT(zone <= U32_MAX);
152
153 return (u32)zone;
154 }
155

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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