tree: https://github.com/goldwynr/linux btrfs-inode-lock head: 5fa699884bb1683e98e07bc73d2dd9c0f219742c commit: 2dec6d472f199ebac0023fd8f9275aaba80bbe19 [10/15] btrfs: Push inode locking and unlocking into buffered/direct write config: x86_64-randconfig-a002-20200921 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project 4e8c028158b56d9c2142a62464e8e0686bde3584) 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 x86_64 cross compiling tool for clang build # apt-get install binutils-x86-64-linux-gnu git checkout 2dec6d472f199ebac0023fd8f9275aaba80bbe19 # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): return num_written ? num_written : err; ^~~ fs/btrfs/file.c:2075:13: note: initialize the variable 'err' to silence this warning ssize_t err; ^ = 0 1 warning generated. # https://github.com/goldwynr/linux/commit/2dec6d472f199ebac0023fd8f9275aab... git remote add goldwynr https://github.com/goldwynr/linux git fetch --no-tags goldwynr btrfs-inode-lock git checkout 2dec6d472f199ebac0023fd8f9275aaba80bbe19 vim +/err +2147 fs/btrfs/file.c d0215f3e5ebb58 Josef Bacik 2011-01-25 2065 b30ac0fc410970 Al Viro 2014-04-03 2066 static ssize_t btrfs_file_write_iter(struct kiocb *iocb, b30ac0fc410970 Al Viro 2014-04-03 2067 struct iov_iter *from) d0215f3e5ebb58 Josef Bacik 2011-01-25 2068 { d0215f3e5ebb58 Josef Bacik 2011-01-25 2069 struct file *file = iocb->ki_filp; 496ad9aa8ef448 Al Viro 2013-01-23 2070 struct inode *inode = file_inode(file); 0b246afa62b0cf Jeff Mahoney 2016-06-22 2071 struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); d0215f3e5ebb58 Josef Bacik 2011-01-25 2072 struct btrfs_root *root = BTRFS_I(inode)->root; d0215f3e5ebb58 Josef Bacik 2011-01-25 2073 ssize_t num_written = 0; f50cb7aff96459 Omar Sandoval 2019-08-15 2074 const bool sync = iocb->ki_flags & IOCB_DSYNC; 3309dd04cbcd2c Al Viro 2015-04-09 2075 ssize_t err; d0215f3e5ebb58 Josef Bacik 2011-01-25 2076 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2077 /* 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2078 * If BTRFS flips readonly due to some impossible error 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2079 * (fs_info->fs_state now has BTRFS_SUPER_FLAG_ERROR), 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2080 * although we have opened a file as writable, we have 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2081 * to stop this write operation to ensure FS consistency. 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2082 */ 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2083 if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2084 return -EROFS; 5565d30dbf72ae Goldwyn Rodrigues 2020-09-16 2085 91f9943e1c7b66 Christoph Hellwig 2017-08-29 2086 if (!(iocb->ki_flags & IOCB_DIRECT) && 91f9943e1c7b66 Christoph Hellwig 2017-08-29 2087 (iocb->ki_flags & IOCB_NOWAIT)) 91f9943e1c7b66 Christoph Hellwig 2017-08-29 2088 return -EOPNOTSUPP; 91f9943e1c7b66 Christoph Hellwig 2017-08-29 2089 b812ce28796f74 Josef Bacik 2012-11-16 2090 if (sync) b812ce28796f74 Josef Bacik 2012-11-16 2091 atomic_inc(&BTRFS_I(inode)->sync_writers); b812ce28796f74 Josef Bacik 2012-11-16 2092 2ba48ce513c4e5 Al Viro 2015-04-09 2093 if (iocb->ki_flags & IOCB_DIRECT) { 09745ff88d9353 Josef Bacik 2020-09-03 2094 /* 09745ff88d9353 Josef Bacik 2020-09-03 2095 * 1. We must always clear IOCB_DSYNC in order to not deadlock 09745ff88d9353 Josef Bacik 2020-09-03 2096 * in iomap, as it calls generic_write_sync() in this case. 09745ff88d9353 Josef Bacik 2020-09-03 2097 * 2. If we are async, we can call iomap_dio_complete() either 09745ff88d9353 Josef Bacik 2020-09-03 2098 * in 09745ff88d9353 Josef Bacik 2020-09-03 2099 * 09745ff88d9353 Josef Bacik 2020-09-03 2100 * 2.1. A worker thread from the last bio completed. In this 09745ff88d9353 Josef Bacik 2020-09-03 2101 * case we need to mark the btrfs_dio_data that it is 09745ff88d9353 Josef Bacik 2020-09-03 2102 * async in order to call generic_write_sync() properly. 09745ff88d9353 Josef Bacik 2020-09-03 2103 * This is handled by setting BTRFS_DIO_SYNC_STUB in the 09745ff88d9353 Josef Bacik 2020-09-03 2104 * current->journal_info. 09745ff88d9353 Josef Bacik 2020-09-03 2105 * 2.2 The submitter context, because all IO completed 09745ff88d9353 Josef Bacik 2020-09-03 2106 * before we exited iomap_dio_rw(). In this case we can 09745ff88d9353 Josef Bacik 2020-09-03 2107 * just re-set the IOCB_DSYNC on the iocb and we'll do 09745ff88d9353 Josef Bacik 2020-09-03 2108 * the sync below. If our ->end_io() gets called and 09745ff88d9353 Josef Bacik 2020-09-03 2109 * current->journal_info is set, then we know we're in 09745ff88d9353 Josef Bacik 2020-09-03 2110 * our current context and we will clear 09745ff88d9353 Josef Bacik 2020-09-03 2111 * current->journal_info to indicate that we need to 09745ff88d9353 Josef Bacik 2020-09-03 2112 * sync below. 09745ff88d9353 Josef Bacik 2020-09-03 2113 */ 09745ff88d9353 Josef Bacik 2020-09-03 2114 if (sync) { 09745ff88d9353 Josef Bacik 2020-09-03 2115 ASSERT(current->journal_info == NULL); 09745ff88d9353 Josef Bacik 2020-09-03 2116 iocb->ki_flags &= ~IOCB_DSYNC; 09745ff88d9353 Josef Bacik 2020-09-03 2117 current->journal_info = BTRFS_DIO_SYNC_STUB; 09745ff88d9353 Josef Bacik 2020-09-03 2118 } 27fa676c4d30aa Goldwyn Rodrigues 2020-09-16 2119 num_written = btrfs_direct_write(iocb, from); 09745ff88d9353 Josef Bacik 2020-09-03 2120 09745ff88d9353 Josef Bacik 2020-09-03 2121 /* 09745ff88d9353 Josef Bacik 2020-09-03 2122 * As stated above, we cleared journal_info, so we need to do 09745ff88d9353 Josef Bacik 2020-09-03 2123 * the sync ourselves. 09745ff88d9353 Josef Bacik 2020-09-03 2124 */ 09745ff88d9353 Josef Bacik 2020-09-03 2125 if (sync && current->journal_info == NULL) 09745ff88d9353 Josef Bacik 2020-09-03 2126 iocb->ki_flags |= IOCB_DSYNC; 09745ff88d9353 Josef Bacik 2020-09-03 2127 current->journal_info = NULL; d0215f3e5ebb58 Josef Bacik 2011-01-25 2128 } else { e4af400a9c5081 Goldwyn Rodrigues 2018-06-17 2129 num_written = btrfs_buffered_write(iocb, from); d0215f3e5ebb58 Josef Bacik 2011-01-25 2130 } d0215f3e5ebb58 Josef Bacik 2011-01-25 2131 5a3f23d515a2eb Chris Mason 2009-03-31 2132 /* 6c760c072403f4 Josef Bacik 2012-11-09 2133 * We also have to set last_sub_trans to the current log transid, 6c760c072403f4 Josef Bacik 2012-11-09 2134 * otherwise subsequent syncs to a file that's been synced in this bb7ab3b92e46da Adam Buchbinder 2016-03-04 2135 * transaction will appear to have already occurred. 5a3f23d515a2eb Chris Mason 2009-03-31 2136 */ 2f2ff0ee5e4303 Filipe Manana 2015-03-20 2137 spin_lock(&BTRFS_I(inode)->lock); 6c760c072403f4 Josef Bacik 2012-11-09 2138 BTRFS_I(inode)->last_sub_trans = root->log_transid; 2f2ff0ee5e4303 Filipe Manana 2015-03-20 2139 spin_unlock(&BTRFS_I(inode)->lock); e259221763a404 Christoph Hellwig 2016-04-07 2140 if (num_written > 0) e259221763a404 Christoph Hellwig 2016-04-07 2141 num_written = generic_write_sync(iocb, num_written); 0a3404dcff29a7 Miao Xie 2013-01-28 2142 b812ce28796f74 Josef Bacik 2012-11-16 2143 if (sync) b812ce28796f74 Josef Bacik 2012-11-16 2144 atomic_dec(&BTRFS_I(inode)->sync_writers); 26ec73db06b185 Goldwyn Rodrigues 2020-09-16 2145 39279cc3d2704c Chris Mason 2007-06-12 2146 current->backing_dev_info = NULL; 39279cc3d2704c Chris Mason 2007-06-12 @2147 return num_written ? num_written : err; 39279cc3d2704c Chris Mason 2007-06-12 2148 } 39279cc3d2704c Chris Mason 2007-06-12 2149 :::::: The code at line 2147 was first introduced by commit :::::: 39279cc3d2704cfbf9c35dcb5bdd392159ae4625 Btrfs: split up super.c :::::: TO: Chris Mason <chris.mason(a)oracle.com&gt; :::::: CC: David Woodhouse <dwmw2(a)hera.kernel.org&gt; --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org