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BUG: KCSAN: data-race in _find_next_bit / ext4_free_inode

write to 0xffff8881042f5300 of 8 bytes by task 1765 on cpu 0:
 instrument_write include/linux/instrumented.h:42 [inline]
 __instrument_read_write_bitop include/asm-generic/bitops/instrumented-non-atomic.h:79 [inline]
 __test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:109 [inline]
 __test_and_clear_bit_le include/asm-generic/bitops/le.h:125 [inline]
 ext4_free_inode+0x5ce/0xa00 fs/ext4/ialloc.c:314
 ext4_evict_inode+0xb7e/0xdb0 fs/ext4/inode.c:333
 evict+0x1c8/0x3c0 fs/inode.c:584
 iput_final fs/inode.c:1660 [inline]
 iput+0x433/0x590 fs/inode.c:1686
 do_unlinkat+0x293/0x4f0 fs/namei.c:4099
 __do_sys_unlink fs/namei.c:4139 [inline]
 __se_sys_unlink fs/namei.c:4137 [inline]
 __x64_sys_unlink+0x2c/0x30 fs/namei.c:4137
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881042f5300 of 8 bytes by task 7141 on cpu 1:
 _find_next_bit+0x4f/0x190 lib/find_bit.c:41
 find_next_zero_bit include/asm-generic/bitops/find.h:94 [inline]
 find_next_zero_bit_le include/asm-generic/bitops/le.h:17 [inline]
 find_inode_bit+0xc8/0x330 fs/ext4/ialloc.c:722
 __ext4_new_inode+0xc7a/0x2f70 fs/ext4/ialloc.c:1063
 ext4_symlink+0x2c3/0x700 fs/ext4/namei.c:3463
 vfs_symlink+0x23a/0x300 fs/namei.c:4172
 do_symlinkat+0xeb/0x280 fs/namei.c:4202
 __do_sys_symlink fs/namei.c:4223 [inline]
 __se_sys_symlink fs/namei.c:4221 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4221
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7141 Comm: syz-executor.0 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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