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BUG: KCSAN: data-race in ext4_free_inode / find_next_zero_bit

write to 0xffff8881239ed3b8 of 8 bytes by task 8820 on cpu 0:
 instrument_write include/linux/instrumented.h:42 [inline]
 __test_and_clear_bit include/asm-generic/bitops/instrumented-non-atomic.h:85 [inline]
 __test_and_clear_bit_le include/asm-generic/bitops/le.h:95 [inline]
 ext4_free_inode+0x574/0x9e0 fs/ext4/ialloc.c:310
 ext4_evict_inode+0xad0/0xbf0 fs/ext4/inode.c:324
 evict+0x19f/0x470 fs/inode.c:576
 iput_final fs/inode.c:1652 [inline]
 iput+0x44a/0x550 fs/inode.c:1678
 dentry_unlink_inode+0x208/0x220 fs/dcache.c:374
 d_delete+0x78/0xa0 fs/dcache.c:2470
 vfs_rmdir+0x298/0x2b0 fs/namei.c:3718
 do_rmdir+0x170/0x320 fs/namei.c:3766
 __do_sys_rmdir fs/namei.c:3784 [inline]
 __se_sys_rmdir fs/namei.c:3782 [inline]
 __x64_sys_rmdir+0x20/0x30 fs/namei.c:3782
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881239ed3b8 of 8 bytes by task 12195 on cpu 1:
 _find_next_bit lib/find_bit.c:39 [inline]
 find_next_zero_bit+0x3a/0xf0 lib/find_bit.c:87
 find_next_zero_bit_le include/asm-generic/bitops/le.h:15 [inline]
 find_inode_bit+0x2f7/0x380 fs/ext4/ialloc.c:718
 __ext4_new_inode+0xc24/0x2f60 fs/ext4/ialloc.c:927
 ext4_symlink+0x351/0x7e0 fs/ext4/namei.c:3303
 vfs_symlink+0x218/0x2f0 fs/namei.c:3953
 do_symlinkat+0xee/0x280 fs/namei.c:3980
 __do_sys_symlink fs/namei.c:3999 [inline]
 __se_sys_symlink fs/namei.c:3997 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:3997
 do_syscall_64+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12195 Comm: syz-executor.0 Not tainted 5.8.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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