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BUG: KCSAN: data-race in ext4_free_inode / find_next_zero_bit

write to 0xffff888121a99018 of 8 bytes by task 7289 on cpu 0:
 __test_and_clear_bit include/asm-generic/bitops-instrumented.h:213 [inline]
 __test_and_clear_bit_le include/asm-generic/bitops/le.h:95 [inline]
 ext4_free_inode+0x5f1/0xaa0 fs/ext4/ialloc.c:313
 ext4_evict_inode+0x9a9/0xdb0 fs/ext4/inode.c:333
 evict+0x244/0x410 fs/inode.c:574
 iput_final fs/inode.c:1563 [inline]
 iput+0x371/0x4e0 fs/inode.c:1589
 dentry_unlink_inode+0x27a/0x2f0 fs/dcache.c:374
 d_delete fs/dcache.c:2449 [inline]
 d_delete+0xdb/0xe0 fs/dcache.c:2438
 vfs_rmdir fs/namei.c:3884 [inline]
 vfs_rmdir+0x2e2/0x300 fs/namei.c:3849
 do_rmdir+0x2cb/0x300 fs/namei.c:3932
 __do_sys_rmdir fs/namei.c:3950 [inline]
 __se_sys_rmdir fs/namei.c:3948 [inline]
 __x64_sys_rmdir+0x2f/0x40 fs/namei.c:3948
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888121a99018 of 8 bytes by task 7761 on cpu 1:
 _find_next_bit lib/find_bit.c:39 [inline]
 find_next_zero_bit+0x4e/0xe0 lib/find_bit.c:79
 find_next_zero_bit_le include/asm-generic/bitops/le.h:15 [inline]
 find_inode_bit.isra.0+0x82/0x300 fs/ext4/ialloc.c:715
 __ext4_new_inode+0xd4b/0x3070 fs/ext4/ialloc.c:914
 ext4_mkdir+0x289/0x820 fs/ext4/namei.c:2763
 vfs_mkdir+0x283/0x390 fs/namei.c:3807
 do_mkdirat+0x1ac/0x1f0 fs/namei.c:3830
 __do_sys_mkdirat fs/namei.c:3841 [inline]
 __se_sys_mkdirat fs/namei.c:3839 [inline]
 __x64_sys_mkdirat+0x4d/0x60 fs/namei.c:3839
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7761 Comm: syz-executor.0 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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