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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

write to 0xffff8880b332c300 of 4 bytes by task 23507 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:417 [inline]
 __d_instantiate+0x2b0/0x310 fs/dcache.c:1931
 d_instantiate_new+0x76/0x100 fs/dcache.c:1975
 ext4_mkdir+0x5c8/0x850 fs/ext4/namei.c:2821
 vfs_mkdir+0x281/0x3b0 fs/namei.c:3625
 do_mkdirat+0x1b5/0x200 fs/namei.c:3648
 __do_sys_mkdir fs/namei.c:3664 [inline]
 __se_sys_mkdir fs/namei.c:3662 [inline]
 __x64_sys_mkdir+0x3d/0x50 fs/namei.c:3662
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b332c300 of 4 bytes by task 23510 on cpu 1:
 d_revalidate fs/namei.c:753 [inline]
 lookup_fast+0x176/0x3a0 fs/namei.c:1479
 open_last_lookups fs/namei.c:3121 [inline]
 path_openat+0x2ba/0x23d0 fs/namei.c:3343
 do_filp_open+0x11e/0x1b0 fs/namei.c:3373
 do_sys_openat2+0x52e/0x680 fs/open.c:1148
 do_sys_open+0xa2/0x110 fs/open.c:1164
 ksys_open include/linux/syscalls.h:1386 [inline]
 __do_sys_open fs/open.c:1170 [inline]
 __se_sys_open fs/open.c:1168 [inline]
 __x64_sys_open+0x50/0x60 fs/open.c:1168
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23510 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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