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BUG: KCSAN: data-race in __dentry_kill / lookup_fast

write to 0xffff8880973b9840 of 4 bytes by task 22763 on cpu 1:
 dentry_unlist fs/dcache.c:519 [inline]
 __dentry_kill+0x147/0x450 fs/dcache.c:575
 dentry_kill fs/dcache.c:692 [inline]
 dput+0x208/0x420 fs/dcache.c:878
 do_unlinkat+0x298/0x4d0 fs/namei.c:3898
 __do_sys_unlink fs/namei.c:3942 [inline]
 __se_sys_unlink fs/namei.c:3940 [inline]
 __x64_sys_unlink+0x2c/0x30 fs/namei.c:3940
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880973b9840 of 4 bytes by task 5072 on cpu 0:
 d_revalidate fs/namei.c:767 [inline]
 lookup_fast+0x15f/0x370 fs/namei.c:1493
 walk_component+0x5c/0x350 fs/namei.c:1856
 lookup_last fs/namei.c:2309 [inline]
 path_lookupat+0x12d/0x560 fs/namei.c:2333
 filename_lookup+0xf2/0x380 fs/namei.c:2366
 user_path_at_empty+0x3b/0x50 fs/namei.c:2646
 do_readlinkat+0x87/0x200 fs/stat.c:419
 __do_sys_readlink fs/stat.c:452 [inline]
 __se_sys_readlink fs/stat.c:449 [inline]
 __x64_sys_readlink+0x43/0x50 fs/stat.c:449
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5072 Comm: systemd-udevd Not tainted 5.9.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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