syzbot

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BUG: KCSAN: data-race in d_delete / lookup_fast

read-write to 0xffff88800901a480 of 4 bytes by task 14900 on cpu 1:
 d_delete+0x66/0xa0 fs/dcache.c:2469
 vfs_unlink+0x38f/0x3b0 fs/namei.c:3847
 do_unlinkat+0x28a/0x4d0 fs/namei.c:3897
 __do_sys_unlink fs/namei.c:3943 [inline]
 __se_sys_unlink fs/namei.c:3941 [inline]
 __x64_sys_unlink+0x2c/0x30 fs/namei.c:3941
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800901a480 of 4 bytes by task 4894 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:1857
 lookup_last fs/namei.c:2310 [inline]
 path_lookupat+0x11d/0x550 fs/namei.c:2334
 filename_lookup+0xf2/0x380 fs/namei.c:2367
 user_path_at_empty+0x3b/0x50 fs/namei.c:2647
 do_readlinkat+0x87/0x200 fs/stat.c:407
 __do_sys_readlink fs/stat.c:440 [inline]
 __se_sys_readlink fs/stat.c:437 [inline]
 __x64_sys_readlink+0x43/0x50 fs/stat.c:437
 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: 4894 Comm: systemd-udevd Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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