syzbot

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BUG: KCSAN: data-race in __d_drop.part.0 / dput

write to 0xffff8881250fb490 of 8 bytes by task 21170 on cpu 0:
 __d_drop.part.0+0x2b/0x70 fs/dcache.c:498
 __d_drop fs/dcache.c:496 [inline]
 __dentry_kill+0x11a/0x3c0 fs/dcache.c:574
 shrink_dentry_list+0x10e/0x1c0 fs/dcache.c:1122
 shrink_dcache_sb+0x107/0x1d0 fs/dcache.c:1242
 reconfigure_super+0x525/0x570 fs/super.c:938
 do_umount_root fs/namespace.c:1498 [inline]
 do_umount fs/namespace.c:1571 [inline]
 ksys_umount+0xa37/0xab0 fs/namespace.c:1698
 __do_sys_umount fs/namespace.c:1709 [inline]
 __se_sys_umount fs/namespace.c:1707 [inline]
 __x64_sys_umount+0x3a/0x50 fs/namespace.c:1707
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881250fb490 of 8 bytes by task 14707 on cpu 1:
 d_unhashed include/linux/dcache.h:336 [inline]
 fast_dput fs/dcache.c:783 [inline]
 dput+0x118/0x750 fs/dcache.c:846
 do_unlinkat+0x33a/0x530 fs/namei.c:4069
 __do_sys_unlink fs/namei.c:4114 [inline]
 __se_sys_unlink fs/namei.c:4112 [inline]
 __x64_sys_unlink+0x3b/0x50 fs/namei.c:4112
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14707 Comm: syz-executor.2 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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