syzbot

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BUG: KCSAN: data-race in __d_drop / fast_dput

write to 0xffff888106212310 of 8 bytes by task 7461 on cpu 0:
 __d_drop+0x13d/0x1e0 fs/dcache.c:483
 __dentry_kill+0x12f/0x4e0 fs/dcache.c:577
 shrink_dentry_list+0x1bb/0x340 fs/dcache.c:1176
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1296
 reconfigure_super+0x2aa/0x4f0 fs/super.c:889
 do_remount fs/namespace.c:2650 [inline]
 path_mount+0x145a/0x1d20 fs/namespace.c:3310
 do_mount fs/namespace.c:3331 [inline]
 __do_sys_mount fs/namespace.c:3539 [inline]
 __se_sys_mount+0x24b/0x2f0 fs/namespace.c:3516
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3516
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888106212310 of 8 bytes by task 1119 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:342 [inline]
 fast_dput+0x92/0x1c0 fs/dcache.c:812
 dput+0x26/0x360 fs/dcache.c:875
 path_umount+0xde/0xa70 fs/namespace.c:1756
 ksys_umount fs/namespace.c:1776 [inline]
 __do_sys_umount fs/namespace.c:1781 [inline]
 __se_sys_umount fs/namespace.c:1779 [inline]
 __x64_sys_umount+0xb5/0xe0 fs/namespace.c:1779
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff88823776a2f8 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1119 Comm: syz-executor.5 Not tainted 5.15.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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