syzbot

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BUG: KCSAN: data-race in link_path_walk / shrink_dentry_list

write to 0xffff888101375a80 of 4 bytes by task 22993 on cpu 1:
 d_shrink_add fs/dcache.c:431 [inline]
 __dput_to_list fs/dcache.c:903 [inline]
 shrink_dentry_list+0x489/0x580 fs/dcache.c:1175
 shrink_dcache_sb+0x188/0x2d0 fs/dcache.c:1296
 reconfigure_super+0x2aa/0x4f0 fs/super.c:889
 do_remount fs/namespace.c:2639 [inline]
 path_mount+0x1442/0x1ce0 fs/namespace.c:3227
 do_mount fs/namespace.c:3248 [inline]
 __do_sys_mount fs/namespace.c:3456 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3433
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3433
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888101375a80 of 4 bytes by task 1 on cpu 0:
 __d_entry_type include/linux/dcache.h:395 [inline]
 d_can_lookup include/linux/dcache.h:410 [inline]
 link_path_walk+0x4d7/0x780 fs/namei.c:2279
 path_openat+0x1a0/0x20b0 fs/namei.c:3490
 do_filp_open+0xd9/0x1f0 fs/namei.c:3521
 do_sys_openat2+0xa3/0x250 fs/open.c:1187
 do_sys_open fs/open.c:1203 [inline]
 __do_sys_open fs/open.c:1211 [inline]
 __se_sys_open fs/open.c:1207 [inline]
 __x64_sys_open+0xe2/0x110 fs/open.c:1207
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1 Comm: systemd Tainted: G        W         5.13.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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