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BUG: KCSAN: data-race in dentry_lru_isolate_shrink / step_into

write to 0xffff88812897c180 of 4 bytes by task 10953 on cpu 0:
 d_lru_shrink_move fs/dcache.c:453 [inline]
 dentry_lru_isolate_shrink+0x7f/0x120 fs/dcache.c:1273
 __list_lru_walk_one+0xfb/0x320 mm/list_lru.c:222
 list_lru_walk_one mm/list_lru.c:266 [inline]
 list_lru_walk_node+0x69/0x1e0 mm/list_lru.c:295
 list_lru_walk include/linux/list_lru.h:215 [inline]
 shrink_dcache_sb+0x97/0x1c0 fs/dcache.c:1292
 reconfigure_super+0x2aa/0x4f0 fs/super.c:888
 do_remount fs/namespace.c:2637 [inline]
 path_mount+0x1444/0x1ce0 fs/namespace.c:3225
 do_mount fs/namespace.c:3246 [inline]
 __do_sys_mount fs/namespace.c:3454 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3431
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3431
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812897c180 of 4 bytes by task 1766 on cpu 1:
 __d_entry_type include/linux/dcache.h:394 [inline]
 d_is_symlink include/linux/dcache.h:424 [inline]
 step_into+0x158/0xec0 fs/namei.c:1777
 handle_lookup_down fs/namei.c:2405 [inline]
 path_lookupat+0x4bf/0x570 fs/namei.c:2425
 filename_lookup+0xff/0x390 fs/namei.c:2455
 user_path_at_empty+0x3b/0x50 fs/namei.c:2735
 user_path_at include/linux/namei.h:60 [inline]
 ksys_umount fs/namespace.c:1775 [inline]
 __do_sys_umount fs/namespace.c:1783 [inline]
 __se_sys_umount fs/namespace.c:1781 [inline]
 __x64_sys_umount+0x75/0xd0 fs/namespace.c:1781
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1766 Comm: syz-executor.1 Not tainted 5.12.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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