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BUG: KCSAN: data-race in __fsnotify_parent / d_set_mounted

write to 0xffff88810f1dd180 of 4 bytes by task 29502 on cpu 0:
 d_set_mounted+0xfc/0x190 fs/dcache.c:1466
 get_mountpoint+0x1be/0x300 fs/namespace.c:740
 lock_mount+0x86/0x1d0 fs/namespace.c:2206
 do_loopback fs/namespace.c:2355 [inline]
 path_mount+0xcb7/0x1ca0 fs/namespace.c:3205
 do_mount fs/namespace.c:3224 [inline]
 __do_sys_mount fs/namespace.c:3432 [inline]
 __se_sys_mount+0x23d/0x2e0 fs/namespace.c:3409
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3409
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810f1dd180 of 4 bytes by task 29500 on cpu 1:
 __fsnotify_parent+0x7d/0x430 fs/notify/fsnotify.c:187
 fsnotify_parent include/linux/fsnotify.h:68 [inline]
 fsnotify_file include/linux/fsnotify.h:90 [inline]
 fsnotify_perm+0x299/0x2e0 include/linux/fsnotify.h:115
 security_file_permission+0x87/0xa0 security/security.c:1452
 rw_verify_area+0x136/0x250 fs/read_write.c:400
 do_splice_to fs/splice.c:779 [inline]
 splice_direct_to_actor+0x23a/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5e0/0xcf0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 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: 1 PID: 29500 Comm: syz-executor.0 Not tainted 5.11.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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