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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

write to 0xffff8881253d20c0 of 4 bytes by task 22231 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:390 [inline]
 __d_instantiate+0x2b0/0x310 fs/dcache.c:1931
 d_instantiate+0x65/0x90 fs/dcache.c:1956
 shmem_symlink+0x1b6/0x3e0 mm/shmem.c:3149
 vfs_symlink fs/namei.c:4201 [inline]
 vfs_symlink+0x216/0x310 fs/namei.c:4187
 do_symlinkat+0x1ac/0x1e0 fs/namei.c:4228
 __do_sys_symlink fs/namei.c:4247 [inline]
 __se_sys_symlink fs/namei.c:4245 [inline]
 __x64_sys_symlink+0x3c/0x50 fs/namei.c:4245
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881253d20c0 of 4 bytes by task 4029 on cpu 1:
 d_revalidate fs/namei.c:765 [inline]
 lookup_fast+0x1cd/0x6e0 fs/namei.c:1690
 walk_component+0x73/0x9a0 fs/namei.c:1911
 lookup_last fs/namei.c:2391 [inline]
 path_lookupat.isra.0+0x129/0x2e0 fs/namei.c:2436
 filename_lookup+0x145/0x2b0 fs/namei.c:2466
 user_path_at_empty+0x47/0x60 fs/namei.c:2746
 do_readlinkat+0x89/0x230 fs/stat.c:409
 __do_sys_readlink fs/stat.c:442 [inline]
 __se_sys_readlink fs/stat.c:439 [inline]
 __x64_sys_readlink+0x4c/0x60 fs/stat.c:439
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4029 Comm: udevd Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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