syzbot

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BUG: KCSAN: data-race in d_make_discardable / step_into_slowpath

write to 0xffff888119cee0c0 of 4 bytes by task 3309 on cpu 0:
 d_make_discardable+0x4f/0xa0 fs/dcache.c:936
 simple_unlink+0x68/0x80 fs/libfs.c:815
 shmem_unlink+0x12d/0x140 mm/shmem.c:3991
 vfs_unlink+0x28b/0x440 fs/namei.c:5369
 do_unlinkat+0x1cd/0x4b0 fs/namei.c:5439
 __do_sys_unlink fs/namei.c:5474 [inline]
 __se_sys_unlink fs/namei.c:5472 [inline]
 __x64_sys_unlink+0x2e/0x40 fs/namei.c:5472
 x64_sys_call+0x2f48/0x3000 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888119cee0c0 of 4 bytes by task 3005 on cpu 1:
 __d_entry_type include/linux/dcache.h:416 [inline]
 d_is_symlink include/linux/dcache.h:446 [inline]
 step_into_slowpath+0x120/0x480 fs/namei.c:2047
 step_into fs/namei.c:2091 [inline]
 walk_component fs/namei.c:2227 [inline]
 lookup_last fs/namei.c:2722 [inline]
 path_lookupat+0x330/0x500 fs/namei.c:2746
 filename_lookup+0x147/0x340 fs/namei.c:2775
 do_readlinkat+0x7d/0x320 fs/stat.c:576
 __do_sys_readlink fs/stat.c:613 [inline]
 __se_sys_readlink fs/stat.c:610 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:610
 x64_sys_call+0x2af1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08300080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3005 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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