syzbot

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BUG: KCSAN: data-race in atime_needs_update / inode_update_time

write to 0xffff888119a12c8c of 4 bytes by task 17708 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1659 [inline]
 inode_update_cmtime fs/inode.c:2130 [inline]
 inode_update_time+0x2cc/0x360 fs/inode.c:2155
 generic_update_time fs/inode.c:2186 [inline]
 file_update_time_flags+0x277/0x2e0 fs/inode.c:2419
 file_update_time+0x17/0x20 fs/inode.c:2440
 shmem_file_write_iter+0x9c/0xf0 mm/shmem.c:3516
 iter_file_splice_write+0x6bc/0xa80 fs/splice.c:738
 do_splice_from fs/splice.c:938 [inline]
 direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
 splice_direct_to_actor+0x311/0x670 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1230
 do_sendfile+0x382/0x650 fs/read_write.c:1372
 __do_sys_sendfile64 fs/read_write.c:1433 [inline]
 __se_sys_sendfile64 fs/read_write.c:1419 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
 x64_sys_call+0x2db1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888119a12c8c of 4 bytes by task 17712 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1645 [inline]
 inode_get_mtime include/linux/fs.h:1651 [inline]
 relatime_need_update fs/inode.c:2065 [inline]
 atime_needs_update+0x2a8/0x3e0 fs/inode.c:2229
 touch_atime+0x4a/0x330 fs/inode.c:2244
 file_accessed include/linux/fs.h:2263 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3499
 copy_splice_read+0x471/0x6c0 fs/splice.c:363
 do_splice_read fs/splice.c:981 [inline]
 splice_direct_to_actor+0x28f/0x670 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1230
 do_sendfile+0x382/0x650 fs/read_write.c:1372
 __do_sys_sendfile64 fs/read_write.c:1433 [inline]
 __se_sys_sendfile64 fs/read_write.c:1419 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
 x64_sys_call+0x2db1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0e4e28d8 -> 0x0f07fcd5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 17712 Comm: syz.1.4327 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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