syzbot

==================================================================
BUG: KCSAN: data-race in atime_needs_update / inode_update_timestamps

write to 0xffff88811efd7248 of 8 bytes by task 29843 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1657 [inline]
 inode_update_timestamps+0x136/0x270 fs/inode.c:2113
 generic_update_time fs/inode.c:2148 [inline]
 inode_update_time fs/inode.c:2168 [inline]
 file_update_time_flags+0x26c/0x310 fs/inode.c:2395
 file_update_time+0x17/0x20 fs/inode.c:2416
 shmem_file_write_iter+0x9c/0xf0 mm/shmem.c:3487
 iter_file_splice_write+0x66b/0xa20 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+0x312/0x680 fs/splice.c:1105
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 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+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811efd7248 of 8 bytes by task 29857 on cpu 0:
 inode_get_mtime_sec include/linux/fs.h:1639 [inline]
 inode_get_mtime include/linux/fs.h:1649 [inline]
 relatime_need_update fs/inode.c:2062 [inline]
 atime_needs_update+0x27b/0x3e0 fs/inode.c:2208
 touch_atime+0x4a/0x340 fs/inode.c:2223
 file_accessed include/linux/fs.h:2254 [inline]
 shmem_file_read_iter+0x477/0x540 mm/shmem.c:3470
 copy_splice_read+0x442/0x660 fs/splice.c:363
 do_splice_read fs/splice.c:981 [inline]
 splice_direct_to_actor+0x290/0x680 fs/splice.c:1086
 do_splice_direct_actor fs/splice.c:1204 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1230
 do_sendfile+0x380/0x650 fs/read_write.c:1370
 __do_sys_sendfile64 fs/read_write.c:1431 [inline]
 __se_sys_sendfile64 fs/read_write.c:1417 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
 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+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000069414a9f -> 0x0000000069414aa0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 29857 Comm: syz.1.7913 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================