syzbot

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BUG: KCSAN: data-race in atime_needs_update / inode_update_timestamps

write to 0xffff88811a2b0f7c of 4 bytes by task 16936 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1706 [inline]
 inode_update_timestamps+0x147/0x270 fs/inode.c:2022
 generic_update_time fs/inode.c:2057 [inline]
 inode_update_time fs/inode.c:2077 [inline]
 __file_update_time fs/inode.c:2305 [inline]
 file_update_time+0x20e/0x2b0 fs/inode.c:2335
 shmem_file_write_iter+0x9c/0xf0 mm/shmem.c:3461
 iter_file_splice_write+0x5ef/0x970 fs/splice.c:738
 do_splice_from fs/splice.c:935 [inline]
 direct_splice_actor+0x153/0x2a0 fs/splice.c:1158
 splice_direct_to_actor+0x30f/0x680 fs/splice.c:1102
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1227
 do_sendfile+0x380/0x640 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1415
 x64_sys_call+0xb39/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a2b0f7c of 4 bytes by task 16931 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1692 [inline]
 inode_get_mtime include/linux/fs.h:1698 [inline]
 relatime_need_update fs/inode.c:1971 [inline]
 atime_needs_update+0x2a8/0x3e0 fs/inode.c:2117
 touch_atime+0x4a/0x330 fs/inode.c:2132
 file_accessed include/linux/fs.h:2599 [inline]
 shmem_file_splice_read+0x582/0x5d0 mm/shmem.c:3623
 do_splice_read fs/splice.c:979 [inline]
 splice_direct_to_actor+0x26c/0x680 fs/splice.c:1083
 do_splice_direct_actor fs/splice.c:1201 [inline]
 do_splice_direct+0xda/0x150 fs/splice.c:1227
 do_sendfile+0x380/0x640 fs/read_write.c:1368
 __do_sys_sendfile64 fs/read_write.c:1429 [inline]
 __se_sys_sendfile64 fs/read_write.c:1415 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1415
 x64_sys_call+0xb39/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x018a420c -> 0x022a7683

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 16931 Comm: syz.3.4037 Not tainted 6.15.0-rc5-syzkaller-00204-g0e1329d4045c #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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