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BUG: KCSAN: data-race in atime_needs_update / touch_atime

write to 0xffff888106472608 of 8 bytes by task 20726 on cpu 0:
 inode_set_atime_to_ts include/linux/fs.h:1541 [inline]
 inode_update_timestamps fs/inode.c:1876 [inline]
 generic_update_time fs/inode.c:1898 [inline]
 inode_update_time fs/inode.c:1918 [inline]
 touch_atime+0x1ed/0x340 fs/inode.c:1990
 file_accessed include/linux/fs.h:2434 [inline]
 filemap_splice_read+0x837/0x8f0 mm/filemap.c:2928
 ext4_file_splice_read+0x95/0xb0 fs/ext4/file.c:158
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x268/0x660 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888106472608 of 8 bytes by task 20709 on cpu 1:
 atime_needs_update+0x264/0x3f0
 touch_atime+0x4a/0x340 fs/inode.c:1973
 file_accessed include/linux/fs.h:2434 [inline]
 filemap_splice_read+0x837/0x8f0 mm/filemap.c:2928
 ext4_file_splice_read+0x95/0xb0 fs/ext4/file.c:158
 do_splice_read fs/splice.c:985 [inline]
 splice_direct_to_actor+0x268/0x660 fs/splice.c:1089
 do_splice_direct_actor fs/splice.c:1207 [inline]
 do_splice_direct+0xd7/0x150 fs/splice.c:1233
 do_sendfile+0x3b9/0x960 fs/read_write.c:1295
 __do_sys_sendfile64 fs/read_write.c:1356 [inline]
 __se_sys_sendfile64 fs/read_write.c:1348 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1348
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x000000001fe43502 -> 0x0000000020845530

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20709 Comm: syz-executor.2 Tainted: G        W          6.8.0-rc4-syzkaller-00388-gced590523156 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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