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BUG: KCSAN: data-race in atime_needs_update / inode_update_time

write to 0xffff88811c76749c of 4 bytes by task 12576 on cpu 0:
 inode_set_mtime_to_ts include/linux/fs.h:1655 [inline]
 inode_update_cmtime fs/inode.c:2198 [inline]
 inode_update_time+0x2ce/0x360 fs/inode.c:2223
 generic_update_time fs/inode.c:2254 [inline]
 file_update_time_flags+0x277/0x2e0 fs/inode.c:2487
 file_update_time+0x17/0x20 fs/inode.c:2508
 shmem_file_write_iter+0x9c/0xf0 mm/shmem.c:3421
 iter_file_splice_write+0x6a0/0xa60 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x156/0x280 fs/splice.c:1159
 splice_direct_to_actor+0x2f9/0x680 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811c76749c of 4 bytes by task 12571 on cpu 1:
 inode_get_mtime_nsec include/linux/fs.h:1641 [inline]
 inode_get_mtime include/linux/fs.h:1647 [inline]
 relatime_need_update fs/inode.c:2127 [inline]
 atime_needs_update+0x2a8/0x3e0 fs/inode.c:2297
 touch_atime+0x4a/0x300 fs/inode.c:2312
 file_accessed include/linux/fs.h:2272 [inline]
 shmem_file_read_iter+0x3ed/0x4b0 mm/shmem.c:3404
 copy_splice_read+0x47a/0x6b0 fs/splice.c:362
 do_splice_read fs/splice.c:979 [inline]
 splice_direct_to_actor+0x27c/0x680 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x119/0x1a0 fs/splice.c:1228
 do_sendfile+0x37d/0x640 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64 fs/read_write.c:1418 [inline]
 __x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1418
 x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0333c891 -> 0x03cc5f11

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 12571 Comm: syz.6.2824 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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