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BUG: KCSAN: data-race in next_uptodate_page / shmem_write_end

write to 0xffff88812de420d8 of 8 bytes by task 5586 on cpu 0:
 shmem_write_end+0x5d/0x3b0
 generic_perform_write+0x253/0x3d0
 __generic_file_write_iter+0xe6/0x290
 generic_file_write_iter+0x7d/0x1c0
 vfs_write+0x45a/0x750
 ksys_write+0xeb/0x1a0
 __x64_sys_write+0x42/0x50
 do_syscall_64+0x41/0xc0
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88812de420d8 of 8 bytes by task 5597 on cpu 1:
 next_uptodate_page+0x47b/0x560
 filemap_map_pages+0x722/0x830
 handle_mm_fault+0x1044/0x24d0
 __get_user_pages+0x353/0xc60
 __mm_populate+0x23a/0x360
 vm_mmap_pgoff+0x174/0x210
 ksys_mmap_pgoff+0x2ac/0x320
 do_syscall_64+0x41/0xc0
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x000000000081b000 -> 0x000000000081e000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5597 Comm: syz-executor.1 Tainted: G        W          6.2.0-rc6-syzkaller-00258-gdb27c22251e7-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
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