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BUG: KCSAN: data-race in file_update_time / generic_update_time

read to 0xffff88812a7b86a8 of 8 bytes by task 12200 on cpu 0:
 file_update_time+0xbb/0x300 fs/inode.c:1882
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2678
 do_page_mkwrite+0x100/0x210 mm/memory.c:2276
 do_shared_fault mm/memory.c:3650 [inline]
 do_fault mm/memory.c:3718 [inline]
 handle_pte_fault mm/memory.c:3945 [inline]
 __handle_mm_fault+0x1e45/0x2e00 mm/memory.c:4075
 handle_mm_fault+0x21b/0x530 mm/memory.c:4112
 faultin_page mm/gup.c:640 [inline]
 __get_user_pages+0x485/0x1130 mm/gup.c:851
 __get_user_pages_locked mm/gup.c:1029 [inline]
 get_user_pages_remote+0x206/0x3e0 mm/gup.c:1175
 process_vm_rw_single_vec mm/process_vm_access.c:109 [inline]
 process_vm_rw_core.isra.0+0x3a4/0x910 mm/process_vm_access.c:216
 process_vm_rw+0x1c4/0x1e0 mm/process_vm_access.c:284
 __do_sys_process_vm_writev mm/process_vm_access.c:306 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:301 [inline]
 __x64_sys_process_vm_writev+0x8b/0xb0 mm/process_vm_access.c:301
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff88812a7b86a8 of 16 bytes by task 12194 on cpu 1:
 generic_update_time+0x109/0x270 fs/inode.c:1660
 update_time fs/inode.c:1683 [inline]
 file_update_time+0x237/0x300 fs/inode.c:1898
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2678
 do_page_mkwrite+0x100/0x210 mm/memory.c:2276
 do_shared_fault mm/memory.c:3650 [inline]
 do_fault mm/memory.c:3718 [inline]
 handle_pte_fault mm/memory.c:3945 [inline]
 __handle_mm_fault+0x1e45/0x2e00 mm/memory.c:4075
 handle_mm_fault+0x21b/0x530 mm/memory.c:4112
 faultin_page mm/gup.c:640 [inline]
 __get_user_pages+0x485/0x1130 mm/gup.c:851
 __get_user_pages_locked mm/gup.c:1072 [inline]
 get_user_pages_remote+0x17d/0x3e0 mm/gup.c:1175
 process_vm_rw_single_vec mm/process_vm_access.c:109 [inline]
 process_vm_rw_core.isra.0+0x3a4/0x910 mm/process_vm_access.c:216
 process_vm_rw+0x1c4/0x1e0 mm/process_vm_access.c:284
 __do_sys_process_vm_writev mm/process_vm_access.c:306 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:301 [inline]
 __x64_sys_process_vm_writev+0x8b/0xb0 mm/process_vm_access.c:301
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12194 Comm: syz-executor.4 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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