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BUG: KCSAN: data-race in file_update_time / generic_update_time

write to 0xffff888129da5a60 of 16 bytes by task 12875 on cpu 0:
 generic_update_time+0x109/0x270 fs/inode.c:1674
 update_time+0x85/0x90 fs/inode.c:1694
 file_update_time+0x205/0x2d0 fs/inode.c:1909
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2656
 do_page_mkwrite+0x100/0x210 mm/memory.c:2364
 do_shared_fault mm/memory.c:3738 [inline]
 do_fault mm/memory.c:3806 [inline]
 handle_pte_fault mm/memory.c:4033 [inline]
 __handle_mm_fault+0x1e45/0x2e00 mm/memory.c:4163
 handle_mm_fault+0x21b/0x530 mm/memory.c:4200
 faultin_page mm/gup.c:659 [inline]
 __get_user_pages+0x485/0x1130 mm/gup.c:870
 __get_user_pages_locked mm/gup.c:1057 [inline]
 get_user_pages_remote+0x227/0x440 mm/gup.c:1654
 pin_user_pages_remote+0x50/0x70 mm/gup.c:2551
 process_vm_rw_single_vec mm/process_vm_access.c:108 [inline]
 process_vm_rw_core.isra.0+0x38f/0x820 mm/process_vm_access.c:218
 process_vm_rw+0x1c4/0x1e0 mm/process_vm_access.c:286
 __do_sys_process_vm_writev mm/process_vm_access.c:308 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __x64_sys_process_vm_writev+0x8b/0xb0 mm/process_vm_access.c:303
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888129da5a68 of 8 bytes by task 12883 on cpu 1:
 timespec64_equal include/linux/time64.h:52 [inline]
 file_update_time+0xee/0x2d0 fs/inode.c:1893
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2656
 do_page_mkwrite+0x100/0x210 mm/memory.c:2364
 do_shared_fault mm/memory.c:3738 [inline]
 do_fault mm/memory.c:3806 [inline]
 handle_pte_fault mm/memory.c:4033 [inline]
 __handle_mm_fault+0x1e45/0x2e00 mm/memory.c:4163
 handle_mm_fault+0x21b/0x530 mm/memory.c:4200
 faultin_page mm/gup.c:659 [inline]
 __get_user_pages+0x485/0x1130 mm/gup.c:870
 __get_user_pages_locked mm/gup.c:1057 [inline]
 get_user_pages_remote+0x227/0x440 mm/gup.c:1654
 pin_user_pages_remote+0x50/0x70 mm/gup.c:2551
 process_vm_rw_single_vec mm/process_vm_access.c:108 [inline]
 process_vm_rw_core.isra.0+0x38f/0x820 mm/process_vm_access.c:218
 process_vm_rw+0x1c4/0x1e0 mm/process_vm_access.c:286
 __do_sys_process_vm_writev mm/process_vm_access.c:308 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __x64_sys_process_vm_writev+0x8b/0xb0 mm/process_vm_access.c:303
 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: 12883 Comm: syz-executor.2 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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