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BUG: KCSAN: data-race in file_update_time / generic_update_time

write to 0xffff88812a37ed08 of 16 bytes by task 10289 on cpu 0:
 generic_update_time+0xc2/0x270 fs/inode.c:1658
 update_time fs/inode.c:1683 [inline]
 file_update_time+0x237/0x300 fs/inode.c:1898
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2698
 do_page_mkwrite+0x100/0x210 mm/memory.c:2208
 do_shared_fault mm/memory.c:3554 [inline]
 do_fault mm/memory.c:3622 [inline]
 handle_pte_fault mm/memory.c:3849 [inline]
 __handle_mm_fault+0x2099/0x2cb0 mm/memory.c:3973
 handle_mm_fault+0x21b/0x530 mm/memory.c:4010
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x3fb/0x9e0 arch/x86/mm/fault.c:1506
 do_page_fault+0x54/0x233 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1202
 copy_user_enhanced_fast_string+0xe/0x30 arch/x86/lib/copy_user_64.S:204
 copy_page_to_iter_iovec lib/iov_iter.c:211 [inline]
 copy_page_to_iter+0x254/0x8b0 lib/iov_iter.c:900
 generic_file_buffered_read mm/filemap.c:2143 [inline]
 generic_file_read_iter+0x978/0x1440 mm/filemap.c:2323
 blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2010
 call_read_iter include/linux/fs.h:1889 [inline]
 do_iter_readv_writev+0x54b/0x5b0 fs/read_write.c:691

read to 0xffff88812a37ed08 of 8 bytes by task 10295 on cpu 1:
 file_update_time+0x12a/0x300 fs/inode.c:1885
 filemap_page_mkwrite+0xae/0x1d0 mm/filemap.c:2698
 do_page_mkwrite+0x100/0x210 mm/memory.c:2208
 do_shared_fault mm/memory.c:3554 [inline]
 do_fault mm/memory.c:3622 [inline]
 handle_pte_fault mm/memory.c:3849 [inline]
 __handle_mm_fault+0x2099/0x2cb0 mm/memory.c:3973
 handle_mm_fault+0x21b/0x530 mm/memory.c:4010
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x3fb/0x9e0 arch/x86/mm/fault.c:1506
 do_page_fault+0x54/0x233 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1202
 copy_user_enhanced_fast_string+0xe/0x30 arch/x86/lib/copy_user_64.S:204
 copy_page_to_iter_iovec lib/iov_iter.c:211 [inline]
 copy_page_to_iter+0x254/0x8b0 lib/iov_iter.c:900
 generic_file_buffered_read mm/filemap.c:2143 [inline]
 generic_file_read_iter+0x978/0x1440 mm/filemap.c:2323
 blkdev_read_iter+0xb2/0xe0 fs/block_dev.c:2010
 call_read_iter include/linux/fs.h:1889 [inline]
 do_iter_readv_writev+0x54b/0x5b0 fs/read_write.c:691

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10295 Comm: syz-executor.4 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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