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BUG: KCSAN: data-race in filemap_map_pages / simple_write_end

write to 0xffff88811ece3550 of 8 bytes by task 8526 on cpu 1:
 i_size_write include/linux/fs.h:876 [inline]
 simple_write_end+0x1fa/0x360 fs/libfs.c:587
 generic_perform_write+0x23b/0x390 mm/filemap.c:3414
 __generic_file_write_iter+0x154/0x330 mm/filemap.c:3532
 generic_file_write_iter+0x2f3/0x3e0 mm/filemap.c:3564
 call_write_iter include/linux/fs.h:1882 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x665/0x6f0 fs/read_write.c:578
 ksys_write+0xce/0x180 fs/read_write.c:631
 __do_sys_write fs/read_write.c:643 [inline]
 __se_sys_write fs/read_write.c:640 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:640
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811ece3550 of 8 bytes by task 8529 on cpu 0:
 i_size_read include/linux/fs.h:854 [inline]
 filemap_map_pages+0x649/0x9a0 mm/filemap.c:2728
 do_fault_around mm/memory.c:3817 [inline]
 do_read_fault+0x22f/0x760 mm/memory.c:3851
 do_fault mm/memory.c:3984 [inline]
 handle_pte_fault mm/memory.c:4224 [inline]
 __handle_mm_fault mm/memory.c:4359 [inline]
 handle_mm_fault+0x14e9/0x1af0 mm/memory.c:4457
 faultin_page mm/gup.c:887 [inline]
 __get_user_pages+0xac0/0x1080 mm/gup.c:1105
 populate_vma_page_range mm/gup.c:1435 [inline]
 __mm_populate+0x24d/0x340 mm/gup.c:1483
 mm_populate include/linux/mm.h:2564 [inline]
 vm_mmap_pgoff+0x133/0x170 mm/util.c:511
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1596
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8529 Comm: syz-executor.5 Not tainted 5.9.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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