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BUG: KCSAN: data-race in filemap_fault / ondemand_readahead

write to 0xffff88810b5b8098 of 8 bytes by task 16304 on cpu 1:
 do_sync_mmap_readahead mm/filemap.c:2649 [inline]
 filemap_fault+0x66a/0x12e0 mm/filemap.c:2741
 __do_fault mm/memory.c:3612 [inline]
 do_shared_fault+0xc3/0x7a0 mm/memory.c:4060
 do_fault mm/memory.c:4138 [inline]
 handle_pte_fault mm/memory.c:4374 [inline]
 __handle_mm_fault mm/memory.c:4509 [inline]
 handle_mm_fault+0x127c/0x1770 mm/memory.c:4607
 do_user_addr_fault+0x33e/0x730 arch/x86/mm/fault.c:1372
 handle_page_fault arch/x86/mm/fault.c:1429 [inline]
 exc_page_fault+0x91/0x290 arch/x86/mm/fault.c:1485
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583
 __put_user_nocheck_4+0x3/0x11
 __sys_socketpair+0xb2/0x800 net/socket.c:1565
 __do_sys_socketpair net/socket.c:1631 [inline]
 __se_sys_socketpair net/socket.c:1628 [inline]
 __x64_sys_socketpair+0x4e/0x60 net/socket.c:1628
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810b5b8098 of 8 bytes by task 16287 on cpu 0:
 ondemand_readahead+0x15e/0x780 mm/readahead.c:462
 page_cache_async_ra+0x1aa/0x1d0 mm/readahead.c:607
 page_cache_async_readahead include/linux/pagemap.h:862 [inline]
 do_async_mmap_readahead mm/filemap.c:2680 [inline]
 filemap_fault+0x310/0x12e0 mm/filemap.c:2735
 __do_fault mm/memory.c:3612 [inline]
 do_read_fault+0x403/0x760 mm/memory.c:4006
 do_fault mm/memory.c:4134 [inline]
 handle_pte_fault mm/memory.c:4374 [inline]
 __handle_mm_fault mm/memory.c:4509 [inline]
 handle_mm_fault+0xfeb/0x1770 mm/memory.c:4607
 faultin_page mm/gup.c:885 [inline]
 __get_user_pages+0x8ec/0xe50 mm/gup.c:1097
 populate_vma_page_range mm/gup.c:1430 [inline]
 __mm_populate+0x24d/0x340 mm/gup.c:1478
 mm_populate include/linux/mm.h:2590 [inline]
 vm_mmap_pgoff+0x133/0x170 mm/util.c:512
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1634
 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: 16287 Comm: syz-executor.4 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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