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BUG: KCSAN: data-race in filemap_map_pages / shmem_write_end

write to 0xffff88810d6017e0 of 8 bytes by task 1888 on cpu 1:
 i_size_write include/linux/fs.h:870 [inline]
 shmem_write_end+0x62/0x650 mm/shmem.c:2539
 generic_perform_write+0x23e/0x3a0 mm/filemap.c:3423
 __generic_file_write_iter+0x15c/0x340 mm/filemap.c:3541
 generic_file_write_iter+0x75/0x130 mm/filemap.c:3573
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x41a/0x770 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5e0/0xcf0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88810d6017e0 of 8 bytes by task 1890 on cpu 0:
 i_size_read include/linux/fs.h:848 [inline]
 filemap_map_pages+0x481/0x9b0 mm/filemap.c:2960
 do_fault_around mm/memory.c:3980 [inline]
 do_read_fault+0x22f/0x720 mm/memory.c:4014
 do_fault mm/memory.c:4147 [inline]
 handle_pte_fault mm/memory.c:4387 [inline]
 __handle_mm_fault mm/memory.c:4522 [inline]
 handle_mm_fault+0x100c/0x1810 mm/memory.c:4620
 do_user_addr_fault+0x43e/0x830 arch/x86/mm/fault.c:1393
 handle_page_fault arch/x86/mm/fault.c:1450 [inline]
 exc_page_fault+0x94/0x2a0 arch/x86/mm/fault.c:1506
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:580
 copy_user_enhanced_fast_string+0xe/0x40 arch/x86/lib/copy_user_64.S:205
 copy_user_generic arch/x86/include/asm/uaccess_64.h:37 [inline]
 raw_copy_from_user arch/x86/include/asm/uaccess_64.h:52 [inline]
 _copy_from_user+0x7e/0xd0 lib/usercopy.c:16
 copy_from_user include/linux/uaccess.h:192 [inline]
 __get_filter+0xc7/0x210 net/core/filter.c:1495
 sk_attach_filter+0x21/0x270 net/core/filter.c:1526
 sock_setsockopt+0x1409/0x2080 net/core/sock.c:1068
 __sys_setsockopt+0x337/0x460 net/socket.c:2111
 __do_sys_setsockopt net/socket.c:2126 [inline]
 __se_sys_setsockopt net/socket.c:2123 [inline]
 __x64_sys_setsockopt+0x62/0x70 net/socket.c:2123
 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: 1890 Comm: syz-executor.1 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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