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BUG: KCSAN: data-race in ext4_dio_write_end_io / filemap_fault

write to 0xffff8881065b5b70 of 8 bytes by task 29529 on cpu 1:
 i_size_write include/linux/fs.h:871 [inline]
 ext4_dio_write_end_io+0xd3/0x100 fs/ext4/file.c:399
 iomap_dio_complete+0xb8/0x3c0 fs/iomap/direct-io.c:88
 iomap_dio_rw+0x4e/0x70 fs/iomap/direct-io.c:652
 ext4_dio_write_iter fs/ext4/file.c:568 [inline]
 ext4_file_write_iter+0xa04/0x11d0 fs/ext4/file.c:678
 call_write_iter include/linux/fs.h:2114 [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+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x773/0xda0 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881065b5b70 of 8 bytes by task 29523 on cpu 0:
 i_size_read include/linux/fs.h:849 [inline]
 filemap_fault+0x88/0x7b0 mm/filemap.c:2971
 ext4_filemap_fault+0x4b/0x60 fs/ext4/inode.c:6194
 __do_fault mm/memory.c:3721 [inline]
 do_shared_fault mm/memory.c:4079 [inline]
 do_fault mm/memory.c:4157 [inline]
 handle_pte_fault mm/memory.c:4412 [inline]
 __handle_mm_fault mm/memory.c:4547 [inline]
 handle_mm_fault+0xf76/0x1a70 mm/memory.c:4645
 do_user_addr_fault+0x609/0xc00 arch/x86/mm/fault.c:1390
 handle_page_fault arch/x86/mm/fault.c:1475 [inline]
 exc_page_fault+0x91/0x230 arch/x86/mm/fault.c:1531
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577

value changed: 0x0000000000001a00 -> 0x0000000000002c00

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29523 Comm: syz-executor.0 Not tainted 5.13.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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