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BUG: KCSAN: data-race in filemap_read / generic_write_end

write to 0xffff88810a57f648 of 8 bytes by task 6918 on cpu 0:
 i_size_write include/linux/fs.h:888 [inline]
 generic_write_end+0xb4/0x360 fs/buffer.c:2211
 ext4_da_write_end+0x4bd/0x630 fs/ext4/inode.c:3174
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3937
 ext4_buffered_write_iter+0x234/0x3e0 fs/ext4/file.c:289
 ext4_file_write_iter+0xd7/0x10e0
 do_iter_write+0x418/0x700 fs/read_write.c:861
 vfs_iter_write+0x50/0x70 fs/read_write.c:902
 iter_file_splice_write+0x456/0x7d0 fs/splice.c:778
 do_splice_from fs/splice.c:856 [inline]
 direct_splice_actor+0x84/0xa0 fs/splice.c:1023
 splice_direct_to_actor+0x2ee/0x5f0 fs/splice.c:978
 do_splice_direct+0x104/0x180 fs/splice.c:1066
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1317 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff88810a57f648 of 8 bytes by task 6926 on cpu 1:
 i_size_read include/linux/fs.h:866 [inline]
 filemap_read+0x247/0x680 mm/filemap.c:2706
 generic_file_read_iter+0x76/0x320 mm/filemap.c:2840
 ext4_file_read_iter+0x1cc/0x290
 call_read_iter include/linux/fs.h:1845 [inline]
 generic_file_splice_read+0xe3/0x290 fs/splice.c:402
 do_splice_to fs/splice.c:885 [inline]
 splice_direct_to_actor+0x25a/0x5f0 fs/splice.c:957
 do_splice_direct+0x104/0x180 fs/splice.c:1066
 do_sendfile+0x3b8/0x950 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1317 [inline]
 __se_sys_sendfile64 fs/read_write.c:1309 [inline]
 __x64_sys_sendfile64+0xbd/0x150 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000001cb0 -> 0x0000000000001d38

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6926 Comm: syz-executor.2 Not tainted 6.3.0-rc1-syzkaller-00019-g6a98c9cae232 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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