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BUG: KCSAN: data-race in filemap_read / generic_write_end

write to 0xffff888109dffac8 of 8 bytes by task 13017 on cpu 0:
 i_size_write include/linux/fs.h:905 [inline]
 generic_write_end+0xb4/0x360 fs/buffer.c:2241
 ext4_da_write_end+0x4df/0x690 fs/ext4/inode.c:3012
 generic_perform_write+0x253/0x3d0 mm/filemap.c:3934
 ext4_buffered_write_iter+0x234/0x3e0 fs/ext4/file.c:289
 ext4_file_write_iter+0xd7/0x10e0
 call_write_iter include/linux/fs.h:1868 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x47b/0x780 fs/read_write.c:584
 ksys_write+0xeb/0x1a0 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:646
 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 0xffff888109dffac8 of 8 bytes by task 13018 on cpu 1:
 i_size_read include/linux/fs.h:883 [inline]
 filemap_read+0x1ca/0x680 mm/filemap.c:2687
 generic_file_read_iter+0x76/0x320 mm/filemap.c:2837
 ext4_file_read_iter+0x1cc/0x290
 call_read_iter include/linux/fs.h:1862 [inline]
 generic_file_splice_read+0xe3/0x290 fs/splice.c:419
 do_splice_to fs/splice.c:902 [inline]
 splice_direct_to_actor+0x25a/0x5f0 fs/splice.c:973
 do_splice_direct+0x104/0x180 fs/splice.c:1082
 do_sendfile+0x3b8/0x950 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64 fs/read_write.c:1308 [inline]
 __x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
 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: 0x0000000000d4d000 -> 0x0000000000d4e000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13018 Comm: syz-executor.1 Not tainted 6.4.0-rc3-syzkaller-00291-g4e893b5aa4ac #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
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