[$] Initiating writeback earlier

Writeback is the process of ensuring that dirty pages or folios in the pagecache are flushed to the disk, so that changes to those files are madepersistent. In a filesystem-track session at the 2026 Linux Storage,Filesystem, Memory Management, and BPF Summit, Jeff Layton wanted todiscuss whether the writeback operation should be initiated earlier than itis today. The consensus seemed to be that it should be done earlier, butthe path toward making that happen was less clear.