[$] Improving FUSE writeback performance

In a combined filesystem and memory-management session at the 2025 Linux Storage, Filesystem, MemoryManagement, and BPF Summit (LSFMM+BPF), Joanne Koong led a discussion onimproving the writeback performance for the Filesystem inUserspace (FUSE) layer. Writeback is how data that is written to thefilesystem is actually flushed to the disk; it is the process of writingdirty pages from the page cache to storage. The current FUSEimplementation allocates unmovable memory, then copies the dirty data to itbefore initiating writeback, which is slow; Koong wanted to change thatbehavior. Since the session, she has posted apatch set that has been appliedby FUSE maintainer Miklos Szeredi.