On Thu, Aug 22, 2019 at 8:38 PM Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > > There have previously been snapshots, typically prior to doing system > updates. Is this an example of extents being pinned due to snapshots, > and then extents updated and are now "stuck"? I'm kinda surprised, in > that I'd expect most programs, especially RPM, are writing out new > files entirely, then deleting obsolete files, then renaming. But... > this suggests something is doing partial overwrites of file extents > rather than replacements. It's databases. Databases are updating their files with block overwrites, btrfs COWs them. And if there's a snapshot that exists while COW happens, partial extents get pinned. This affects the firefox database files, and also RPM's. It's a small effect on my system, but it's a curious issue in particular if the files were much larger. -- Chris Murphy
