On Wed, May 28, 2025 at 03:22:26PM -0700, Darrick J. Wong wrote: > Welll... the only reason I patched the loop driver to turn ovn directio > by default is because writeback throttling for loop devices keeps > getting turned on and off randomly. At this point I have NFI if > throttling is actually the desired behavior or not. It makes fstests > crawl really slowly. > > On one hand it seems bogus that a loopbacked filesystem with enough > dirty pages to trip the thresholds then gets throttled doing writeback > to the pagecache of the loop file, but OTOH it /is/ more dirty > pagecache. Ultimately I think non-directio loop devices are stupid > especially when there are filesystems on top of them, but I bet there's > some user that would break if we suddenly started requiring directio > alignments. > > Maybe RWF_DONTCACHE will solve this whenever it stabilizes. Well, I'm all for using direct I/O loop devices by default. But having non-standard kernel hacks for that is pretty silly. Can we just make xfstests use direct I/O by default so that everyone uses the same configuration?
