On Sun, Apr 9, 2023 at 2:18 PM Andres Freund <and...@anarazel.de> wrote: > On 2023-04-09 13:55:33 +1200, Thomas Munro wrote: > > I think that particular thing might relate to modifications of the > > user buffer while a write is in progress (breaking btrfs's internal > > checksums). I don't think we should ever do that ourselves (not least > > because it'd break our own checksums). We lock the page during the > > write so no one can do that, and then we sleep in a synchronous > > syscall. > > Oh, but we actually *do* modify pages while IO is going on. I wonder if you > hit the jack pot here. The content lock doesn't prevent hint bit > writes. That's why we copy the page to temporary memory when computing > checksums.
More like the jackpot hit me. Woo, I can now reproduce this locally on a loop filesystem. Previously I had missed a step, the parallel worker seems to be necessary. More soon.
