[$] Buffered atomic writes, writethrough, and more

In back-to-back sessions at the start of the 2026 Linux Storage,Filesystem, Memory Management, and BPF Summit (which spilled over intoa third slot), the atomic-buffered-writesfeature was discussed. In the first session, Pankaj Raghav and AndresFreund set the stage with an introduction to the problem, along with a usecase for its solution: the PostgreSQL database system. In the second, Ojaswin Mujoodescribed a potential way forward for the feature using an approach basedon writethrough, which effectively means that the kernel immediately writesthe data to disk instead of waiting for writeback from the page cache to occur. As might beexpected, there was quite a bit of discussion among the assembledfilesystems and storage developers during the combined sessions for thosetracks.