On Tue, Jan 14, 2025 at 03:57:26PM -0800, Darrick J. Wong wrote: > Ok, let's do that then. Just to be clear -- for any RWF_ATOMIC direct > write that's correctly aligned and targets a single mapping in the > correct state, we can build the untorn bio and submit it. For > everything else, prealloc some post EOF blocks, write them there, and > exchange-range them. > > Tricky questions: How do we avoid collisions between overlapping writes? > I guess we find a free file range at the top of the file that is long > enough to stage the write, and put it there? And purge it later? > > Also, does this imply that the maximum file size is less than the usual > 8EB? I think literally using the exchrange code for anything but an initial prototype is a bad idea for the above reasons. If we go beyond proving this is possible you'd want a version of exchrange where the exchange partners is not a file mapping, but a cow staging record.
