Jeff Layton <jlayton@xxxxxxxxxx> writes: >> >> Would it be of any benefit to keep a distinct ctime_floor in each >> super block instead? >> > > Good question. Dave Chinner suggested the same thing, but I think it's > a potential problem: > > The first series had to be reverted because inodes that had been > modified in order could appear to be modified in reverse order with the > right combination of fine and coarse grained timestamps. With the new > floor value, that's no longer possible, but if we were to make it per- > sb then it becomes possible again with files in different filesystems. > > This sort of timestamp comparison is done by tools like "make", and > it's rather common to keep built objects in one location and generate > or copy source files to another. My worry is that managing the floor as > anything but a global value could cause regressions in those sorts of > workloads. Have you considered the interactions with time name spaces? It seems you may need a floor for each, otherwise if the floor is set by some name space with a more future time the other users lose out. Also there's the issue to what happens if time gets set backwards. -Andi
