On Sat, Jan 18, 2020 at 08:28:38PM +1100, Dave Chinner wrote: > I think it's pretty gross, actually. It makes the same mistake made > with locking in the old direct IO code - it encodes specific lock > operations via flags into random locations in the DIO path. This is > a very slippery slope, and IMO it is an layering violation to encode > specific filesystem locking smeantics into a layer that is supposed > to be generic and completely filesystem agnostic. i.e. this > mechanism breaks if a filesystem moves to a different type of lock > (e.g. range locks), and history teaches us that we'll end up making > a horrible, unmaintainable mess to support different locking > mechanisms and contexts. > > I think that we should be moving to a model where the filesystem > provides an unlock method in the iomap operations structure, and if > the method is present in iomap_dio_complete() it gets called for the > filesystem to unlock the inode at the appropriate point. This also > allows the filesystem to provide a different method for read or > write unlock, depending on what type of lock it held at submission. > This gets rid of the need for the iomap code to know what type of > lock the caller holds, too. I'd rather avoid yet another method. But I think with a little tweaking we can move the unlock into the ->end_io method.
