On Mon, 2 Sep 2002 Andries.Brouwer@cwi.nl wrote: > > HOWEVER, that disk change checking really should be done by > > the generic layers, and it should be done after the open() anyway > > (and not by the open) > > Are you sure? > I am inclined to think that this would be an undesirable change of > open() semantics. Traditionally, and according to all standards, > open() will return ENXIO when the device does not exist. Well, one reason I don't want the low-level drivers doing the media change checking is that there's more to media change than just checking the media. For example, the higher levels want to do a partition table re-read if the media really has changed. We do have this strange "bd_invalidated" thing for passing that information back, and maybe that is acceptable. It's a bit subtle, though. Another reason why it would be good to factor out media change from open() is that I can well imagine that somebody would want to do a "door open" ioctl on a device without a media, and we actually do kind of have that interface: opening with O_NDELAY historically means to not do the media change checks. And guess what? Because that test is done inside the low-level driver right now, it means that these O_NDELAY semantics aren't actually known or followed by most drivers, _and_ it means that the higher levels don't even realize that sometimes the media check hasn't gotten done at all (ie because the low-level "open()" is called only for the _first_ open, the higher levels right now won't even call "open()" at _all_ later on and so the media checks aren't done later when they should be). However, your ENXIO point is a good one, and implies that we really should have a more expressive "media_change()" function, so that if we'd factor out open()/media_check(), then we'd still get the right ENXIO thing. Linus - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
