On Thursday February 19, nathapl@cs.okstate.edu wrote: > Yes, I think that clears it up. > > So, a single stripe (or even a single chunk) could certainly have both > outstanding read and write requests, but they are guaranteed to not be > overlapping. > > Is it also safe to assume that you'd never have outstanding, overlapping > write requests either (since order is not maintained within the bio > list)? I think the code tries to keep writes in order - at least it used to. Maybe it doesn't in 2.6 It would also warn if there were two concurrent writes. This warning did trigger a couple of times, and it was always due to a bug in the filesystem. > > I always thought the drive/device driver was responsible for keeping > requests in order. But you're saying that's been delegated to the > filesystem, correct? Device drivers are expected to re-order requests to make best use of the device, though re-ordering two requests for the same block doesn't make a lot of sense. But yes, the filesystem is expected not to do anything silly, and have two concurrent IO requests for the same block fits in the category of "silly". NeilBrown - 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
