On Fri, Jul 20 2001, Linus Torvalds wrote: > > > On Fri, 20 Jul 2001, Jens Axboe wrote: > > > > > The paging stuff doesn't use any of this. The paging stuff use the page > > > cache lock bit, and always has. > > > > Paging still hits a request, I assumed that's what the (really really) > > old comment meant to say. > > No. Tha paging stuff (and _all_ regular IO) uses a regular request, with a > NULL waiter. That's the normal path. That normal path depends on the > buffer heads associated with the requests and their "bh->b_end_io()" > function marking other state up-to-date, and then waits on the page being > locked. This is perfectly clear. I'm saying 'paging uses a request just like any other I/O', and you seem to disagree and restate the same thing?! In fact the lower layers have no way of knowing what is what, paging or not. > The req->sem (and now req->completion) thing is a very different thing: it > is a "we are waiting for this particular request", and is used when it's > not really IO and doesn't have a bh, but something that has side effects. > Like an ioctl that causes a special command to the disk to change some > parameters, or query the size of the disk or something. Ditto! Are you reading what I write? > So the comment has just always been wrong, I think. It may be that the > original swapping code was doing raw requests instead of real IO, so maybe > the comment was actually correct back in 1992 or something. My memory > isn't good enough.. Good, so now you agree that the corrected comment (as per pre9) is crap, and the patch I sent that changes the wording to: "Ok, this is an expanded form so that we can use the same request for paging requests." is so much better than _you_ mixing ->waiting and ->sem into this paging or non-paging pool? But in fact the whole comment block should just be removed. It gives no useful or additional information. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [EMAIL PROTECTED]
