On Sun, Apr 16, 2000 at 05:13:39PM +0200, Jens Axboe wrote:
> On Sun, Apr 16 2000, Steve Dodd wrote:
> > /*
> > * Loop uses two requests, 1 for loop and 1 for the real device.
> > * Cut max_req in half to avoid running out and deadlocking.
> > */
> > if ((major == LOOP_MAJOR) || (major == NBD_MAJOR))
> > max_req >>= 1;
> >
> > This assumption presumably breaks down horribly for file-backed loop
> > devices? The numbers of requests that the filesystem is going to generate
> > to deal with one loop device request may well be >1. Does this sound
> > plausible to anyone or have I missed something?
>
> The assumption does indeed break down for file back devices, but that
> should not be a problem. The worst case scenario would just cause
> get_request to block, even though it would be safe to dish out a
> request.
Hmmm, I'm not clear on the working of the request queue stuff, but I don't
see why the comment above would apply to block-backed but not file-backed
loops. Surely the issue is that you can end up in a sitation where you need
one or more free requests to complete a request, there are no free
requests, and the only way to free one is to complete a request..
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This archive was generated by hypermail 2b29 : Sun Apr 23 2000 - 21:00:09 EST