Re: [PATCH 2.6.12.5 1/2] lib: allow idr to be used in irq context

[Luben Tuikov <ltuikov@yahoo.com>]

--- James Bottomley <James.Bottomley@SteelEye.com> wrote:
> On Sun, 2005-08-21 at 08:49 -0700, Luben Tuikov wrote:
> > The caller is the aic94xx SAS LLDD.  It uses IDR to generate unique
> > task tag for each SCSI task being submitted.  It is then used to lookup
> > the task given the task tag, in effect using IDR as a fast lookup table.
> > 
> > Yes, I'm also not aware of any other users of IDR from mixed process/IRQ
> > context or for SCSI Task tag purposes.
> 
> Just a minute, that's not what idr was designed for.  It was really
> designed for enumerations (like disk) presented to the user.  That's why
> using it in IRQ context hasn't been considered.

Hi James, how are you?

Is this the only use _you_ could find for a *radix tree*? ;-)
Since of course sd.c uses it just as an enumeration, according to
you this must be the only use? :-)

It was designed as a general purpose id to pointer translation
service, just as the comment in it says.

> However, there is an infrastructure in the block layer called the
> generic tag infrastructure which was designed precisely for this purpose
> and which is designed to operate in IRQ context.

James, I'm sure you're well aware that,
   - a request_queue is LU-bound,
   - a SCSI _transport_ (*ANY*) can _only_ address domain devices, but
     _not_ LUs.  LUs are *not* seen on the domain.

See the different associations?  Then why are you posting such emails?

Andrew, please apply this patch.

Thanks,
     Luben