Re: bio_chain: proposed solution for bio_alloc failure and large IO simplification

From: Adam J. Richter (
Date: Sat Jun 15 2002 - 04:10:53 EST

>> So, I need a fourth location at in generic_make_request
>> just before the call to q->make_request_fn, like so:
>> if (q->make_request_fn != __make_request) {
>> int flags;
>> spin_lock_irqsave(q->lock, flags);
>> clear_hint(bio);
>> spin_unlock_irqrestore(q->lock, flags);
>> }
>> ret = q->make_request_fn(q, bio);

>Irk, this is ugly. But how you are moving away from the initial goal (or
>maybe this was your goal the whole time, just a single merge hint?) of
>passing back the hint instead of maintaing it in the queue. So let me
>ask, are you aware of the last_merge I/O scheduler hint? Which does
>exactly this already...

        The code that I think I more or less have in my head has not
changed (aside from that fourth test).

        Although I was not aware of q->last_merge, I see that it is
not what I want. I want up to one hint per request, for the last bio
in the request. bi_hint would be null for all bio's except possibly
the last bio in a request. I do not want just one hint per queue.

        If it is unclear what I mean, perhaps I really need to code it
up to explain it. and we can discuss it from there.

Adam J. Richter __ ______________ 575 Oroville Road \ / Milpitas, California 95035
+1 408 309-6081 | g g d r a s i l United States of America
                         "Free Software For The Rest Of Us."
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This archive was generated by hypermail 2b29 : Sat Jun 15 2002 - 22:00:33 EST