Re: 2.6.9-rc1-mm5

[Jens Axboe]

On Wed, Sep 15 2004, Jens Axboe wrote:
> On Wed, Sep 15 2004, William Lee Irwin III wrote:
> > On Mon, Sep 13, 2004 at 01:50:03AM -0700, Andrew Morton wrote:
> > >>> +cfq-iosched-v2.patch
> > >>>  Major revamp of the CFQ IO scheduler
> > 
> > On Wed, Sep 15 2004, William Lee Irwin III wrote:
> > >> While editing some files while booted into 2.6.9-rc1-mm5:
> > >> # ----------- [cut here ] --------- [please bite here ] ---------
> > >> Kernel BUG at cfq_iosched:1359
> > 
> > On Wed, Sep 15, 2004 at 01:38:34PM +0200, Jens Axboe wrote:
> > > Hmm, ->allocated is unbalanced. What is your io setup like (adapter,
> > > etc)?
> > 
> > 2 Maxtor Atlas10K 10Krpm U320 disks attached to some aic7902's. No
> > binary or 3rd-party modules anywhere near the box' fs or even the
> > network the thing is on. lspci output follows.
> 
> Hmm, I can only see this happening if rq->flags has its direction bit
> changed between the allocation time and the time of freeing. I'll look
> over scsi and see if I can find any traces of that, don't see any
> immediately.

Can you try if this works?

--- linux-2.6.9-rc1-mm5/drivers/block/cfq-iosched.c~	2004-09-15 14:50:14.941876065 +0200
+++ linux-2.6.9-rc1-mm5/drivers/block/cfq-iosched.c	2004-09-15 14:51:09.889996813 +0200
@@ -195,6 +195,7 @@
 	unsigned int in_flight : 1;
 	unsigned int accounted : 1;
 	unsigned int is_sync   : 1;
+	unsigned int is_write  : 1;
 };
 
 static struct cfq_queue *cfq_find_cfq_hash(struct cfq_data *, unsigned long);
@@ -1353,12 +1354,12 @@
 		if (crq->io_context)
 			put_io_context(crq->io_context->ioc);
 
+		BUG_ON(!cfqq->allocated[crq->is_write]);
+		cfqq->allocated[crq->is_write]--;
+
 		mempool_free(crq, cfqd->crq_pool);
 		rq->elevator_private = NULL;
 
-		BUG_ON(!cfqq->allocated[rw]);
-		cfqq->allocated[rw]--;
-
 		smp_mb();
 		cfq_check_waiters(q, cfqq);
 		cfq_put_queue(cfqq);
@@ -1415,6 +1416,7 @@
 		crq->io_context = cic;
 		crq->service_start = crq->queue_start = 0;
 		crq->in_flight = crq->accounted = crq->is_sync = 0;
+		crq->is_write = rw;
 		rq->elevator_private = crq;
 		cfqq->allocated[rw]++;
 		cfqq->alloc_limit[rw] = 0;

-- 
Jens Axboe

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