Re: Current git --> kaboom [bisect] seems IDE related.

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Monday 11 February 2008, Sergei Shtylyov wrote:
> Bartlomiej Zolnierkiewicz wrote:
> 
> > From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
> > Subject: [PATCH] ide-disk: fix flush requests (take 2)
> 
> > commit 813a0eb233ee67d7166241a8b389b6a76f2247f9
> > Author: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
> > Date:   Fri Jan 25 22:17:10 2008 +0100
> 
> >     ide: switch idedisk_prepare_flush() to use REQ_TYPE_ATA_TASKFILE requests
> 
> > ...
> 
> > broke flush requests.
> 
> > Allocating IDE command structure on the stack for flush requests is not
> > a very brilliant idea:
> 
> > - idedisk_prepare_flush() only prepares the request and it doesn't wait
> >   for it to be completed
> 
> > - there are can be multiple flush requests queued in the queue
> 
> > Fix the problem (per hints from James Bottomley) by:
> > - dynamically allocating ide_task_t instance using kmalloc(..., GFP_ATOMIC)
> > - adding new taskfile flag (IDE_TFLAG_DYN)
> > - calling kfree() in ide_end_drive_command() if IDE_TFLAG_DYN is set
> >   (while at it rename 'args' to 'task' and fix whitespace damage)
> 
> > [ This will be fixed properly before 2.6.25 but this bug is rather
> >   critical and the proper solution requires some more work + testing. ]
> 
> > Thanks to Sebastian Siewior and Christoph Hellwig for reporitng the
> > problem and testing patches (extra thanks to Sebastian for bisecting
> > it to the guilty commmit).
> > 
> > Cc: Sebastian Siewior <ide-bug@ml.breakpoint.cc>
> > Cc: Christoph Hellwig <hch@infradead.org>
> > Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
> > Cc: Jens Axboe <jens.axboe@oracle.com>
> > Cc: Tejun Heo <htejun@gmail.com>
> > Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
> 
> Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
> 
> > Index: b/drivers/ide/ide-disk.c
> > ===================================================================
> > --- a/drivers/ide/ide-disk.c
> > +++ b/drivers/ide/ide-disk.c
> > @@ -590,20 +590,24 @@ static ide_proc_entry_t idedisk_proc[] =
> >  static void idedisk_prepare_flush(struct request_queue *q, struct request *rq)
> >  {
> >  	ide_drive_t *drive = q->queuedata;
> > -	ide_task_t task;
> > +	ide_task_t *task = kmalloc(sizeof(*task), GFP_ATOMIC);
> >  
> > -	memset(&task, 0, sizeof(task));
> > +	/* FIXME: map struct ide_taskfile on rq->cmd[] */
> > +	BUG_ON(task == NULL);
> > +
> > +	memset(task, 0, sizeof(*task));
> 
>     Why not kzalloc() then?

Well, yes.  However since the patch has been already merged upstream and it
is only a temporary solution I don't think it is worth doing it now (OTOH if
somebody sends me a patch I'll happily merge it).

Thanks,
Bart