Re: 2.5 Problem Status Report

Jens Axboe
2002-09-11T10:53:27Z

On Wed, Sep 11 2002, Oleg Drokin wrote:
> Hello!
>
> On Wed, Sep 11, 2002 at 12:29:26PM +0200, Jens Axboe wrote:
>
> > > ok I see the bug. it's due to the imbalanced nature of ide_map_buffer()
> > > vs ide_unmap_buffer(). i'll cook up a fix right away.
> > Does this make it work?
>
> No. It fails exactly like without the patch.

Hmm, ok I'll try and reproduce it here then.

> > --- include/linux/ide.h~ 2002-09-11 12:27:14.000000000 +0200
> > +++ include/linux/ide.h 2002-09-11 12:27:29.000000000 +0200
> > @@ -597,9 +597,10 @@
> > return rq->buffer + task_rq_offset(rq);
> > }
> >
> > -extern inline void ide_unmap_buffer(char *buffer, unsigned long *flags)
> > +extern inline void ide_unmap_buffer(struct request *rq, char *buffer, unsigned long *flags)
> > {
> > - bio_kunmap_irq(buffer, flags);
> > + if (rq->bio)
> > + bio_kunmap_irq(buffer, flags);
> > }
> >
> > /*
>
> Perhaps you forgot to make sure rq->bio is zeroed on unmapping/freeing?

rq->bio must not be zeroed or free'd or anything like that. ok I see
what happens now. does this patch work for you? just back out the other
patch first (well you don't have to, but might as well).

# This is a BitKeeper generated patch for the following project:
# Project Name: Linux kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.639 -> 1.640
# include/linux/bio.h 1.17 -> 1.18
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 02/09/11 axboe@burns.home.kernel.dk 1.640
# clean up with bio_kmap_irq() thing properly. remove the micro optimization
# of _not_ calling kmap_atomic() if this isn't a highmem page. we could
# keep that and do the inc_preempt_count() ourselves, but I'm not sure
# it's worth it and this is cleaner.
# --------------------------------------------
#
diff -Nru a/include/linux/bio.h b/include/linux/bio.h
--- a/include/linux/bio.h Wed Sep 11 12:57:45 2002
+++ b/include/linux/bio.h Wed Sep 11 12:57:45 2002
@@ -215,17 +215,11 @@
{
unsigned long addr;

- local_save_flags(*flags);
-
- /*
- * could be low
- */
- if (!PageHighMem(bio_page(bio)))
- return bio_data(bio);
-
/*
- * it's a highmem page
+ * might not be a highmem page, but the preempt/irq count
+ * balancing is a lot nicer this way
*/
+ local_save_flags(*flags);
local_irq_disable();
addr = (unsigned long) kmap_atomic(bio_page(bio), KM_BIO_SRC_IRQ);

--
Jens Axboe