Re: SCSI tape crashes (was Re: BUG() in asm/pci.h:142 with 2.4.13)

Re: SCSI tape crashes (was Re: BUG() in asm/pci.h:142 with 2.4.13)

[Dan Maas]

> Can people try out this patch?  I believe this will fix the bug.
> + tb->sg[0].page = NULL;
>   if (tb->sg[segs].address == NULL) {

For the sake of making this clear to other kernel hackers (I got bitten by
it too) - starting with 2.4.13 you must zero out the fields of struct
scatterlist that you are not using. i.e. it is no longer sufficient to
simply set sg.address and sg.length, because junk might still be present in
the new sg.page field, and pci_map_*() will BUG() if both sg.address and
sg.page are non-zero.

Regards,
Dan

Re: SCSI tape crashes (was Re: BUG() in asm/pci.h:142 with 2.4.13)

[Jens Axboe]

On Tue, Oct 30 2001, Dan Maas wrote:
> > Can people try out this patch?  I believe this will fix the bug.
> > + tb->sg[0].page = NULL;
> >   if (tb->sg[segs].address == NULL) {
> 
> For the sake of making this clear to other kernel hackers (I got bitten by
> it too) - starting with 2.4.13 you must zero out the fields of struct
> scatterlist that you are not using. i.e. it is no longer sufficient to
> simply set sg.address and sg.length, because junk might still be present in
> the new sg.page field, and pci_map_*() will BUG() if both sg.address and
> sg.page are non-zero.

True, perhaps we should add a init_sg or something like that.

-- 
Jens Axboe

Re: SCSI tape crashes

[David S. Miller]

   From: Jens Axboe <axboe@suse.de>
   Date: Wed, 31 Oct 2001 09:46:50 +0100
   
   How is this different from my init_sg proposal? :-). The above looks
   fine to me, I just think it is important that we take care of this.
   
My impression was that you wanted to do something like:

	sgl = kmalloc();
	init_sg(sgl, nents);

	for_each_ent() {
		... existing code ..
	}

If what you really meant was semantically identicaly to what I have
proposed, I'm completely in agreement with it.  Please submit patches.

Franks a lot,
David S. Miller
davem@redhat.com

Re: SCSI tape crashes

[Jens Axboe]

On Wed, Oct 31 2001, David S. Miller wrote:
>    From: Jens Axboe <axboe@suse.de>
>    Date: Wed, 31 Oct 2001 09:46:50 +0100
>    
>    How is this different from my init_sg proposal? :-). The above looks
>    fine to me, I just think it is important that we take care of this.
>    
> My impression was that you wanted to do something like:
> 
> 	sgl = kmalloc();
> 	init_sg(sgl, nents);
> 
> 	for_each_ent() {
> 		... existing code ..
> 	}
> 
> If what you really meant was semantically identicaly to what I have
> proposed, I'm completely in agreement with it.  Please submit patches.

Yep, init_sg_entry is probably a better name... I'll hack up and submit
soonish.

-- 
Jens Axboe

Re: BUG() in asm/pci.h:142 with 2.4.13

[Jens Axboe]

On Thu, Oct 25 2001, Christian Hammers wrote:
> Hello
> 
> On Thu, Oct 25, 2001 at 01:11:07PM +0200, Jens Axboe wrote:
> > > 2.4.13 was the easiest one to reproduce: when starting the tape backup
> > > to a HP DDS3/DAT Streamer (C1537A) via a Adaptec SCSI Controller 
> > > (Adaptec 7892A in /proc/pci) on a Gigabyte GA-6VTXD Dual Motherboard with
> > > two PIII and 2GB of RAM it crashed immediately with the error attached
> > > below. The machine was under "stresstest-simulation" load at this time.
> 
> > Could you try this patch and see if it fixes the pci.h BUG at least?
> This patch did not prevent the crash. Again immediately after rewinding the
> tape when it began to write. I'll try now the 2.4.12-ac6... and it works.

Ok, someone else is meddling with the scatterlist then. I'll take a 2nd
look.

-- 
Jens Axboe

SCSI tape crashes (was Re: BUG() in asm/pci.h:142 with 2.4.13)

[David S. Miller]

   From: Jens Axboe <axboe@suse.de>
   Date: Thu, 25 Oct 2001 19:32:48 +0200

   On Thu, Oct 25 2001, Christian Hammers wrote:
   > This patch did not prevent the crash. Again immediately after rewinding the
   > tape when it began to write. I'll try now the 2.4.12-ac6... and it works.
   
   Ok, someone else is meddling with the scatterlist then. I'll take a 2nd
   look.

Can people try out this patch?  I believe this will fix the bug.

--- drivers/scsi/st.c.~1~	Sun Oct 21 02:47:53 2001
+++ drivers/scsi/st.c	Thu Oct 25 17:23:45 2001
@@ -3233,6 +3233,7 @@
 				break;
 			}
 		}
+		tb->sg[0].page = NULL;
 		if (tb->sg[segs].address == NULL) {
 			kfree(tb);
 			tb = NULL;
@@ -3264,6 +3265,7 @@
 					tb = NULL;
 					break;
 				}
+				tb->sg[segs].page = NULL;
 				tb->sg[segs].length = b_size;
 				got += b_size;
 				segs++;
@@ -3337,6 +3339,7 @@
 			normalize_buffer(STbuffer);
 			return FALSE;
 		}
+		STbuffer->sg[segs].page = NULL;
 		STbuffer->sg[segs].length = b_size;
 		STbuffer->sg_segs += 1;
 		got += b_size;

Re: SCSI tape crashes (was Re: BUG() in asm/pci.h:142 with 2.4.13)

[Jeff V. Merkey]

David,

Is this waht's causing the earlier bug I reported in 2.4.10?  If so 
where is this patch so I can see if it fixes the problem.

Thanks,

Jeff


On Thu, Oct 25, 2001 at 05:25:41PM -0700, David S. Miller wrote:
>    From: Jens Axboe <axboe@suse.de>
>    Date: Thu, 25 Oct 2001 19:32:48 +0200
> 
>    On Thu, Oct 25 2001, Christian Hammers wrote:
>    > This patch did not prevent the crash. Again immediately after rewinding the
>    > tape when it began to write. I'll try now the 2.4.12-ac6... and it works.
>    
>    Ok, someone else is meddling with the scatterlist then. I'll take a 2nd
>    look.
> 
> Can people try out this patch?  I believe this will fix the bug.
> 
> --- drivers/scsi/st.c.~1~	Sun Oct 21 02:47:53 2001
> +++ drivers/scsi/st.c	Thu Oct 25 17:23:45 2001
> @@ -3233,6 +3233,7 @@
>  				break;
>  			}
>  		}
> +		tb->sg[0].page = NULL;
>  		if (tb->sg[segs].address == NULL) {
>  			kfree(tb);
>  			tb = NULL;
> @@ -3264,6 +3265,7 @@
>  					tb = NULL;
>  					break;
>  				}
> +				tb->sg[segs].page = NULL;
>  				tb->sg[segs].length = b_size;
>  				got += b_size;
>  				segs++;
> @@ -3337,6 +3339,7 @@
>  			normalize_buffer(STbuffer);
>  			return FALSE;
>  		}
> +		STbuffer->sg[segs].page = NULL;
>  		STbuffer->sg[segs].length = b_size;
>  		STbuffer->sg_segs += 1;
>  		got += b_size;
> -
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Re: SCSI tape crashes

[David S. Miller]

   From: "Jeff V. Merkey" <jmerkey@vger.timpanogas.org>
   Date: Thu, 25 Oct 2001 19:26:48 -0700
   
   Is this waht's causing the earlier bug I reported in 2.4.10?  If so 
   where is this patch so I can see if it fixes the problem.
   
The patch was in the email, can't you read? :-)
(You even quoted the patch in your reply!)

Anyways, my patch isn't relevant to your problem since the
bug I am fixing only can exist in 2.4.13 and later kernels.
Sorry.

   
   On Thu, Oct 25, 2001 at 05:25:41PM -0700, David S. Miller wrote:
   > Can people try out this patch?  I believe this will fix the bug.
   > 
   > --- drivers/scsi/st.c.~1~	Sun Oct 21 02:47:53 2001
   > +++ drivers/scsi/st.c	Thu Oct 25 17:23:45 2001

Franks a lot,
David S. Miller
davem@redhat.com

Re: SCSI tape crashes

[Jeff V. Merkey]

David,

Thanks.  I'll wait to hear from Kai since it looks like something
related to his code.  I did find the patch, but was using mutt,
and you were correct, it was attached at the end of the email.

:-)

Jeff


On Thu, Oct 25, 2001 at 06:32:48PM -0700, David S. Miller wrote:
>    From: "Jeff V. Merkey" <jmerkey@vger.timpanogas.org>
>    Date: Thu, 25 Oct 2001 19:26:48 -0700
>    
>    Is this waht's causing the earlier bug I reported in 2.4.10?  If so 
>    where is this patch so I can see if it fixes the problem.
>    
> The patch was in the email, can't you read? :-)
> (You even quoted the patch in your reply!)
> 
> Anyways, my patch isn't relevant to your problem since the
> bug I am fixing only can exist in 2.4.13 and later kernels.
> Sorry.
> 
>    
>    On Thu, Oct 25, 2001 at 05:25:41PM -0700, David S. Miller wrote:
>    > Can people try out this patch?  I believe this will fix the bug.
>    > 
>    > --- drivers/scsi/st.c.~1~	Sun Oct 21 02:47:53 2001
>    > +++ drivers/scsi/st.c	Thu Oct 25 17:23:45 2001
> 
> Franks a lot,
> David S. Miller
> davem@redhat.com