[PATCH] [POWERPC] Fix viodasd driver with scatterlist debug

[PATCH] [POWERPC] Fix viodasd driver with scatterlist debug

[Benjamin Herrenschmidt]

The iSeries viodasd drivers does some very strange things with
scatterlists, one of these causing a BUG_ON to trigger when
scatterlist debugging is enabled due to initializing the
scatterlist with memset instead of sg_init_table().

This fixes it by using sg_init_table(). The rest of the stuff
it does to that poor list is still pretty awful but it will work.

I may look into fixing things in a nicer way some other time.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

 drivers/block/viodasd.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- linux-work.orig/drivers/block/viodasd.c	2008-03-12 10:25:55.000000000 +1100
+++ linux-work/drivers/block/viodasd.c	2008-03-12 10:39:38.000000000 +1100
@@ -528,8 +528,7 @@ static int block_event_to_scatterlist(co
 		numsg = VIOMAXBLOCKDMA;
 
 	*total_len = 0;
-	memset(sg, 0, sizeof(sg[0]) * VIOMAXBLOCKDMA);
-
+	sg_init_table(sg, VIOMAXBLOCKDMA);
 	for (i = 0; (i < numsg) && (rw_data->dma_info[i].len > 0); ++i) {
 		sg_dma_address(&sg[i]) = rw_data->dma_info[i].token;
 		sg_dma_len(&sg[i]) = rw_data->dma_info[i].len;

Re: [PATCH] [POWERPC] Fix viodasd driver with scatterlist debug

[Stephen Rothwell]

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Hi Ben,

On Wed, 12 Mar 2008 17:23:56 +1100 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
>
> The iSeries viodasd drivers does some very strange things with
> scatterlists, one of these causing a BUG_ON to trigger when
> scatterlist debugging is enabled due to initializing the
> scatterlist with memset instead of sg_init_table().
> 
> This fixes it by using sg_init_table(). The rest of the stuff
> it does to that poor list is still pretty awful but it will work.

Presumably this is also needed in 2.6.24.xx

-- 
Cheers,
Stephen Rothwell                    sfr@canb.auug.org.au
http://www.canb.auug.org.au/~sfr/

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Re: [PATCH] [POWERPC] Fix viodasd driver with scatterlist debug

[Benjamin Herrenschmidt]

On Wed, 2008-03-12 at 17:44 +1100, Stephen Rothwell wrote:
> Hi Ben,
> 
> On Wed, 12 Mar 2008 17:23:56 +1100 Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
> >
> > The iSeries viodasd drivers does some very strange things with
> > scatterlists, one of these causing a BUG_ON to trigger when
> > scatterlist debugging is enabled due to initializing the
> > scatterlist with memset instead of sg_init_table().
> > 
> > This fixes it by using sg_init_table(). The rest of the stuff
> > it does to that poor list is still pretty awful but it will work.
> 
> Presumably this is also needed in 2.6.24.xx

Possibly, though the problem only occurs when enabling scatterlist
debug, which distros don't do. Is it worth putting in a stable release ?

If yes, I'll submit it as soon as it hits upstream.

Cheers,
Ben.